PPaaiinnttiinnggssObjectives page 111

Introduction page 111

Structure of paintings page 111

What are the most common types and causes of damage? page 114

The dos and donts of handling paintings page 115

Framing paintings page 118

Hanging paintings securely page 120

Ideal conditions for the storage and display of paintings page 121

General storage and display guidelines page 122

Summary of conditions for the storage and display page 124

Paintings in Australias climatic zones page 124

MORE ABOUT PAINTINGS

Keying out page 126

What can go wrong with a stretcher and what you can do page 126

Handling straps page 126

Labels and inscriptions page 126

For further reading page 126

Self-evaluation quiz page 127

Answers to self-evaluation quiz page 129

Paintings 111

Objectives

At the end of this chapter you should:

be familiar with the structure and componentsof various types of paintings;

understand possible sources of damage forpaintings; and

know how to frame and hang a painting toensure proper protection from damage.

Introduction

Early frames were simple affairs. They were usuallymade from single pieces of wood which weregenerally either gilded or left plain. They wereoriginally used to protect the fragile edges ofpanel altarpieces. Then, as paintings became moresecular, frames became more decorative and weredesigned to complement the architecturesurrounding them.

So we can see that the frame on a painting servestwo purposes:

it has an aesthetic functionit enhanceselements of the painting and unifies thepainting with its environment; and

it also serves as a protective device, providinga physical barrier between the environmentand the artwork.

Additional protective components can be added tothe frame to:

protect the back and front of the artworkfrom knocks and abrasions;

minimise the effects of vibration andmovement;

enable the work to be hung securely;

facilitate handling; and

protect the work from dust and pollution.

Many paintings, however, do not have frames, orthey have flimsy and inadequate original frames.Such works are more difficult to protect; but if you

keep the basic principles in mind, you can provideprotection for all paintings.

It is important to note that not all frames areprotective. While a good-quality, well-constructedframe will provide protection for a painting, apoorly made frame, or one which is not properlyfitted to the work, can cause damage.

This section discusses good protective framingpractice; it looks at the types of framing systemswhich are relevant for each type of paintingstructure and gives general information to helpyou prolong the lives of the paintings in your care.

Structure of paintings

In order to discuss the possible damage topaintings and to take steps to reduce that damage,it is important to know something of the structureof paintings and the range of materials which canbe used to produce them.

Paintings consist at the very least of two layers:

the support layer on which the image layerreststhis can be canvas, wooden panelling,or Masonite; and

the image layeroil paint, acrylic paint orpaint in combination with other materials.

If the support and the image layer are not securelybonded, then any movement in the support willdamage the paint layer.

Most paintings are more complex than this andhave many more parts in their structure. Atraditional painting on canvas will usually have:

a sized supportin many cases canvas sizedwith skin glue;

a priming or ground layer;

the paint or image layer;

a varnish layer; and

an auxiliary support which provides physicalsupport for the support layer.

112 Paintings

Supports

The term support refers to the layer which carriesor supports the paint or image layer.

Paintings can be produced on any type of support.

Traditionally, most supports have been made fromlinen canvas or wooden panels.

In the 20th century, linen canvas has often beenreplaced by cotton duck, and wooden panels withcompressed particle board such as Masonite.

Artists are creative beings and there are a widerange of materials which have been used in thename of art! They include:

rigid wooden supports such as particle boardproducts like chipboard or Masonite or thetraditional wooden panels;

rigid supports made from a range of othermaterials such as glass or metal;

lightweight cottons or Nylon looselystretched, which some artists use to give afeeling of fluidity;

paper glued onto canvas; canvas.

The priming and ground layers

Priming and ground layers are used to:

provide a good physical support for the paintlayer; and

provide a surface to mask the texture of thesupport. If there are no priming and groundlayers, it may be possible to see the textureof the support through the paint.

A good ground layer physically keys in the paintlayer as it is slightly porous.

The ground layer, however, should not be veryabsorbent. It must be slightly resistant to thepaint, otherwise brushstrokes will not be clear andwill sink into the ground.

The support is sized, usually with rabbit-skin glue;and then the ground layers are applied.

Works on canvas usually have two ground layers,although having one or three is not uncommon.

If the ground layers are not well bonded to thesupport, then movement of the support may leadto a delamination or cracking of the ground.

In addition, if the ground layers are not properlyprepared or do not provide a secure base for thepaint layerthey may not be porous enough tohold the paint for examplethen problems withthe paint layer will occur.

A traditional ground was usually made from leadwhite or a chalk gesso. Acrylic grounds are nowcommon. While grounds are generally white, someartists, John Constable for instance, favouredcoloured grounds.

The layers of size and ground can be very reactive;and if they are wet they will cause severe damageto the paint layers.

The paint layer

The paint layer or image layer can be made up ofpaint and a number of other materials, includingpaper or found objects in collage.

This painting of the DestituteAsylum in Adelaide has beenremoved from its stretcher fortreatment. The canvas supportcan be clearly seen around theedges of the image.

Photograph courtesy ArtlabAustralia, reproduced withpermission of the Historic Trustof South Australia

This icon is painted on awooden panel.

Photograph courtesyArtlab Australia,reproduced withpermission of Mr Kostya Prosylis

Paintings 113

Oil paint is the traditional paint medium, however,in more recent times synthetic materials such asacrylics and alkaloid resins are common.

Oil paint dries by evaporation, and then by achemical crosslinking process. This means that itbecomes less flexible as it ages.

The varnish layer

Varnishes are applied on top of the paint layer.They are applied as liquids and dried to produceclear, tough films.

They protect the paint layerto a degreedepending on their compositionfrom physicaldamage and chemical attack.

Varnishes also have an aesthetic function: theysmooth out the unevenness of the paint surface sopreventing light being scattered when it isreflected. This gives the colours in the work amore saturated appearancethe colours appeardarker and have greater depth.

It is important to note that further paint layersand transparent coloured layers known as glazesmay be applied over the varnish layer. Thistechnique produces an illusion of depth.

A range of materials have been used as varnishes.Among the most stable are:

Dammar dissolved in turpentinethis is anexample of a traditional varnish made fromnatural resins dissolved in solvents; and

acrylic resins dissolved in petroleum spirit.

Auxiliary supports

Traditionally, paintings on canvas have beenattached to auxiliary supportsusually a stretcheror a strainerusing staples or tacks.

The purpose of the auxiliary support is to securethe canvas and keep it taut. It is important tokeep the support as taut as possibleloosesupports will undergo far greater dimensionalchange in response to fluctuations and so aremuch more vulnerable to damage.

A stretcher differs from a strainer in that thecorners of a stretcher can be keyed out, therebytightening the canvas.

The corners of the stretcher are adjustable,enabling the dimensions of the stretcher to beenlarged to tighten the canvas. This is done bypushing the keys further into the keyholes, andexpanding the corners.

CAUTION:

Because inappropriate tightening of the canvas can cause damage, you need to know what you are doing, or be shown by a conservator, before

you commence keying out a work.

A strainer is a wooden frame which does not haveadjustable corners. Therefore if the canvasbecomes loose over time, it cannot be made tautagain without being re-stretchedthis is a job fora conservator.

Examples of other auxiliary supports include:

cradles placed on the backs of panel paintings;and

wooden frames used to secure Masonitesupports.

A stretchernote the keys in the corners.

Photograph courtesy of Artlab Australia

A strainer.

Photograph courtesy ofArtlab Australia

114 Paintings

What are the most commontypes and causes of damage?

As with most cultural material, the deterioration ofpaintings is caused by physical damage andchemical activityusually in combination.

Physical damage is very obvious and includes:

Tears and breaks. For example, many canvaspaintings are damaged when people are workingnear the paintings and accidentally put the handleof a broom, a ladder etc. through the canvas. Thisis not uncommon.

Cracking of varnish and paint layers because ofmovement of the support, due to:

vibration during handling and travel; impact when a painting is dropped, knocked

or falls off a wall; and fluctuations in relative humidity. Both canvas

and wood take up and release moisture as therelative humidity fluctuates. This producesdimensional changes which can lead tocracking of the paint and varnish.

Separation of the different layers of the paintingstructure. This can because by fluctuations inrelative humidity and/or to impact.

Softening of the varnish layer in hightemperatures. The varnish can become sticky andany dust or dirt on the surface may becomepermanently attached to the painting.

Warping of the stretcher due to extremes andfluctuations in relative humidity, and lack ofproper support in storage or display.

Insect attack, for example, wooden stretchers canbe attacked by borers and canvas and cardboardsupports can be attacked by silverfish.

Dust and dirt can distort paintings if allowed tocollect between the lower stretcher bar and thecanvas. This can lead to distortion of the paintlayer. Dust will also take up and hold moisture,thus creating a localised area of high humiditythis can lead to localised dimensional change andoverall distortion.

Chemical deterioration can be very damaging andwill often mar the appearance of paintings.Chemical damage to paintings includes:

Colour change and fading of pigments whenexposed to light and UV radiation. Oil paintingsare often considered to be quite stable in light,but some pigments and glazes are particularlysusceptible to light damage.

Discolouration of the varnish. This may be due toexposure to light and UV radiation and/or becauseof the natural ageing of the particular varnish.

This pre-treatment photograph shows severe tears inthe canvas support of a painting.

Photograph courtesy Artlab Australia

This stretcher had been exposed to quite extremefluctuations in relative humidity causing it to warpseverely. In time, this resulted in the structuralbreakdown of the stretcher with obvious damage to the canvas support.

Photograph courtesy Artlab Australia

Paintings 115

Deterioration of some components of the paintingwhere poor-quality materials have been used orwhere the painting has not been properlystructured.

Reactions between incompatible components ofthe painting. This is more likely to occur when thepainting is a complex collage made up of acombination of paint and a number of othermaterials.

Cracking or movement of paint layers due to theunstable nature of one or more of the componentsof the painting. Bituminous additives in paint arean example of one of these unstable materials.

Mould attack. All components of paintings aresusceptible to mould in high-humidity conditions.

Changes due to the action of atmosphericpollutants, for example:

colour change in pigments;

breaking down of structural componentsleading to loss of strength; and

alterations in solubility characteristics ofpaint films and varnishes.

The dos and donts of handling paintings

Because paintings are such complex structures, itis important to understand correct handlingprocedures. Remember, a paint surface may receivea knock and appear to be unharmed. But over timemovement in the canvas will cause this weakenedarea to crack. It can take a decade or longer for acrack to appear after a knock.

Handling stretched paintings and framed works

It is very difficult to properly support and protectpaintings if you carry more than one at a time. Itis important that you always carry only onepainting at a time.

Before moving any painting:

Check that there is no flaking paint and that thework is secure in its frame.

Check that there are no loose pieces on the frame.If there are, consult a conservator.

Make sure you know where you are going with thework, and you have checked your path to makesure it is clear and all doors are open, or thatthere are people available to assist.

If there is flaking paint on the painting, leave itface-up and consult a conservator. If you have tomove it, carry it flat and face-up, so that youdont lose any paint while you are moving.

Do not touch the canvas or the paint surfacedirectly.

Wearing white, cotton gloves while handlingpaintings and frames is advisable, particularly

This photograph taken during treatment shows clearlythe degree to which varnish can discolour and alterthe appearance of a painting.

Photograph courtesy Artlab Australia, reproduced withpermission of Mr Paul Fitzgerald

The appearance of this painting was marred by patchesof mould growth.

Photograph courtesy Artlab Australia, reproduced withpermission of B. W. Johns

116 Paintings

when handling gilded frames. Gilt surfaces can bepermanently marked by perspiration and oils fromyour skin.

If your canvas painting does not have a backboard,check that the stretcher wedges are secured. Theycan do a lot of damage if they fall between thecanvas and the stretcher.

Always hold paintings at points where the frame isstrong. Ornate frames are especially vulnerable todamage. Never grip them by any of the ornateareas of the frame, because they may not be verystrong and could break.

Never carry a painting by the top of its frame orstretcher. Carry it with one hand beneath and onehand at the side; or if it is small, one hand oneach side. Carrying frames from the top member isdangerous and can cause the mitres to becomeloose and decorative elements to dislodge.

If the work is unframed, it is better to move itusing handling straps or a travelling frame. Both ofthese allow you to carry paintings without theneed for you to touch the paint surface. If neitherof these are available, then carry unframed,stretched paintings on the outer edges withouttouching either the front or back of the canvas.Dont allow your fingers to touch the paint surface.

Dont put your fingers around the stretcher bars, orbetween the stretcher and the canvas, because youcould cause the canvas to bulge and the paint tocrack and flake in that area.

Remember to carry wrapped paintings with extracare, because you cannot see what you aretouching.

Before putting a painting down on the floor,ensure that there are padded, wooden blocks orfoam blocks in place where you wish to place it.These blocks provide a softer surface than the floorand keep paintings up off ground-level.

When you put the painting down, do not set itdown on one corner: always set it down along onecomplete edge.

A large painting must be moved by two peopleregardless of the weight involved. Never attemptto move a large painting alone. When two peopleare working together, make sure you both agree onthe way the painting is to be moved.

If you are moving paintings on a trolley, it is wiseto have two people to accompany the loadedtrolley. With two people, you have one to hold thepaintings in place while the other can open doors,etc. If one person tries to do everything at once,accidents are likely to happen.

Trolleys should be padded to prevent damage toframes.

If any damage should occur during the move,carefully collect and save any pieces, no matterhow smalleven tiny paint flakesand documentthe damage.

If you are hanging a painting, check that thehanging devices and the wall on which thepainting is to be hung are secure. Paintings can bevery badly damaged if they fall off the wall.

When you are framing or deframing a painting,make sure that you have a clean, padded surfaceon which to place both the frame and thepainting.

Moving framed paintings with glazing

Glazing usually refers to the glass or Perspexsometimes used in framing systems for paintings.

Glazed artworks should be carried with care:

acrylic glazing such as Perspex is easilyscratched; and

glass can break if dropped or knocked.

Handling strapsattached to the backof a backing board.

Photograph courtesyArtlab Australia

Paintings 117

If you are transporting paintings glazed with glass,tape the front of the glass with masking tape. Thiswill hold the pieces of the glass together, should itbreak, and lessen the risk of damage to the work.

The tape should be on the glass only, and shouldnot extend onto the frame because it can removepaint or other finishes when it is removed.

For small frames, one strip of tape vertically in thecentre of the glass, one horizontally and one stripof tape on each diagonal will be sufficient. Largerframes will need more.

Fold the tape back on itself at one end of eachstrip, to provide yourself with a grip for easierremoval of the tape.

Remove the tape as soon as possible after themove. Pull the tape off at a very low angle, so thatyou dont make the glass flex too much. This couldcause it to break. Remember, pull gently.

It is better not to tape Perspex or Plexiglas as:

the tape can be very difficult to remove;

it can leave adhesive residues which cannotbe cleaned away; and

there is, after all, really no need to tapePerspex or Plexiglas because they wont breakand shatter like glass.

Handling unstretched paintings

Not all paintings are stretched and framed. Manypaintings are now sold and kept, unstretched.Because the canvas is not kept taut, thesepaintings are particularly vulnerable to damagecaused by movement of the support.

Unstretched paintings can be quite difficult tohandle. If they are allowed to flop or move toomuch, the paint can begin to come away from thesurface of the canvas; so it is very important thatunstretched paintings are well supported.

If the paintings are small enough to be movedflat, put a rigid support under them so that theycan be handled easily without flopping anddistorting. A sheet of Foam Cor or a strong mountboard is suitable.

Larger unstretched paintings may need to be rolledto be carried, and transported.

If you are going to roll a painting it is veryimportant that paintings are rolled the rightwaypainted side outand that they are properlyinterleaved and the roller properly padded. If thepaint layer is on the inside when the painting isrolled, the paint will become compressed and willdevelop creases, which will remain in the paintingafter it has been unrolled.

T he roller should be as large as possible ind ia meterat least 200mm. For example, a verylarge acrylic painting which travelled to the USA inthe South Australian Museums Dreamingsexhibition was rolled on a roller more than onemetre in diameter. The larger the painting, thelarger the diameter of the roller should be.

Rollers should be covered with a layer ofpaddingeither a polyethylene foam such asPlastazote, or Dacron wadding covered with cleanwhite cotton fabricto compensate for anyirregularities in the paintings thickness.

It is best to roll the painting with an interleavinglayer of Tyvek to prevent any transfer of pigment.The Tyvek should be larger in length and widththan the painting.

The rolled and wrapped painting should be tiedfirmly, but not tightly, with cotton tape in severalplaces along the roll.

Rollers can be specially made of lightweightmaterials, such as:

R i b l o c. Ask the ma nu fa c t u rer to ma ke the ro l l e rwith the ribs on the ins ide, if possible; and

PVC pipe. A 300mm diameter pipe is a goodsize for most works.

If you have to roll more than one painting on aroller, the paintings should be laid out flat andinterleaved with Protecta Foam. Once this is done,the paintings should be rolled onto the roller all atthe same time. Remember, all the paintings shouldbe paint-side out.

118 Paintings

Framing paintings

Framing for protection

As already noted, frames are important protectivedevices. Good framing is as much common sense asanything else but certain principles should be keptin mind.

The painting needs to be protected at the frontand back if possible, from damage caused by:

knocks and abrasions;

dust and pollution;

environmental fluctuations; and

biological pests.

For this reason you should provide a backing boardfor your paintings, and consider glazing works.

The painting needs to be protected from vibrationas much as possible. For this reason the frameneeds to hold the work firmly but allow somecushioning, so that if the painting is knocked theframe will take the force of the impact. Thepainting will need to be keyed out if the canvasbecomes loose. Make sure that the painting doesnot fit too tightly in the frame.

Other considerationsaesthetics and history

When making any decisions about whether toretain, replace or repair an original frame, it isimportant to understand the history of thepainting and its frame.

Many artists consider the frame to be an importantpart of the presentation of their work. For some itis even an intrinsic element. Keep in mind thatframe styles reflect the period of the artworkand/or the design of the individual artist.

It is important to note that in some instances theframe will have been conceived as part of theoriginal aesthetic of the work. For example:

the 1889 9 x 5 exhibition is perhaps themost well known Australian example of artistsmaking very specific decisions about theirframes;

many contemporary artists have very definiteideas on the framing of their work; and

Fiona MacDonald is an example of acontemporary Australian artist who uses theframe as part of the aesthetic of her work. Toreplace the frame would be akin to replacingpart of the work.

Many frames are important aesthetic statements intheir own right and may be valuable historic items.For example, framemakers Robin Hood and IsaacWhitehead were important Australian framemakers.An original frame by these framemakers is likely tobe worth a substantial amount of money, certainlyin the tens of thousands for a large, ornate framein good original condition.

In other instances the artist may have no interestin the frame at all. Works may be sold unframed orthe artist may simply have a trade order with aframer.

Decisions about framing and reframing, therefore,need to be made carefully and with a properunderstanding of all the issues.

Backing boards

Backing boards protect the painting by providing aphysical barrier between the back of the paintingand the external environment.

It is obvious that one of the most importantthings you can do to protect a painting is toprovide it with a snugly fitting backing board. A backing board will help to protect against:

knocks;

changes in temperature and humidity;

the effects of atmospheric pollution;

lodgement and build-up of dust;

insect and mould attack.

Various types of material can be used for backingboards. It is important to choose a material whichis lightweight, but still strong enough to takeknocks and to provide a physical barrier. Twomaterials which have been used widely in recenttimes are:

Paintings 119

Foam Cora composite consisting of outerlayers of paper and an inner layer ofpolystyrene; and

Corflutea synthetic corrugate.

pH-buffered, corrugated archival cardboard andother stable materials can also be used. Theabovementioned materials are considered to bemore chemically stable than timber or Masonite.

If you retain a timber or Masonite backing,introduce a barrier between it and the painting.The barrier could be acid-free paper or board.

Sometimes a work will have an original backingboard with inscriptions and labels. If this is thecase you will probably want to retain thisinformation. If the labels are in poor condition,you should consult a conservator regarding theirpreservation. All labels and inscriptions providepotentially valuable information about the work. Itis important to transcribe this information intoany records you keep about the painting, includingcondition reports.

Sometimes a backing board may hide informationon the canvas.

In some instances a conservator will transcribethis information onto the backing board, notingthat the original exists on the canvas.

If the back of the work has a large amount ofinformation or you want the information to bevisible, a sheet of Perspex can be used as thebacking board. In this way, the work is protectedwhile still allowing the back of the work to beviewed.

Backing boards are screwed into the back of theframe and should fit well enough to make a dustseal. They provide more protection from impact ifthey are attached to the framebecause theframe, rather than the painting, will absorb mostof the shock.

It is important to note that backing boards shouldnot be attached to the stretcher or strainer,because this weakens the structure and maynecessitate putting holes in the canvas, whichcould lead to tearing.

Glazing

Glazing is a generic term and usually refers toglass or Perspex.

When glazing, you should be ensure that:

there is sufficient space between the glass orPerspex and the surface of the work, so thatthe paint surface will not touch the glazing.Slips and spacers should be used to providethis space. Slips are visible and can be adecorative element in the frame. Spacers arenot seen;

Perspex is not used where there is any dangerof the paint or image layers being affected bystatic electricity, for example, where there isflaking paint or where there is mixed mediumsuch as in collage; and

you do not use glazing when framing workswhich have been recently varnished, becausethe varnish will not be able to dry properlyand may develop a white bloom.

There are a number of different types of glass onthe market, including very expensive, water-clearbullet-proof glass. If you want to use this glass,you should check with your State art gallery to seeif they have a local supplier, as this glass is notreadily available.

Back of framed painting showing Corflute backingboard screwed to the frame.

Photograph courtesy Artlab Australia

120 Paintings

Putting the painting in the frame

The following diagram shows how a stretchedcanvas painting should be fitted in a frame toprovide a protected environment for the painting.

The back of the frame is built up with a profilesection screwed to the frame. This increases thedepth of the rebate, and provides the recessedspace for the mirror clips and backing board.

The slip is necessary to ensure that the paintsurface does not contact the glass.

The slip, rebate and mirror platesthat is allsurfaces contacting the paintingneed to befelted with either a polyester felt or an inertcushioning material such as Cellair.

If the painting fits loosely in the frame, spacersshould be used to bulk out the rebate. Rag board,pH-buffered cardboard, balsa wood, cork and FoamCor are suitable materials. These spacers should beglued to the rebate to prevent them slipping outof place and so to reduce the risk of damage tothe painting.

Felted mirror plates are used to hold the paintingin the frame. These can be bent slightly to holdthe painting and are screwed into the profile.

Panel paintings should be held in place by twomirror plates placed at either side of the paintingin line with the grain of the wood. This meansthat, if necessary, there is some freedom ofmovement of the wood. Remember that if a panelis unable to move it will crack.

CAUTION:

You will find that many works are held in the frame with nails. Hammering nails into place

causes severe vibration which can lead to damage.Nails can also be difficult to remove without

damaging the tacking edge and the stretcher. If the nails pass through the stretcher, then the painting cannot be keyed out. When reframing these paintings, remove the nails and do not

replace them. Instead, use metal plates or mirror plates which can be screwed into place.

Hanging paintings securely

For safe hanging, paintings need to be secure intheir frames and each frame needs to be securelyhung from two points in the wall, with a hangingdevice attached to two points on the frame.

Paintings of different size and weight may requiredifferent hanging systems, but if you thinksensibly about the problems that may arise whenyou are hanging a particular work, most problemscan be averted.

There are two main principles to keep in mindwhen hanging a painting:

the work should be properly supported for itsweight; and

there should be no stresses on any part of thehanging system or the painting.

FrameGlazing

Slip

Paint and canvas

Stretcher

Felted mirror platescrewed to profile

Backing boardscrewed to profile

Stepped profile

Hanging systemscrewed to profile

Felted rebate

Rebate

Frame section (member)

Frame

Mirrorplate

Mirrorplate

Grain direction

Paintings 121

Some basic principles to keep in mind are:

Use materials which will not rust. Forexample, you should use nickel-plated screws,brass or nickel-plated screw eyes or D-rings,and non-rusting multi-strand wire if you areusing wire. If you use materials which rust,they will lose strength when they rust andyour paintings will be at risk.

Ensure that the wall into which the hangingsystem is secured is stable and structurallysound. If possible hang works from a wellsecured picture rail. If this is not available,make sure that you attach the plugs or securehooks with toggle bolts into the studs in thewall structure.

Ensure that stresses are evenly distributedacross the work. If the work is large, use ashelf to take the weight.

Do not hang the painting from one point,because this will create stress across the backof the frame, weakening corners and openingmitres. On an ornate frame this may result inloss of decoration.

For a light- to medium-sized framed painting:

the work should be hung from two separatepoints on the wall, with the hanging deviceattached to two points on the back of theframe;

the hanging devices should be strong enoughto take the weight of the work withoutbecoming stressed or warped; and

if you are using hanging wire, ensure that itis not crimped as this will be a weak point.

For hanging a heavy work:

use a shelf to evenly distribute the weightalong the bottom of the work, and use thehanging devices to secure the work againstthe wall; and

if necessary provide four or more hangingdevices, such as mirror plates screwed to theframe and then into secure sections of thewall.

Hanging devices

Hanging devices need to be strong and rust-proof.D-rings are preferable to screw eyes because theyare less likely to snap and are not weakened by thescrewing process.

Mirror plates are another secure method of hanging paintings.

OZ Clips are useful for large works with thinframes, particularly those which are kept intravelling frames.

There is also a range of security screws which canbe used when a painting requires protectionagainst theft.

Ideal conditions for thestorage and display of

paintings

As we have seen, paintings are made up of anumber of different materials. Each of thesematerials has its own particular sensitivity to thesurrounding environmental conditions. However,unless you are able to identify the exact materialsyou will not know their exact sensitivity. To assistmuseums, galleries and libraries in looking after

D-rings.

Photograph courtesy of Artlab Australia

Oz clips.

Photograph courtesy ofArtlab Australia

122 Paintings

their collections, guidelines for the ideal storageand display environments have been developed.

Ideally, paintings should be stored in anenvironment where:

Temperature is constant and moderatein therange 1820C.

If temperatures are generally outside this range inyour area, try to ensure that fluctuations are notrapid and are kept to a minimum.

Relative humidity is in the range 45-55%.

This is important for paintings, because most of theircomponents are moisture-sensitive and extremes ofrelative humidity can lead to physical damage.

Fluctuations in relative humidity should be kept toa minimum and should not be rapid. Fluctuationsin relative humidity can lead to severe distortionand to separation of the paint from underlyinglayers of the painting structure.

Light is kept to the minimum necessary for theactivity.

If possible, store paintings in the dark. If light isnot required for viewing while the works are beingstored, then there is no need for them to beilluminated. This will reduce the risk of fading anddiscolouration of particularly sensitive componentsof the painting.

For display it is necessary to have light; but thebrightness of the light should be less than 250 lux.

The UV content of the light should be no greaterthan 75w/lm and preferably below 30w/lm.

Steps are taken to protect paintings from dust andpollutants.

For more information

For more information about temperature, relative humidity, light and UV, please see Damage and Decay.

General storage and display guidelines

Careful consideration should be given to thestorage site and the storage system. In situationswhere you are able to achieve the ideal conditions,a good storage system in an appropriate storagesite will give added protection to your collection.If the available facilities or the local climate makeit difficult for you to achieve the ideal conditions,the selection of the storage site and themaintenance of a good storage system will becomeeven more critical in preventing damage to thecollections.

Wherever possible the storage and display sitesshould be in a central area of the building, wherethey are buffered from the extremes of climaticfluctuations which can be experienced nearexternal walls or in basements and attics.Basements should also be avoided because of therisk of flooding.

The storage site should not contain any water,drain or steam pipes, particularly at ceiling level.If these pipes were to leak, extensive damagecould result.

The storage and display sites should be reasonablywell ventilated. This will help reduce the risk ofinsect and mould infestation.

Inspect and clean storage and display areasregularly. Thorough and regular cleaning andvigilance will also greatly assist in the control ofinsects and mould.

Do not store paintings in sheds or directly on thefloor.

Cover stored paintings with a Tyvek cover. Theseare easy to make for individual works, using adomestic sewing machine. They will protect thepaintings and their frames from dust and insects.These covers will also help to protect the worksfrom fluctuations in environmental conditions.

Always give paintings adequate support and try toreduce the physical stresses which can cause damage.

If you have a number of paintings which are to bestored for considerable periods, consider designinga specific storage area so the paintings can be

Paintings 123

hung securely for storage. A heavy-gauge wire gridcan be used for this purpose. If consideringbuilding such a system, consult a conservator forfurther details.

If paintings are to be stored against walls, ensurethat they are placed on padded blocks to takethem off the floor level; and ensure that they arenot near heavy traffic areas, because they could bedamaged as people walk past them or if peopledrop things on them.

Design your display lighting so that the heatproduced by the lights does not affect thepaintings.

Heat associated with light can cause localised anddifferential environmental changes, andsubsequent dimensional changes across thepainting.

Always avoid direct sunlight on your paintings.

Storing unstretched paintings

Ideally, unstretched paintings should be storedflat. But many larger paintings are too large forflat storage in standard storage furniture. For thefull protection of these larger paintings, rolledstorage is recommended.

It is important to note that for the flat storage ofunstretched paintings, the paintings should bekept on wide, flat shelves or in large flat drawerssuch as plan chest drawers.

The shelves or drawers should be larger than thepaintings. This prevents distortion of the edges ofthe canvas.

Paintings can be stacked one on top of another,but paintings can be quite heavy and the ones onthe bottom have to carry the weight of those ontop. So be sure to limit the number of paintingsper stack.

Stacked paintings should be interleaved with thinProtecta Foam sandwiched between acid-freetissue.

If possible place the paintings in a large storagebox, 100150mm deep.

When rolling paintings for storage, it is importantto note that:

paintings must be rolled painted side out,otherwise permanent damage which mars theappearance of the work can result;

paintings should be properly interleaved andthe roller properly padded;

the roller should be as large as possible indiameterat least 200mm.

Rollers can be specially made of lightweightmaterials, such as:

Ribloc, with the ribs on the inside;

PVC pipe. A 300mm diameter pipe is a goodsize for most works;

if you are using a cardboard tube to roll apainting, pad it out to as large a diameter aspossible.

Rollers should be covered with a layer of padding-either polyethylene foam such as Plastazote orDacron wadding covered with clean, white cottonfabric-to compensate for any irregularities in thepaintings thickness.

It is best to roll the painting with an interleavinglayer of Tyvek, to prevent any transfer of pigment.The Tyvek should be larger in length and widththan the painting. When rolled, the paintingshould be tied firmly, but not tightly, with cottontape in several places along the roll.

If more than one painting is to be rolled on aroller, the paintings should be laid out flat andinterleaved with Protecta Foam, as for flat storage.Once this is done, the paintings should be rolledonto the roller, all at the same time. Remember, allthe paintings should be paint side out.

124 Paintings

Paintings in Australias climatic zones

The climatic zones outlined below are broad categories. Conditions may vary within these categories,depending on the state of repair of your building and whether the building is air conditioned or not.

Remember that the variations in environmental condition across Australia are extreme. Therefore, you shouldbe careful if you are transporting paintings from one climatic zone to anotherfor example, transportingworks from a warm moist tropical environment to an air-conditioned gallery. If works are travelling, ensurethere is enough time to acclimatise them on their arrival and return.

Arid

This climate is generally very dry, however in arid areas it is often very hot during the day and very coldat night. This wide fluctuation in temperature is matched by wide fluctuations in relative humidity, forexample from 75%20% in a day.

When caring for paintings in an arid climate it is important to note:

Many of the materials that make up paintings will tend to give out the water they containthis canlead to components of the paintings becoming dry and brittle;

The composite nature of paintings means that they are particularly susceptible to damage fromfluctuations in temperature and relative humidity. As the different materials release moisture at differentrates, warping, dimensional change and delamination of layers of the painting structure can result;

Remember that even arid areas can have periods of higher relative humidityeven though theperiods may only be very short. High humidities will cause swelling of some materials, and willincrease the likelihood of insect and mould attack;

Dust can be a major problem for paintings in an arid climate. It is important that paintings areglazed if dust is a problem; and

For particularly sensitive, reactive works you may consider placing RH buffered fabric or silica gelcells into the framing structure. You will need to discuss this with a conservator.

Note: If your collections of paintings have been kept in an arid environment for a considerable periodand they are stabledo not try to alter the environment to meet the recommended ideal conditions.This could do more harm than good. The emphasis should be on long term stability.

Summary of conditions for storage and displayStorage Display

Temperature 18C22C 18C22C

Relative Humidity 4555%RH 4555%RH

Brightness of the Light Dark storage preferred, but Should not be higherif light is present it should than 250 lux.not be higher than 250 lux.

UV Content of Light Dark storage is preferred but if No greater than 75 W/lm,light is present, UV content should preferably below 30W/lm.be and no greater than 75 W/lm and preferably below 30 W/lm.

Paintings 125

Temperature

A temperature climate is considered a moderate climate, however, temperate climates tend to have agreater range of temperatures than tropical climates and may include extreme climatic variations.

If you redecorating or designing storage and display areas, consider using materials that will help tobuffer these areas against rapid fluctuations and extremes or relative humidity and temperature. Thiswill help to reduce the risk of damage due to the fluctuations and extremes that occur in temperateenvironments.

Remember that many of Australias main cities and major regional centre are in temperate regions.These areas tend to be heavily polluted and this should be taken into account.

Salt laden winds and dust can be problems in many urban and rural areas in temperate zones.

Note: If your collections of paintings have been kept in a temperate environment for a considerableperiod and they are stabledo not try to alter the environment to meet the recommended idealconditions. This could do more harm than good. The emphasis should be on long term stability.

Tropical

These climates are characterised by heavy rainfall, high humidity and high temperatures.

When caring for paintings in tropical climates it is important to note that:

insects and moulds thrive and reproduce readily;

chemical deterioration reactions generally proceed faster at higher temperatures;

materials that have been in a tropical environment for some time will have a high moisture contentIf they are suddenly moved into a drier environment they are likely to suffer shrinkage and warpingof the support and stretcher;

many of the materials which make up paintings are very reactive to changes in relative humidity. Forexample the animal skin glue used as the size will soften; a wooden stretcher may warp, etc.; and

composite works such as collage will be particularly vulnerable.

Controlling moisture is important in a tropical environment.

Condensation may be a problem for glazed works and you may need to consider providing air holes inthe backing board to allow adequate air flow. Cover these air holes with gauze to prevent insect entry.

Ensure that your storage and display spaces have good air flow.

For particularly moisture sensitive works you may consider placing RH buffered fabric or silica gel cellswithin the frame. You will need to discuss this with a conservator.

Note: If your collections of paintings have been kept in a tropical environment for a considerable periodand they are stabledo not try to alter the environment to meet the recommended ideal conditions.This could do more harm than good. The emphasis should be on long term stability.

126 Paintings

MORE ABOUT PAINTINGS

Keying out

There are a number of problems which can arisewhen a work is keyed out. For this reason youshould never attempt to key out a work unless youhave been trained to do this properly by aconservator and you are aware of potentialproblems.

Older canvases can be extremely brittle and maytear at the corners, or elsewhere along the rolloveror tacking edge.

Some paintings which have been distorted over aperiod of time may have a very strong plasticmemory in their canvas or paint layers and keyingthem out may cause severe stress with crackingand even cleavage and flaking in the stressedareas.

You should carefully consider the strength of theadhesion on mixed-media works such as collage,which may delaminate with movement of the canvas.

What can go wrong with a stretcher and what

you can do

As the purpose of the stretcher is to ensure thatthe canvas is kept taut, it is obvious that astretcher which can no longer be keyed out is notperforming its function properly.

One of the most common reasons for a stretcher tofail is that the keys become damaged-with theprotruding end breaking off and the remainder ofthe key becoming lodged in the keyhole. Theremoval of the remnants of the key is usually a jobfor a conservator, because it involves separatingthe two stretcher members.

In some cases, a stretcher will not remain keyedout and keeps pulling back. If the reason for thisis not clearsuch as material caught in the keyholesyou should consult a conservator.

Sometimes stretchers warp and the temptation isto replace them. If, however, the canvas has takenon the plastic memory of the warped stretchershape, then replacing the warped member with astraight one may cause more problems than itsolves. If in doubt, consult a conservator.

Handling straps

When the work has no frame, handling straps madeof synthetic webbing can be screwed onto thebacks of frames or stretchers. These materials areavailable at marine or mountaineering suppliers.Handling straps provide added support for carryingwhen the frame is too weak or insubstantial to beused for carrying, or when there is no frame, or thework is particularly large and additional support isrequired.

Labels and inscriptions

The types of labels and inscriptions commonly foundon backing boards include framemakers labels, chalkmarks from auctioneers rooms, names and addresses,and other ancillary material. All this material shouldbe noted on the accessioning documentation andthe condition report as it can be critical when tryingto determine provenance, examine authenticity orsimply undertake historical studies.

If you have a problem related to the care,framing or hanging of paintings contact aconservator. Conservators can offer advice andpractical solutions.

For further reading

Clifford, T. 1983, The Historical Approach to theDisplay of Paintings, Journal of MuseumManagement and Curatorship, Vol. 1 (2),Butterworth Scientific Ltd, Guildford, UK, pp93106.

Editorial 1987, Journal of Museum Management andCuratorship, Frames and Framing in Museums,vol. 4, 1985, pp 115117; Vol 6, ButterworthScientific Ltd, Guildford, UK, pp. 227-228.

Paintings 127

Hackney, Stephen 1990, Framing for Conservationat the Tate Gallery, The Conservator, Number 14,The United Kingdom Institute for Conservation,London, pp4452.

Hasluck, Paul N. 1912, Mounting and FramingPictures, Cassell and Company Ltd, London.

Keck, Caroline K. 1965 reprinted 1980, A Handbookon the Care of Paintings, American Associationfor State and Local History, Nashville.

McTaggart, Peter and Ann 1984, Practical Gilding,Mac & Me Ltd, Welwyn, UK.

Payne, John and Chaloupka, Peter, 1986, Framingthe 9 x 5s, Bulletin of the Society of theNational Gallery of Victoria, The Society of TheNational Gallery of Victoria, Melbourne, pp1112.

Seager, Christopher; Hillary, Sarah L.; Weik, Sabine1986, Art Care. The Care of Art and MuseumCollections in New Zealand, Northern RegionalConservation Service, Auckland City Art Gallery,Auckland, N.Z.

National Gallery of Art 1991, Art in Transit: Studiesin the Transport of Paintings, National Gallery ofArt, Washington, DC.

Self-evaluation quiz

Question 1.

The support layer of a painting is:

a) the layer put on the back of the frame tosupport it;

b) the framework that supports the canvas;

c) the rigid board used to support unstretchedpaintings when they are being carried; or

d) the layer which carries or supports the imageor paint layer.

Question 2.

Which of the following statements are true?

a) Traditionally paintings were produced onstretched canvasses or wooden panels.

b) There is no difference between a stretcherand a strainer.

c) The varnish layer serves only to make thepainting look glossy.

d) A stretcher differs from a strainer in that thecorners of a stretcher can be keyed out totighten the canvas.

e) Paintings can be produced on a range ofsupports.

Question 3.

Fluctuations in relative humidity can damagepaintings by:

a) producing dimensional changes in thesupport, which can lead to separation of theimage layer from the support;

b) producing dimensional changes in thesupport, which can lead to cracking of thepaint and varnish layers;

c) warping the stretcher, which in turn producesdistortion of the canvas support;

d) increasing the risk of mould attack when therelative humidity is high; or

e) All of the above.

Question 4.

Which of the following statements are false?

When handling paintings you should:

a) Be sure the painting and frame are secure andsafe to move.

b) Put your hand around the stretcher bar withyour fingers between the stretcher and thecanvas. This allows you to get a good grip.

128 Paintings

c) Check your route and make sure it is clear.Also make sure all doors are open and thatthere are people available to assist if youneed them.

d) Carry more than one painting at a time.

e) Carry wrapped paint i ngs with ex t ra care,because you cannot see what you are touc h i ng .

Question 5.

A good protective framing system will:

a) Protect a painting from knocks, because theframe will take the force of the impact.

b) Include a backing board, to protect the backof the painting from impact damage and tosignificantly reduce the risk of insect attackand dust build-up.

c) Be designed with protection, the history ofthe painting and aesthetics all taken intoaccount.

d) Have a slip or a spacer to keep the glazingaway from he paint surface.

e) All of the above.

Question 6.

W hen putting a paint i ng into its fra me, you sho u l d :

a) Use hammer and nails to fix the painting inplace as this is difficult for people to undoand will ensure that it wont come loose.

b) Ensure that all surfaces contacting thepainting eg. the slip, the rebate, the fixingsetc are cushioned with an inert cushioningmaterial.

c) Use spacers between the painting and theframe, if the painting fits loosely in theframe.

d) Build up the back of the frame with astepped profile section to accommodate thebacking board, the painting and the glazingand slip, if the frame includes glazing.

Question 7.

Which of the following statements are true?

a) Paintings should be hung securely becausethey can be badly damaged if they fall off thewall.

b) Paintings should be hung from two points onthe wall.

c) The hanging devices should be strong enoughto take the weight of the work withoutbecoming stressed or warped.

d) The hanging device should be attached totwo points on the frame.

e) If the work is exceptionally heavy, additionalsupport can be given by resting the base ofthe frame on a shelf.

Question 8.

What are the ideal conditions for storing anddisplaying paintings?

a) 18-22C, 5570% RH, brightness of the lightat 550 lux and the UV content of the light nogreater than 75W/lm and preferably below30W/lm.

b) 20-30C, 4555% RH, brightness of the lightat no more than 250 lux and the UV c o nt e ntof the lig ht no greater than 200W/lm andpreferably below 100W/lm.

c) 18-22C, 4555% RH, brightness of the lightat no more than 250 lux and the UV c o nt e ntof the lig ht no greater than 75W/lm andpreferably below 30W/lm.

d) None of the above.

Question 9.

When storing paintings, you should:

a) Ensure that they have adequate support.

b) Place them on padded blocks on the floor, inan area where people are likely to walk pastthem often so that they can check theircondition regularly.

Paintings 129

c) Protect them from dust and fluctuations inrelative humidity.

d) Roll large, unstretched paintings if you donot have storage furniture which canaccommodate them flat.

Answers to self-evaluation quiz

Question 1.

Answer: d).

Question 2.

Answer: a), d) and e) are true. b) is false. There isa difference between a stretcher and a strainer. Astretcher can be keyed out to tighten the canvas,whereas a strainer cannot. c) is false. The varnishlayer protects the paint layer and gives the paintcolours a richer appearance.

Question 3.

Answer: e).

Question 4.

Answer: b) and d) are false.

Question 5.

Answer: e).

Question 6.

Answer: b), c) and d) are correct. a) is incorrect.Nails should not be used to fix paintings into aframe, because hammering them in causesvibration which could lead to considerable damage.

Question 7.

Answer: a), b), c), d) and e) are all true.

Question 8.

Answer: c).

Question 9.

Answer: a), c) and d). b) is not correct. Ifpaintings are to be stored against walls, youshould ensure that they are placed on paddedblocks to take them off the floor level, and ensurethat they are not near heavy traffic areas, becausethey could be damaged as people walk past themor if people drop things on them.

Given the well established catalogue of drawbacks it is perhaps surprising that more attention has not been paid to developing new supports. One of the reasons for this is that the conservators have not really played a very prominent role in the development of new materials for artists. This is short sighted. We have tended to see ourselves as a group who acts on old works after the event of creation in order to try and slow down their inevitable deterioration. But we should also be prepared to extend our role so that we can try to advise living artists as to the best materials before they commence work. Such an approach is probably essential if the sheer volume of art created today is to have much chance of survival. Of course it may be objected that many artists do not care whether their work survives. If that is so then they have the right to make that choice. The problem at the moment is that artists are not able to obtain readily information as to the durability of their materials. Such information is not widely enough available in art schools or in literature likely to be consulted by artists.

Linen and cotton have continued to be preferred by artists seeking to paint on stretched fabrics. Given the materials previously available, linen in particular has always been a sensible choice, yet today from the viewpoints of their chemical stability and mechanical properties they are very far from ideal materials. It is worth considering some of their drawbacks in more detail since this will help to serve as one reference point in assessing new materials.

Strength loss is the most evident problem. Whilst linen and cotton begin their life with much greater strength than is necessary for a painting support, they retain it only for a short period. The cellulose chains of which they are composed suffer degradation leading to chain scission under the influence of light, moisture and environmental pollutants. The strength loss is rapid and extensive. Tests conducted on samples naturally aged in the Tate Gallery London revealed that in only 24 years linen canvas samples had declined to practically 1/3 of their original strength. Hardly surprising then that so few canvas paintings survive more than a couple of hundred years without some form of treatment to provide additional structural support. Unlined paintings of more than 300 years of age are so rare as to be almost collectors items. Some of this extensive treatment must of course be attributed to lining having become a standard restoration treatment, though it should be remembered that this is not without a certain basis in the condition of the paintings themselves. It is evident that a large number of 20th century paintings have already been lined after perhaps only 50 years of existence. Such treatments are themselves hazardous operations and tend to impose significant changes on the appearance and handling properties of the painting especially if considered as a whole object rather than simply the visual image.

Cotton is even less satisfactory than linen. The fibres are 2 to 3 times weaker than equivalent linen fibres and consequently though their rate of deterioration due to light is slower than that of linen, low strength values will quickly be reached. These factors are sure to cause immense problems for conservators fifty years from now entrusted with the care of the large paintings on cotton which are so common in our galleries today.

Just as problematical given the optical role that exposed canvas plays in many modern paintings are the colour changes that accompany thechemical degradation. Significant darkening and yellowing of the surface take place very rapidly. The 24 year old linen samples from the Tate Gallery showed a decrease in reflectance of 10% at the red end of the spectrum and 50% at the blue end of the spectrum.

Again cotton is known to change colour more rapidly than linen and since its natural cream white colour has often been utilised by artists such a change will completely alter the tonal relationships within the painting. The original intention of an artist such as Morris Louis or Helen Frankenthaler will be irretrievably lost.

But more subtle problems also exist. Linen and cotton are moisture sensitive supports. The moisture regain at 65% HF of linen and cotton is taken as 12% and 8.5% respectively. They swell and shrink differentially from other layers in the painting and their mechanical properties also change. This process in the painting as a whole can lead to powerful shear and tensile stresses being set up and to cracking and delamination. Cotton can imbibe as much as 40% moisture at 100% RH and appears to respond more rapidly to moisture changes. It has been observed that large paintings on cotton are particularly prone to fluctuations between very slack and very taut states. This affinity for moisture also leads to soiling of the cotton and linen supports

MECHANICAL PROPERTIESWoven fabrics in general and cotton and linen in particular do not have ideal mechanical properties when considered for use as a painting support. What is required is a material which becomes taut under the minimum of applied strain, which does not subsequently relax and which has the same properties in all directions. This requires a material of high initial Youngs Modulus (and low elongation) resistant to stress relaxation and creep and exhibiting isotropic behaviour. Cotton and linen fail on all these counts when considered in the woven form.

They require considerable amounts of strain (from the point of view of the paint ground and size layers) to achieve a taut state. What is more they do not follow a classical Hookean stress/strain extension curve, but

EXCERPTS FROM ARTISTS CANVASES: THEIR HISTORY AND FUTURE

stretch first by the removal of the crimp in the weave. This initial low modulus extension is hardly reversible and hence rapid stress relaxation follows. So if canvas is to remain taut for any length of time it must be pre-stretched before it is painted on. This drawback exists depending on weave type to a greater or lesser degree with all woven fabrics including glass fabrics. However even once the decrimping region is passed the cotton or linen canvas will not retain its taut state over a prolonged period of time. This is because under constant applied strain they suffer from stress relaxation. So a canvas which was initially tightly stretched can become slack over a number of years. To counter this effect since the eighteenth century stretchers have been made with wedges enabling them to be regularly enlarged to re-tighten slackened supports. Unfortunately doing this causes the renewed application of very high stresses at the turned over edges of the painting and the corners. Since the linen or cotton will by this time have also declined in strength the frequent result is fracture of the canvas starting usually at the top edge and corners.

On large paintings such problems are further magnified by the weight of canvas involved. This can be so great that it causes the canvas near the top of the painting to gradually extend (creep) under the constant applied load of the canvas lower down. Creep which has been studied by Tassinari in relation to hemp canvas is the other side of the coin of stress relaxation and can lead to bulging along the lower edge of paintings. Again the treatment is often wedging out which brings the eventual failure at the edges one step nearer.

Whilst stress relaxation, creep and Youngs Modulus can all be improved upon by the judicious choice of materials the anisotropic nature of canvas stems mostly from its woven character. Woven materials tend to be highly anisotropic. Their two stiffest directions are the weft and warp but it is common for the weft in the initial phases of stretching to be two or three times stiffer than the warp. Appropriate choice of weave can minimise this difference, but the problem will still exist. It is no doubt more serious in cotton and linen which respond to moisture and thus must also transmit anisotropic strains to the paint and ground layers.

This leads us to the fact that canvas paintings are secured on stretchers. The stretcher serves to restrain the painting from contracting back to its unstressed size while it remains elastically deformed. Complex strain patterns are generated throughout the layers of the painting which tend towards maxima at the edges and corners and reduce and become more uniform in the central zone. Further shrinkage of the painting whether caused by desiccation of a size layer or by moisture content in the canvas will superimpose higher stresses onto the pattern imposed by the restraint of the stretcher, cracks and delamination can then result.

Cotton and linen interact with this fundamental problem of restraint on a stretcher in three ways.

First because they are not high Modulus materials in the woven state stretching them to a taut state requires relatively large applied strains. There is thus in the painting composite always a danger that large strains may need to be imposed on the paint and ground layers in order to tighten the whole structure. This will obviously be influenced by factors such as the thickness and degree of cracking of the paint and ground layers.

Second cotton and linen respond to moisture changes, they thus contribute to either very dramatic additional stresses such as when they become extremely moist or else much more gradual but repetitive stress changes as the humidity fluctuates. These cyclical changes may well lead to failure in the paint layer due to fatigue mechanisms, but this requires further investigation.

Thirdly their creep and stress relaxation behaviour outlined above mean that the stretching process is not a once for all procedure, but one which of necessity if the painting is to be kept taut must be repeated frequently in the life of the painting.

These points emphasise that it would be short sighted to consider the fabric support as the only problem. Evidently the whole stretching process must be called into question and the design of stretchers more carefully considered. In recent years for instance there have merged spring tensioned stretchers which rely on mechanical systems to expand and contract the overall dimensions. These do at least allow the possibility of some retraction, i.e. reduction in restraint which may be a definite advantage. On the other hand they tend to maintain high tension states and do not change the nature of the basic imposed stress system. It is perhaps indicative of a growing concern amongst artists for their materials that Richard Hamilton has designed, patented and had manufactured a number of mechanical stretchers for his own use.

Amongst other causes of problems Marion Mecklenberg has pointed out that it would appear that one of the most active layers in the painting composite appears to be the glue size layer. He suggests that desiccation can lead to very large stresses in the size film which can lead to fracture in the paint and ground layers. This would strongly imply that a new artists canvas should avoid the need for moisture responsive size layers. Cotton and linen are traditionally associated with the use of size. Not only are they frequently sized by the artist, but they are often sized at least on the warp threads during weaving.

Two reasons are commonly cited for the sizing of canvas by artists. One is that it is necessary to prevent cellulosic materials from coming into contact with oil paint. This need is of course specific to cotton and linen fabric although it is worth noting that there is very little

evidence available to quantify the effects of such contact. The other is that the ground layer needs to be prevented from penetrating through to the back of the canvas. This problem would continue to exist with modern alternative fabrics and emphasises that not only do we need to find a material which does not require sizing with animal glue, but that this must be related to suggestions as to the most suitable types of ground. In this area synthetic materials particularly acrylics are already being widely used.

Finally it is worth noting that cotton and linen are both susceptible to mould growth and deteriorate even more rapidly if they have the misfortune to be in very damp conditions. Several artists have already expressed specific concern about this problem particularly with paintings in acrylic media on cotton duck.

The need exists then for an investigation into fabric supports. It is necessary at the start to list some of the desired parameters of a suitable fabric:-

1 excellent durability, resistance to acidic pollutants and light.

2 high stiffness (Youngs Modulus), low extensibility.3 good elastic recovery.

4 negligible hygroscopicity (moisture pick up).5 resistances to creep and stress relaxation.

6 good adhesion to chosen grounds.

7 lack of need for sizing.

8 acceptability to artists (texture, handling, appearance, etc).

9 low cost, ready availability, large sizes.

Acrylic fibres tend to have lower tenacities than do flax and cotton as well as quite high elongations and this latter is undoubtedly the major drawback. It makes them highly flexible and also pleasant to handle, hence their use in clothing. Their chemical stability is excellent. For instance Orlon acrylic type 42 will withstand 1000 hours in 60% concentrated sulphuric acid; by comparison cotton degrades in less than 10 hours under the same conditions. Light resistance is also extremely good; acrylics tend to have the best resistance to ultraviolet radiation in daylight. These properties of flexibility and stability have resulted in acrylics finding use as media, varnish and adhesives in the painting and conservation field. Certainly their compatibility with an acrylic support would be outstanding. On the other hand the ideal combination in a painting would be a stiff dimensionally stable support with a permanently flexible ground and paint layer and acrylics may well not provide this support stiffness. They do also absorb some moisture having regain values of 1-2.5% but this is fairly small.

Polyester fabrics would appear to be the most satisfactory synthetics which are readily available. The fibres have high tenacity and relatively low elongation at break, they are thus fairly stiff. Elastic recovery though worse than nylon is better than polypropylene. They will also withstand 3% strain without any permanent set occurring. Moisture absorption is extremely low, typically around 0.4% at 65% RH and the fibres will imbibe only 2% moisture when maintained at 100% RH. At low extensions the fibres resist creep and they are characterised by a fairly high initial modulus of 100-130 gm/denier. Polyesters have good abrasion resistance, and are absolutely resistant to mildew and have good resistance to degradation by sunlight though this degradation is very significantly reduced if the ultraviolet component is excluded by glass. Indeed under this type of exposure certain polyesters can be superior to acrylics. The material is available in a wide range of forms, including spun forms which have fluffy canvas like appearance, it is also relatively cheap.

In developing new materials for the artist to use it would therefore seem at present best to focus attention primarily upon the polyesters and acrylics.

(ARTISTS CANVASES: THEIR HISTORY AND FUTURE)

C Villers, Courtauld Institute of Art, London

G Hedley, Courtauld Institute of Art, London

V Mehra, Central Research Laboratory, Amsterdam July 1980

Ottawa Symposium on Conservation of Contemporary Art National Gallery Canada) July 1980

Aluminum Honeycomb Supports: Their Fabrication and Use in PaintingConservation

Marion F. Mecklenburg; Judith E. Webster

Studies in Conservation, Vol. 22, No. 4. (Nov., 1977), pp. 177-189.

Stable URL:http://links.jstor.org/sici?sici=0039-3630%28197711%2922%3A4%3C177%3AAHSTFA%3E2.0.CO%3B2-N

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http://www.jstor.orgTue Apr 1 18:44:40 2008

Studies in Conservation, 22 ( 1 977), 177-1 89

ALUMINUM HONEYCOMB SUPPORTS: T H E I R

FABRICATION AND USE I N PAINTING

CONSERVATION

M A R I O N F . M E C K L E N B U R G and J U D I T H E . WEBSTER

Abstract-The fabrication and use of aluminum honeycomb core solid support panels for paintings on fabric are described, using standard materials and laboratory equipment. Tech- niques of mounting paintings to such all-aluminum solid supports employing the vacuum hot table and both wax/resin and thermoplastic adhesives are discussed. Alternative methods of panel fabrication and technical information on current materials are noted.

1. INTRODUCTION

For some time it has been apparent that the traditional method of consolidation, or lining, of a painting on fabric by bonding it to an auxiliary fabric support does not provide a satisfactory result in every case. It has been observed that torn paintings with marked distortion at the periphery of the damage, when lined on fabric, have an unfortunate tendency to revert to the original distortion, forcing the new fabric support out of plane and into conformation. In the case of oversize paintings, the combined weight of the original tensioned fabric, ground and design layers is an inherent weakness leading to eventual bond failure and cleavage of the ground and paint layers. The presumption is that this is due to compression when humidity oscillations have deprived the fabric support of its ability to maintain the structure in plane. The traditional lining, employing additional fabric and adhesive, adds to the weight and compounds the problem. In addition to problems presented by physical deterioration, of increasing concern to conservators are problems arising from the transportation and exhibition of paintings. Mr George Stout has discussed these problems specifically in regard to vandalism, rapid vibration or oscillation of fabric supports during shipping, and environmental changes in humidity and temperature during such moves [I] . Many painting conservators today believe that a solid support provides a reasonable solu- tion to these specific consolidation problems. Two recent papers have described the con- struction of rigid panels of end-grain balsa wood core and birch veneer plywood skins as supports for paintings with severe distortion [2, 31. As early as 1957, Stefan Slabczynski, then Chief Restorer at the Tate Gallery, London, built a panel with a kraft paper honeycomb core and masonite skins as a support for a painting by William Blake with severe cleavage problems. Honeycomb panels of this type are currently manufactured by Lebrun of New York. In 1971 Alexander Dunluce, Mr Slabczynski's successor, mounted a large painting by R. Delaunay on a honeycomb panel using paper core with fiberglas sheet and PVA as an adhesive. Subsequently he marouflaged a painting by Picasso to a panel constructed of paper core, 2 mm fiberglas sheets with a wax/resin adhesive and mulberry tissue interleave. Experimentation with solid support systems is continuing [4, 51. This early use of honeycomb panels constructed at the Tate was influential to our undertaking similar experiments. If, then, a solid support can provide a solution to specific problems encountered in con- solidation, what performance standards should be required? Certainly, the following:

2 * 1 - Long term durability and stability. A panel must remain stable in most environments

178 Marion F. Mecklenburg and Judith E. Webster

and be chemically inert. 2 - Sufficient rigidity to perform the task required. 3 - Resistance to surface deformation. 4 - Ease of construction, including the potential for the fabrication of large panels. 5 - Light weight. 6 - Ease in use. A panel must be compatible with currently accepted adhesives and lining

procedures, and meet requirements for reversibility. It is the choice of materials which ultimately governs panel behavior in a given environment. There are many possible structural combinations. Major differences occur in the materials used for fabrication, as is evidenced by the papers presented over the last few years des- cribing various methods. A painting's environment, including such factors as relative humidity, temperature, and airborne contaminants, is a primary concern in the preservation of paintings. Airborne contaminants can be filtered and relatively stable temperatures can be achieved. Relative humidity, however, is difficult to stabilize. A material impervious to moisture variation, yet stable enough through a controlled range of temperature variation, is essential. Aluminum fulfills these requirements and, unlike natural materials, has known uniform physical properties which permit the analytic determination of structures. An all-aluminum structure has performance characteristics that can be predicted. In the spring of 1974 the Washington Conservation Studio undertook the restoration of a major painting owned by the US National Park Service. The painting, The Grand Canyon of the Yellowstone by Thomas Moran, measures 144 x 84 in. Upon examination, it was evident that there was extensive compression cleavage due to the relatively thick ground and design layers, the failure of the upper tacking edge of the support fabric, and the considerable weight of the combined fabric and design layer. The pattern of this com- pression cleavage has since been observed with some frequency on other very large oil paintings on canvas. If the painting were to be consolidated and relined using conventional adhesives and new fabric support, only a temporary stay of deterioration would be achieved. The tension required to maintain a painting of this scale in plane would be enormous, requiring great fabric strength and heavy stretcher construction. The added weight would inevitably lead to the eventual repetition of the failure. If, however, a solid support were used, no tension to either the support fabric, ground, or design layer would be required. The bonding adhesive need only be adequate to hold the painting in contact with the panel surface while the panel would provide all necessary structural integrity and in-plane continuity. A bonded aluminum honeycomb core panel offered a possible solution. In consultation with Mr Ned Miller of the Hexcel Corporation, structural performance requirements were defined and the fabricated results were as follows:* 1 - Dimensions 144 x 84 in., with deflection under panel weight no more than 2 in. out of

plane in long direction. 2 - 15 mil skins 5052 aluminum alloy. 3 - 8 in thick aluminum perforated cell. 4 - Narmco adhesive. 5 - Surround adhesive Hexcel HP 326. 6 - $ in birch edge finish. 7 -Weight 77 lb. The final fabrication of the panel was performed by Hexcel. It is not the purpose of the paper to discuss the restoration of the Thomas Moran painting, but rather to illustrate that the problems presented in its consolidation indicated the need *Since these panels were constructed from commercially available materials, the standard US (non-metric) measurements have been retained throughout.

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179 Aluminum honeycomb supports: their fabrication and use in painting conservation

for a specific solution. The panel was totally successful-strong, lightweight, and easy to manipulate during the lining process. The all-aluminum structure allowed rapid heat transfer from the hot table to the top of the panel, permitting the painting to be lined 'face up' and eliminating the need for any application of additional heat to the surface of the painting. In effect, the lining technique was identical with the normal 'face up' procedure. While the panel for the Moran was fabricated specifically for that painting by a commercial firm with large industrial capacity, the question still remained whether a conservator could build and use such panels in his or her own studio in a reasonable time and at a reasonable cost. The design criteria and methods for fabrication and use developed by the Washington Conservation Studio outlined below indicate that the basic industrial process can be duplicated in a modern conservation laboratory.

2. DESIGN

The physical properties of aluminum are well defined and readily allow the determination of the structure necessary to support a particular work of art. In theory, support panels of a desired stiffness for small paintings would be quite thin. In practice, however, it was felt that a standard design suitable for use with a wide range of painting sizes would be more practical, as it would limit the number of materials to be stocked and simplify assembly. The design chosen is, in fact, stronger than necessary for panels under 8 ft in the larger dimension; it would suffice for panels up to 16 ft long. Although a reasonably lightweight panel was desirable, weight was not a prime consideration--ease of construction and handling were more important. The material components of the design ultimately chosen are as follows: 1 - Aluminum core-Hexcel ACG, & in cell, & in thick, perforated. 2 - Aluminum core-Hexcel ACG, & in cell, 3 in thick, perforated (for internal splices). 3 - Aluminum skin-Reynolds Aluminum 25 mi1 (0.025 in) sheet (3003 H 14 alloy). 4 - Adhesive-Hexcelite HP 326 (two part epoxy). 5 -Wood edging strips milled to & in, straight grained. 6 - Assembled weight-1.2 lb/ft2. Considering panel thickness first, the materials specified above will fabricate to approxi- mately Q in. This dimension is sufficient to allow the tackover edges of the original support fabric to be adhered to the panel edges. As the aluminum honeycomb core is assembled with a surround of wood stripping which is finished flush with the top and bottom skins of the panel, these edges can readily receive staples or screws if desired. In addition, the dimension chosen (Q in) lends itself to the splicing technique used to build panels over 4 ft in the shorter dimension. The aluminum skins could have been 20 mil instead of 25 mil. However, when handling sheets of aluminum this thin, it is easy to distort the surface and cause a dent. Twenty-five mil aluminum is somewhat easier to handle and proportionately more resistant to defor- mation. The core (ACG & in cell) is used for various reasons. First, the small cell size provides a sufficient bonding area to withstand certain thermal transitions during use on the hot table where painting attachment occurs. Second, the cell density provides a more continuous platform for the aluminum skin and eliminates the possibility of a skin surface texture caused by the cell. Third, the aluminum density of the core provides uniform heat trans- ference from the hot table to the painting during the attachment process. Fourth, the core cuts easily, since there is an inherent stiffness, and provides the opportunity to use small pieces in the construction of the panel, thereby eliminating waste. The adhesive, HP 326, is a thixotropic epoxy paste chosen for its strength and ease of manipulation. It takes heat well and is able to bond materials of different physical proper-

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180 Marion F. Mecklenburg and Judith E. Webster

ties. This is important as panels are normally finished with wood edging strips. It is evident that lighter weight material could be used with success, e.g. the original panel for the Moran. However, more care would be needed in the storage and handling of the materials as well as in the fabrication of the panel. Since painting size varies so greatly, it seemed wise to establish a standard design for panel construction employing materials and methods acceptable to the average conservation laboratory.

3. CONSTRUCTION

3.1. Panels Having at Least One Dimension Under 48 in

Step 1. Cutting the Aluminum Skins Four dimensions are required: height, width, and the two diagonals. The diagonal measure- ments should always be taken since it is so often found that paintings are out of square. Panels can easily be constructed to fit the painting exactly and it makes little sense to do otherwise. The dimensions are scribed on the aluminum sheet using a sharp steel point. A sharp point is necessary; otherwise, a 'strain-hardening' occurs in the aluminum after the first pass, making further scoring quite difficult. Three small indentations are made along a cutting edge and visually aligned to ensure that the measurements scribed are accurate. The actual cutting of the aluminum sheet is done as if one were cutting glass. A fairly deep trough is scribed by making several passes with the steel point. The sheet is then folded over a straight table edge with a fairly brisk motion, this right angle is continued to 180". reversed, and usually breaks on the second fold. This method of cutting does not distort the edges and is preferable to using shears or saws.

Step 2. Preparation of Wood Edging Redwood edging is used as it is fairly stable and easily worked. Strips &in wide are pre-cut from a standard 1 x 6 in redwood board. It is important that the &in depth of the strip be as accurate as possible because the strips must be flush with the core to eliminate any possibility of distortion of the panel surface. The surround of wood edging is a fraction larger than the aluminum skins because it is desirable to provide an excess which will be trimmed away when finishing the panel edges. While the corners can be mitred, it is not necessary. The corners are temporarily secured with brads set so that they can easily be removed later. The frame of wood strips is then taped to one of the aluminum skins and provides the guide for cutting and fitting the core.

Step 3. Fitting the Core The aluminum core is worked easily if some care is used. Place a sheet of core over the assembly of wood frame and single aluminum skin, mark the inside edge of the wood strips on the core with masking tape allowing an excess of + in all around. Place the core on a flat surface and, using a straight edge, cut the core with a sharp knife (a serrated kitchen knife works well), making several passes with moderate pressure. The core should now be about B-t in larger than the inside dimensions of the wood edging. Gently pass your finger over the edges of the core and press the excess to the proper dimension so that the core fits snugly inside the wood frame. It is not necessary that the core be a single, continuous piece. It can be several pieces, but there should be no gaps between core pieces larger than the cell dimension of t in. Step 4. Bonding the Panel Hexcelite HP 326 is a two-part thixotropic epoxy adhesive which has a four-hour pot life

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181 Aluminum honeycomb supports: their fabrication and use in painting conservation

at room temperature. The long pot life allows the adhesive to be mixed after cutting the pieces of the panel and still leave ample time for assembly. Excess mixed adhesive may be stored in a refrigerator for even longer life. Usually aluminum sheets are provided with a thin coating of oil to preserve the surface finish. As this oil film can reduce bonding strength, it must be removed by washing with a solution of water and 'sudsy ammonia' or detergent, and dried. The pane