benjamin powell smokehouse - colonial williamsburg...benjamin powell smokehouse treatment report...

BENJAMIN POWELL SMOKEHOUSE

May 2002

CONSERVATION TREATMENT REPORT

Thomas H. Taylor, Jr., Ph.D., FAIC, FAPTChief Architectural Conservator

Office of Architectural Collections Management

Cynthia D. JaworskiPreservation Technician

May 2002

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Acknowledgements

Michael P. Schuller

Wayne T. Ruth

Richard A. Livingston

Greg R. Kingsley

Jim L. Noland

Larry Evans

A. Elena Charola

Bryan Blundell

Roberta Laynor

Patricia Samford

Romeo Thomas

Connie Torrain

Dana Davis

Reinhard Sunnus

Carlos Corbett

Wayne Kille

Lindsay Hannah

John Hinchman

Lanna Ackers

Laura Martinsen

The authors would like to thank everyone who helped with theBenjamin Powell smokehouse conservation treatment process, especially

Content

Executive Summary 1

Architectural History 2

Description of Structure 4

Condition of the Architectural Features 5

Investigations 8

Conservation Objective & Treatment Methodology 12

Treatment Procedures 13

Results & Assessments 17

Project Statistics 18

Selected References 19

Appendix A 21

Appendix B 26

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Benjamin Powell Smokehouse Treatment Report

Executive SummaryThe Benjamin Powell House complex opened to the public in 1972. Interpretive objectives of the

site include telling the story of the Powell family, the daily and seasonal rhythm of the family’s domesticlife, and their connections to the rest of the community in the year 1774. The site, a favorite of schoolgroups, is visited by over 70,000 people each year. The complex’s smokehouse, the only survivingeighteenth-century brick smokehouse in the Colonial Williamsburg Historic Area, is an integral part of thedomestic scene.

The conservation treatment to stabilize the original brick walls of the Benjamin Powell Smokehousebegan on November 13, 2000 after nearly twenty-two years of monitoring, research, and analysis directedby Tom Taylor, Chief Architectural Conservator for Colonial Williamsburg Foundation. The treatmentlasted 180 days and was followed by a year of additional monitoring and analysis. All indications point toa successful treatment and attainment of conservation objectives. The following report documents theentire project and concludes with an assessment of the treatment and a set of recommendations forimproved treatment procedures.

It appears that the smokehouse began to deteriorate soon after construction and the degradation ofthe walls may have been the reason for the application of a cementitious stucco in the 1820s. Removal ofthe stucco during the 1955-56 restoration of the building added to the deterioration. Since 1980, morethan four centimeters of material have eroded from the surfaces of the walls as a result of salt crystallizationinside the brick pores. In addition, much of the rubble that filled the wall cavities leached out of the wallcreating voids and unstable conditions between the inner and outer wythes of brick. Large cracks formedin the interior surfaces and sections of the outer wall began to bulge.

The source of the salt that caused the deterioration of the bricks has never been identified. Analysisof the soil and the building materials indicates that salt did not come from the soil by way of rising dampas was first thought. Analysis also indicates that the salt could not have come from either the materialsused to make the brick and mortar or used to cure the meat. Instead, the salt appears to have come fromrubble that was used to fill the wall cavities either during construction or the rebuilding campaign thatresulted in the change from a pyramidal to a gable roof and the addition of stucco coating.

Treatment objectives were established to stabilize the walls through the injection of a lime-basedgrout and the desalinization of the brick units through poulticing. Although injection grouting and masonrypoulticing have long been used in architectural conservation, their application to the smokehouse wasunique. A specially formulated lime-based grout, compatible with the sand-lime mortar and soft hand-molded brick, was carefully injected into the wall cavities through 954 holes drilled into the mortar jointson the interior and exterior surfaces of the walls. Overall, 210 gallons of grout were injected into the wallcavities. Even before the grout began to set, a toilet-paper based poultice was applied to the interiorsurfaces of the smokehouse. Nearly five thousand rolls of toilet paper were used in seven separateapplications. Analysis of poultice samples indicated that a total of 38 pounds of salt were removed.Although we were not able to remove all the salt in the masonry, we removed enough to significantlyreduce the rate of deterioration of the brick surfaces by subflorescence.

While literature is sparse on desalinization of masonry by poulticing, we believe that this is thefirst time that toilet paper has been used as a poulticing material on an entire structure. The toilet paperpoultice was inexpensive, easy to mix and apply, and easy to remove. Unlike clay poultices, it did notleave a residue on the brick surface. Although more testing is needed, the toilet paper poultice has greatpotential for use in architectural conservation.

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Architectural HistoryThe Benjamin Powell Smokehouse is a post-1779 building according to archaeological evidence.

It does not appear on the Frenchman’s Map of 1782, a plan of Williamsburg that depicted most of thestructures, including outbuildings. Insurance records indicate the smokehouse was constructed between1793 and 1820, when Benjamin Carter Waller owned the property. The smokehouse, now named for thefirst recorded owner of the property, is part of the Benjamin Powell complex, which features a house,garden and several outbuildings, including a dairy of the same age, size, and construction as the smokehouse.

During the second quarter of the nineteenth century, the smokehouse was heavily modified, includingthe addition of a new gable roof and a stucco coating scored to look like stone. Since the dairy did notreceive a stucco coating, we believe the stucco on the smokehouse was intended to cover up the deterioratedbrickwork. If this hypothesis is correct, the building may have begun to deteriorate as soon as it was built,or was in a ruinous state prior to the nineteenth century alterations.

An aerial view of the Benjamin Powell complex during the treatment process. Note the plastic enclosurearound the smokehouse. The dairy, hidden in this picture by a tree, is located 37 feet to the left.

N

Dairy Smokehouse

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Colonial Williamsburg restored the smokehouse in 1955-56 to its original appearance based to alarge extent on the assumption that the smokehouse and dairy had similar roof configurations. The gableroof and brick gable ends were removed, a new door, doorsill, doorframe and brick lintel were constructed,and the floor was raised approximately one foot. Severely deteriorated bricks were replaced, especiallyaround the door, vents, and roof eaves. At the same time, the stucco coating was carefully removed usinghand tools such as scrapers and chisels, instead of using chemicals or air-abrasive equipment.

Southwest view of the smokehouse before the 1955-56restoration. Note the gable roof and stucco coating.

The west view during the 1955-56 restoration.Note the prevalent brick deterioration.

Partially obstructed east view of the smokehouse beforethe restoration

Looking east through the removed roof, showingitems that had been stored in the smokehouse

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After its restoration, the smokehouse was used as a static exhibitdemonstrating meat curing. It contained a smoke pit, curing meats, andbarrels of brine. The curing props were removed in the early 1980s.This provided unobstructed views of the interior walls, allowing foranalysis and documentation of the brickwork.

Description of the StructureThe smokehouse is a 12-foot 3-inch square brick structure with 8-feet high by 16-inch thick walls.

It has a pyramidal wooden roof that rises 8 feet above the eaves and a door centered on its west elevation.The remaining three elevations have three small vent holes equally spaced along the upper portions of the

walls. The construction of the building consists of two independent masonry walls, with Flemish bondcoursing on the exterior and 1:3 bond coursing on the interior. The walls were never anchored together,and the cavity between them was filled with excess mortar and rubble. The modern brick floor isapproximately one foot higher than the original sandy loam and oyster shell floor.

Flemish bond coursing 1:3 bond coursing

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Condition of the Architectural FeaturesIt appears that the brick and mortar units in the Benjamin Powell smokehouse began deteriorating

shortly after construction. The major mode of decay is disintegration into a powder. Brick is composedprimarily of grains of quartz (SiO2 ) or cristobalite (SiO2 ) in a potasium-aluminum-silicate glassy matrix.The exact composition varies depending upon the nature of the clay used to make the brick, as well as thefiring conditions. It deteriorates mainly through disruption of the matrix by mechanical stresses arisingeither from freeze/thaw cycles of water in the pores or from the crystallization pressures of soluble salts(Livingston, 1983). In the case of the smokehouse, the investigations determined that the primary cause ofthe deterioration was subflorescence, the crystallization of soluble salts in the brick walls. The brick unitswere also weakened by the removal of the cement stucco that had been applied to the exterior walls.

Aside from the damage caused by many years of brick deterioration, bulges formed on the exteriorwalls, especially along the upper portion of the south wall and at the southeast corner. The bulges were dueprimarily to the fact that the two walls were not anchored together and to internal pressures which causedthe outer wythe to pull away from the inner wythe of brick. The bulges on the south wall were obvioussigns of the smokehouse’s structural instability.

Another indication of instability was the cracks that formed on the interior walls disrupting structuralcontinuity and providing easy pathways for moisture to enter the building. In the center of each of the threecomplete walls, a large crack extended vertically upward from the bottom. The cracks were located in thecenter of each wall on the inside of the building. The crack on the north wall also emerged on the exterior.It is not known what caused these cracks, but the pattern is typical of uneven settlement of the foundations.Prior to the treatment, cracks were filled with a “soft” mortar to reduce moisture penetration and stabilizethe walls.

Close-up of a crack monitor

The assessment of the condition of the smokehouse was aided by the presence of the contemporarydairy. While the dairy has displayed few major signs of aging, the smokehouse has displayed manyobvious signs.

Interior east wall centercrack with crack monitorin 1987 (right) and withrepointing (far right).

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In 1979, the entire building was repointed with a Type N mortar, consisting of 50% lime and 50%cement, mixed with sand and water. Since 1980, the conservation program for the smokehouse consistedof the replacement of deteriorated brick and mortar when necessary using a “softer” mortar that had a high

lime and low cement content. The rate of deterioration was quantified at the loss of one centimeter oforiginal fabric every four years. In the summer of 2000, Colonial Williamsburg Foundation masonsstopped using cement in the mortar mix altogether. The replacement brick was fitted and tooled to match

the surrounding brick. Overall, the smokehouse has required some new brickwork and repointing nearlyevery two years. Foundation architectural conservators regularly monitored the smokehouse, watching forany sign of structural failure.

The switch to “softer” mortar necessitatedmore frequent repointings by the ColonialWilliamsburg Foundation masons.

New brickworkover the door

Repointed uppernorth wall

A ruler shows the amount of brick loss around theplug on the exterior north wall in 1987.

A brick core samplewas taken from theexterior north wallin 1983.

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The deterioration is most prevalant in the upper courses of the walls, starting approximately three to fourfeet from the ground up to the top of each wall. The upper courses, particularly at the corners, haverequired multiple repointing campaigns. Even the modern brick added during the 1950s restoration exhibitssigns of extreme deterioration, and as much as two to three inches of loss is visible on individual bricksthroughtout the interior and exterior of the smokehouse.

A minor cause of the brick deterioration, especially on the exterior east wall, is the local finchpopulation. The finches use the smokehouse as a source of salt and sediment that aid their digestion,taking away bits of the building in the process. Attempts to mitigate the bird problem such as rubbersnakes, plastic owls and alternate food sources have proven unsuccessful.

Deterioration at the southeast cornerof the south wall

Deterioration at the southeast corner of theeast wall. Note the bulge in the wall.

Close-up of the deterioration on the upper portionof the east wall

Excessive deterioration on the east wallcaused by erosion and birds

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InvestigationA comprehensive brick testing program was conducted on four Historic Area buildings, including

the Benjamin Powell smokehouse, from 1981-83. Research associated with the testing program included:1) environmental monitoring, such as ambient relative humidity, ambient air temperature, wall surfacetemperature and moisture content; 2) analysis of the brick and mortar; 3) investigation into brick deteriorationmechanisms and deterioration rates; and 4) research into eighteenth-century brickmaking in Williamsburg.Basically, the study provided the framework to understand the deterioration mechanisms of the smokehouse.The study showed that the powdering and spalling of the masonry units was the result of the crystallizationof soluble salts within the pores of the building materials.

In order to identify the destructive salt and its distribution within the smokehouse walls, non-destructive neutron gamma-ray spectroscopy examinations were conducted in 1982, marking the first timethis highly experimental instrument was used on a historic building. The measurement campaign (and asecond one undertaken in 1987) were made with equipment and personnel loaned by NASA’s GoddardSpace Flight Center in Beltsville, Maryland. The first campaign was intended to test the feasibility ofapplying the neutron probe for the assessment of the building’s condition. A set of twelve points in a three-foot-by-four-foot grid was measured on the north wall. The first measurement was made with the neutronsource on the outside of the building and the detector inside. Then the positions were switched andmeasurements repeated over the grid. The results were encouraging. They offered quantitative analysis of

the amounts of chlorine, hydrogen, and a number of other major elements in the brick and mortar. Also,voids were detected inside the wall when certain points showed transmission readings twice as high as theneighboring points (Livingston, 1991).

Gamma ray detector on the exteriornorth wall with the neutron source onthe interior wall (above), and associatedelectronics (right).

Gamma ray detector on the interiornorth wall with the neutron source onthe exterior wall.

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The first campaign’s data was supported by x-ray fluorescence and x-ray diffraction of samplesdone in 1983 at the University of Maryland (Livingston, 1984). The purpose was to apply x-ray fluorescencetechniques to study the chlorine distribution in deteriorated bricks from the smokehouse. Four samples of

brick were analyzed: two sound ones fromdifferent locations, one from brick showingmoderate deterioration, and one from badlydeteriorated brick. A relationship between thechlorine content of the brick and its conditionseemed apparent after two x-ray runs wereconducted. The best brick had a very lowchloride content (0.27%), while the completely exfoliating brick had a highchloride content (4.5%)(Livingston, 1983). Based on the x-ray fluorescenceand x-ray diffraction analysis, the salt present in the smokehouse walls wasfound to be sodium chloride. While groundwater would normally containother salts, such as potassium chloride or magnesium chloride, those werenot present in the wall samples, so it was concluded salt did not come fromrising groundwater (Livingston, 1984). Instead, the tests supported the theory

that the salt came from a manmade source such as the curing of meat or material deposited in the wallcavities during construction.

A second more extensive neutron probe campaign was carried out in 1987, using a more compactelectronics system. A total of forty-five points were measured on the north wall in a rectangular grid onone-foot centers. This provided a sufficient amount of data to allow the application of geostatisticaltechniques, and thus permitted the development of maps of elements within the wall, including salts

(chlorine) and water (hydrogen). Since the greatest salt concentration occurredabove the tide mark (highest point that ground water reaches in the wall), weagain ruled out the possibility of rising groundwater (Livingston, 1991). Wealso ruled out brine from the meat curing process as the primary source sincethe greatest concentration occurrred in the center of the wall on either side ofthe cavity. This information was supported by visual examination using aflexible fibre-optic boroscope with a mounted camera. The resulting imagesconfirmed the concentration of salt on the brick surfaces around the cavities.

Smaller, more sophisticatedequipment was used during thesecond campaign.

Intern Wayne Kille taking thebrick core samples.

Bryan Blundell, president ofDell Corporation, and TomTaylor using the boroscope.

Still and video equipment (above)captured images of the salt around thebrick cavities (left).

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An investigation to evaluate the physical nature of the interior wythes of masonry within thesmokehouse walls was conducted in June, 1988, by Atkinson-Noland and Associates, Inc., of Boulder,Colorado. The investigation used two methods of nondestructive wave transmission techniques: an ultrasonicpulse and a mechanical pulse, differentiated by the amplitude and frequency of the input signal. The

ultrasonic pulse measured an electro-acoustically generated pulse of low amplitude and a frequency ofapproximately 54 kHz. The ultrasonic method was abandoned because the 16-inch wall thickness, lowmaterial density, and possible hidden voids in the masonry proved impenetrable for the low-amplitude

pulse. The mechanical pulse utilized a simple mechanical blow with a medium-hardness hammer head,generating amplitude dependent on the force of the hammer blow and a frequency from 5-10 kHz. Whilethe mechanical pulse tests were successfully run on all grid points of both the north and south walls,confirming the presence of voids inside the walls, the exact size and location of the voids could not bedetermined (Kingsley, 1988).

Structural engineer Greg Kingsley checking forultrasonic pulse readings (above). Acousticalmachinery (left) was used to obtain readings from thetransmitter and receiver attached to the exterior northwall (right).

Greg using a mechanical pulse hammer on thenorth wall (far left) with the receiver attachedon the interior (left). Graphs were printed onsite (above).

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Since the filling of voids with an injectable mortar for the movement of salt through the brickswould be part of a salt extraction process, in October 2000 infrared thermography was used to locateinternal voids and to help guide the development of grout injection specifications. Two days prior to thetesting, an electric space heater was installed in the smokehouse, and the vents blocked to contain the heat.Infrared imaging was conducted by Mike Schuller, president of Atkinson-Noland & Associates, Inc., withan FLIR Prism DS portable camera using a Platinum Silicide infared CCD array to detect emitted radiationin the infrared portion of the electromagnetic spectrum. Withan active temperature drive working through the smokehousewall, temperature differences were used to locate internalvoids which act to interrupt heat transfer through the wall.The thermography results suggested that voids appeared tobe more prevalent towards the upper half of the walls,particularly on the south and east. Also noted were largecool areas at the southeast, northeast, and southwest cornersapproximately two to three feet below the roof line. Theregions were significantly cooler than the surroundingmasonry, indicating some sort of separation of the cornermasonry from the main wall mass.

To calibrate and supplement the thermal imaging, afiber-optic borescope was used for direct visual observationof the wall interior at some locations. The borescope wandwas inserted into voids in mortar joints or into 3/8-inchdiameter holes drilled into mortar joints. The borescopecorroborated the infrared images. Interior collar jointsvaried in width from 1/2 inch to 3/4 inch, and someseperation between the wythes was evident. The collar joints higher up the walls were generally open,with some debris and mortar blockage, particularly at the bed joints. Debris was more prevalent towardsthe base of the walls where debris had fallen within the joint. Occasional large, brick-sized voids wereobserved behind repair areas where it appeared that damaged brick had been removed, but clipped brickheaders had been installed in only the exterior wythe. Severely deteriorated and separated areas at the wall

corners were identified as requiring shoring duringthe injection process (Schuller, 2001).

Southwest elevation infrared image. The dark upperportions of the walls represent cool zones due to thepresence of internal cavaties that interrupt heattransfer through the wall. The orange lower portionsrepresent solid areas where more heat is transmittingthrough the walls. The yellow around the top of thewalls represents heat escaping between the wood plateand the brick walls. The southeast corner is obstructedby a large bush in this view.

Mike Schuller taking infrared images.

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Conservation ObjectiveThe investigations indicated that the structural instability was due to the fact that the two wythes in

the upper portions of the walls were not anchored together, and that the brick deterioration was mainly dueto subflorescence. The objective of the following treatment was to stabilize the structure by filling theinternal voids and bonding the inner and outer wythes together, and to extract as much salt as possible toreduce the rate of deterioration from subflorescence.

Treatment MethodologyA traditional method was considered for stabilizing the masonry walls. Injection grouting was

recommended to fill the voids and bind the masonry units together. The grout would also create a solidmass capable of transferring salts deeply embedded within the walls. The type of grout and the method ofinjection were not decided until shortly before the conservation treatment began.

Since subflorescence was the principle mechanism of deterioration, traditional methods ofdesalinization were tested. As early as 1982, Colonial Williamsburg Foundation conservators undertookexperiments using different types of clay poultices, including Fuller’s earth, Diatomaceous earth, Bentonite,Attapulgite, and Sepiolite. One-inch thick clay poultices were applied to the interior surfaces in 18-inchsquare test panels. Although clay poultices absorbed salts from the wall, it was not possible to entirelyremove the clay without damaging the already fragile brick surfaces. To mitigate this problem, Japanesepaper was used as a buffer between the brick and the clay. As long as the paper was saturated it clung to thewall. However, as soon as the paper began to dry, it fell taking the poultice with it, so a cleaner, moredurable material was sought. The best results were obtained with strips of paper pulp obtained from thepaper making operation at the Book Bindery, one of the interpretive programs at Colonial Williamsburg.The paper pulp was almost as absorbent as the clay, it remained on the wall after drying, and the stripspeeled away from the surfaces without abrading the bricks (Taylor, 2002).

In the spring of 2000, a treatment proposal for the smokehouse was developed based oninvestigations, research, and professional consultations (Hannah, 2000). The initial plan was to distributethe proposal to prospective contractors and obtain cost estimates in the fall of 2000. Funds would beallocated in 2001 for the project that would begin in May or June. The engineering firm, Atkinson-Noland& Associates, Inc., which had assisted in the investigations since the early 1980s, indicated that it wantedto do the job. However, the firm already had commitments for other projects during the summer of 2001,so it was decided to accelerate the treatment and undertake the work during the winter of 2000 due in partto the availability of the engineer and in part to the increasing instability of the walls.

With the switch from summer to winter atmospheric conditions, instead of poulticing the exteriorwalls, the process was turned inside out. It was decided to poultice the interior surfaces of the buildinginstead. Using heaters, dehumidifiers and fans, conditions inside the smokehouse could be stabilized withhigher temperature and lower relative humidity levels than in the enclosure. This difference in ambienttemperature and relative humidity would help draw the water, which would be continuously sprayed onthe exterior walls, through the bricks and carry the salts into the poultice on the interior walls. Ample waterflow through the walls was expected to draw the salts in the walls into the poultice.

Poulticing the interior had three benefits: 1) a smaller surface area to poultice; 2) less risk of waterfreezing in the poultice; and 3) easier to maintain a 30% differential in the relative humidity levels betweenthe interior and the exterior. Around the exterior of the building an enclosure, less substantial than originallyplanned, was constructed to keep ice and snow off the exterior walls. This decrease in size was a benefit

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since the Benjamin Powell complex was to remain open for interpretation during the treatment process.A sufficient quantity of paper pulp could not be located in time for the project. At the suggestion

of the project engineer, an alternate material for the poultice was sought, consisting of a cellulose fibrematerial. The substitue of choice was non-chlorine toilet paper. Although there wasn’t time to conduct on-site tests on the toilet paper poultice prior to treatment, it was successfully tested in the engineer’s lab anddeemed appropriate for the project (Schuller, 2001).

Treatment ProceduresThe treatment began on November 13, 2000 with the arrival of Wayne Ruth, president of Masonry

Solutions, Inc., and his crew. Over the next four days, the exterior of the building was reinforced withwood (4 x 4) bracing, 954 injection ports were drilled in the interior andexterior walls, 181core samples were collected, a temporary aluminum-faced insulation board ceiling was installed in the building, and anenclosure made of wood slats with horizontal support ribs covered withplastic sheeting was constructed. Garden hoses (which had holes pokedin them) were positioned along the tops of the ribs, providing a continuouslight spray of water on the tops of the exterior walls.

The next five days consisted of the grout injection and firstpoulticing cycle. The interior and exterior walls were wetted to aid inboth the grouting and poulticing procedures. The lime-based grout (havingthe composition of a 1:2:10 mortar mix, with some modifiers, but nopolymer bonding agents that would reduce the vapor permeability of themix) came pre-mixed in bags prepared by the contractor and was mixedwith a pre-determined

amount of water in a 30-gallon Nalgene container. Justenough grout was prepared that could be injected within anhour of mixing, and what was not used was discarded. Thegrout was injected row by row from the bottom up at aninjection pressure of 8 to 12 psi, the holes were plugged withwooden dowels as the grout spread through the walls, andthe number of batches and their injection locations were

recorded.The poultice mixing

procedure consisted of: 1) cutting aroll of 2-ply toilet paper with a hacksaw; 2) removing the cardboardinner roll; 3) cutting and flattening the toilet paper; and 4) mixing toilet paper and

water in a 30-gallon plastic drum with a drill and metal stirrer. Just enough water was added to the toiletpaper to make the final consistency similar to papier-mache. Nearly 650 rolls of toilet paper were used forthe first application, and the contractor’s crew applied the poultice by hand to the interior walls from 1/2”to 1” thick depending on the wall contours.

The wall core samples and two Ziploc bags with control samples of the poultice were mailed toAtkinson-Noland & Associates, Boulder, Colorado, for testing. One temperature/relative humidity gauge

Romeo Thomas (left) injecting grout while WayneRuth uses stethescope to track its progressionthrough the wall.

Exterior bracing constructed tosupport the walls during thegrouting process.

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was placed inside the smokehouse and a second gauge was placed insidethe plastic enclosure to ensure that relative humidity levels inside thesmokehouse were kept nearly 30% lower than those in the enclosure.

On the last day of the first cycle four poultice samples werecollected by hand from each of the interior walls. The contractor’s crewthen removed the rest of the first poultice, discarded the material in plasticbags, and mixed (using nearly 630 rolls of toilet paper) and applied thesecond poultice the same way as the first poultice. The wood bracing wasremoved, and more grout was mixed and injected into the holes that wereblocked by the braces. The propane heater that had been hooked up in thesmokehouse to aid in the grout curing process was removed, and twoelectric heaters and a dehumidifier were placed inside to keep thetemperature and relative humidity in the smokehouse at levels conducive to pulling water through thebrick walls, collecting the salt embedded in the brick, and depositing it in the poultice.

During the seven day second cycle, a three-gallon compressed air sprayer was used to wet thedrying poultice on the north and east walls (which had become stiff and detached from the masonry inplaces) helping it remain absorbant and attached to the walls. The water pressure was adjusted to increasethe amount of water coming out of the hose that was spraying water onto the exterior wall surfaces. At theend of the cycle, poultice samples were again taken by hand from the same points on each wall, and thepoultice was removed in the same way as the first application.

The third application was mixed and applied just as the previoustwo were, except nearly 700 rolls of toilet paper were used so that athicker poultice layer could be applied to the contours of the bricksurfaces. A five-gallon bucket with extra poultice was left in thesmokehouse to fill any cracks that might appear. During the sixteenday third cycle the poultice developed yellow and browndiscolorations. There was no clear pattern or concentration ofdiscoloration, but there were varying shades of yellows and browns.The discoloration was fungal

growth associated with the extended time that the poultice remained onthe walls (Charola, 2001). The poultice on the lower portions of thesouth and west walls remained very wet to the touch, while the poulticeon the north and east walls was noticeably drier, especially along theupper portions. The hoses kept slipping down the enclosure, supplyingonly the lower halves of the walls with water, so they were adjusted tospray higher. Additional holes were punched in the hose spraying on thenorth and east walls since the poultice was drying out too quickly on theinterior walls. On the other hand, some holes had to be sealed in thehose spraying on the south and southwest walls where the poultice hadbecome too saturated. Periodically, ice had to be removed from theenclosure and plastic had to be reattached to the ribs of the enclosure.Twelve days into the third poultice cycle, samples were taken from theinterior walls in the same manner as the previous two.

Tom Taylor fixing the enclosure

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The third poultice was removed and the fourth applied like the previous applications. However,less toilet paper was used (only about 600 rolls), and it was onlyapplied approximately 3/4” thick over most of the walls. Crackssoon appeared in the poultice and were repaired using extrapoultice material. The enclosure again had to have ice brushedoff it and loose plastic sheets re-stapled due to inclement weatherduring the fourth cycle. Inside the smokehouse, Clean Sorb, agranulated absorbent material, was spread on the floor to soakup excess water. Samples were collected for testing to see ifsalt was being flushed down onto the floor. A 16-inch 3-speedoscillating fan was installed in the smokehouse to assist inmaintaining the 30% differential between the interior and exterior conditions. Discoloration from fungalgrowth appeared on the poultice during the 35 day cycle.

As with the previous applications, samples were taken, the fourth poultice was removed and thefifth was applied. More toilet paper was used (about 700 rolls) thanduring the previous application, allowing the poultice to be applied atleast 1” thick. During the 49 day cycle, discoloration again appeared onthe poultice. Saturated poultice started to pull away from the walls inplaces due to excess water, and a section of poultice fell off the bottomcenter portion of the south wall. Several sections of poultice fell off thesouth wall before the fifth poultice was removed. The poultice on thesouth wall was routinely patted down to force out some of the excesswater and air between the poultice and the wall. Water continued to poolon the smokehouse floor, and absorbent material was regularlyreplenished after samples were collected for testing. In addition, limebloom was discovered on the exterior north and northwest walls.

When the fifth poultice was removed , a considerable amount ofblack fungal growth was found on the brick and mortar, especially on the

north wall (far more than we saw growing on the surface of the poultice). The fungus was not removedprior to the application of the sixth poultice that same day. Nearly 700 rolls of toilet paper were again usedto provide a poultice layer 1” to 1 1/2” thick.

As with the other applications, cracks began to appear in the sixth poultice the day after it wasapplied. The cracks developed as the poultice shifted on the wall, andadditional poultice was applied to fill the cracks. Poultice on the upperportions of the east and north walls was again drier than the material onthe other walls, so a sprayer was used to prevent the poultice from dryingout before it had a chance to absorb the salt. Discoloration re-occurred,and a couple of weeks into the poultice cycle fruiting bodies appeared onthe southwest wall and an unpleasant odor pervaded the inside of thebuilding. Both heaters were turned off to lower the temperature in thesmokehouse below 80 degrees Farenheit, and to decrease the conditionspromoting excessive fungal growth. Near the end of the sixth cycle,poultice samples were again taken for testing.

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After 47 days, the sixth poultice was removed and the bare interior walls were sprayed with waterto remove some of the fungal growth from the bricks. A fungicide, BORA-CARE, was lightly sprayed on

the affected areas of the walls before the seventh (and final)poultice was applied. The fan and dehumidifier wereremoved from the building and the enclosure was adjustedon the west side around the door to allow it to stay open tothe outside. The hoses around the smokehouse wereremoved, and two soaker rings were positioned at thenorthwest and southwest corners inside the enclosure tomaintain the humidity differential without spraying waterdirectly on the exterior walls. Inside, the poultice, whichhad been applied about 1 1/2” thick, dried evenly on allfour walls, and the fungicide appeared to be working sincethere was very little fungal growth.

The soaker rings were turned off shortly beforethe contractor’s crew returned after 18 days to remove the final poultice. The fan was removed, poulticesamples were taken, the remainder was removed from the walls, and the floor was cleared of poulticeremnants. The enclosure and hoses were disassembled. A soft brush and small broom were used toremove poultice remnants from the the interior walls.

The Colonial Williamsburg Foundation’s Office of Architectural Collections Management staffassisted the contractor’s crew and documented the November 13, 2000 to May 11,2001 treatment process. They collected and mailed samples for testing; maintainedthe heaters, fan, dehumidifier, poultice and enclosure; and inspected the smokehousetwice a day during the poulticing. For twelve months following the final poulticeremoval, they recorded the daily ambient temperature and relative humidity readingsinside and outside the smokehouse. The project documentation is compiled in

five notebooks containing: 1) the initial treatment proposal; 2) plans and specifications; 3) the project dailylog; 4) test results; and 5) photographs. The notebooks are on file in the Office of Architectural CollectionsManagement.

Connie Torrain removing fungal growth from theinterior walls before applying fungicide

Dani Jaworski recording fungalgrowth on the third poultice

Contractor’s foreman drilling coreswhile Architectural Collections staffrecords the holes and collects samples

(l to r) Tom Taylor, Wayne Ruth andMike Schuller study the exterior northwall after the treatment

17


ResultsThe conservation objectives were met during the treatment process. Before the grouting, the

concentration of salts around the voids in the center of the walls prevented the walls from drying out. Thegrout injection succeeded in stabilizing the walls by filling the internal voids and bonding the interior andexterior wythes together, thus facilitating the desalinization treatment.

The cellulose fibre poultice succeeded in removing a larger than expected amount of salt, over15% by weight of the dried poultice. It is estimated that at least 38 pounds of salt were removed in theseven poultice applications. Although this does not account for all of the salt calculated from the pre-treatment samples, salt was also found in the absorbent material samples taken from the smokehouse floor.This suggests that some of the salt was flushed out of the walls into a nearby surface drain, lowering the saltcontent readings in the poultice samples.

Based on our year-long post-treatment monitoring, the environment inside the smokehouse hasgreatly improved. There is significantly less salt in the walls, less moisture in the masonry, and the ambienthumidity inside the smokehouse is now comparable to the outside. One of the unexpected results of thesalt extraction was the establishment of a environment more favorable to fungal growth

This treatment was experimental, because Colonial Williamsburg has never poulticed an entirebuilding before. With very little literature available about poulticing whole buildings, we did not knowhow long the poultice should remain on the walls or how much water should be applied to aid the extractionprocess. As a result of the accelerated schedule there was no time to establish the most effective applicationcycles or the amount of water needed. During the treatment, we experimented with short intervals andlong intervals. We recommend a 5 or 7 day cycle with the water turned off during the last two daysallowing the walls to dry out pulling more salts into the poultice. We learned that conducting treatments ofthis type in this region are more effective in the winter because it is easier to maintain the RH differential.

The test results (at left) confirm ourbelief that the salts were flushed out ofthe walls, floor and nearby soil duringthe treatment. The measurements showthe percent of sodium chloride byweight.

18


Project Statistics♦ The treatment began on November 13, 2000 and concluded on May 11, 2001.

♦ Thirteen people worked on the six-month project.

♦ A total of 118 interior and 63 exterior brick core samples were taken.

♦ Approximately 210 gallons of lime-based grout were used

♦ Nearly 5,000 rolls of 2-ply toilet paper were used.

♦ There were seven poultice applications.

♦ 141 poultice samples were tested for salt content.

♦ The Architectural Collections staff checked the heaters, dehumidifier, fan, temperature/relativehumidity sensors, and poultice inside the smokehouse, and also checked the sensor, hoses andplastic sheeting in the enclosure twice a day during the project.

♦ Temperature and relative humidity readings inside and outside the smokehouse were recordedeach day for a year after the removal of the seventh poultice application.

In the end, this treatment process has proven that poulticing using cellulosic material can be extremelysuccessful, and that it has application to other conservation issues dealing with weakened masonry units.

AssessmentWhile this treatment method was successfully performed on the Benjamin Powell smokehouse,

there are a number of things that we would do differently when using this treatment on another wholebuilding:

1) Test more pre-treatment core samples from different locations in the walls. This would providefor more points of comparison between the before and after treatment results.

2) Regularize the poultice removal process with 7-10 days duration for each application. Thiswould alleviate the fungal problem.

3) Regulate water for more uniform application, reducing the amount of water toward the end ofthe poultice cycle. This would help provide optimal poultice conditions to extract as much saltas possible and to permit the walls to dry out.

4) Test floor and soil samples before and after the treatment, to see how much salt might have beenflushed out of the walls into the floor and ground.

5) Use perforated hoses, anchored by clamps to the enclosure frame, to provide a more constantspray on the exterior walls. This would enable more consistent flushing action through thewalls.

19


Amoroso, G. G. and V. Fassina. Stone Decay and Conservation. New York: Elsevier Science PublishingCompany, Inc., 1983.

Ashurst, John and N. Ashurst. Practical Building Conservation: Bricks, Terracotta, & Earth. Hants,UK: Gower Technical Press, Ltd., 1988.

Baer, Norbert S., et al., eds. Conservation of Historic Brick Structures. Dorset, UK: Donhead Publishing,Ltd., 1998.

Charola, A. Elena. “Analysis of Poultices for Desalination: Benjamin Powell Smokehouse in ColonialWilliamsburg”. Unpublished report on file, Office of Architectural Collections Management,Colonial Williamsburg Foundation, Williamsburg, 2001.

Evans, Larry, R. Livingston, T. Taylor, and J. Trombka. “Diagnosis of Building Condition by the Neutron/Gamma Technique”, Building Performance: Function, Preservation and Rehabilitation, STP901, G. Davis, ed. American Society for Testing of Materials, Philadelphia, (1986): 165-180.

Evans, L., R. Livingston, T. Taylor, and J. Trombka. “Neutron/Gamma-ray Techniques for Investigatingthe Deterioration of Historic Buildings”, Nuclear Instruments and Methods in Physics Research,A242 (1986): 346-351.

Evans, L., R. Livingston, T. Taylor, and J. Trombka. “Neutron/Gamma Ray Techniques for Mapping theDistribution of Contaminants in Walls”, Transactions of the American Nuclear Society, vol. 45(1984): p.255.

Kingsley, Greg R. and J. L. Noland. “Nondestructive Evaluation of the Benjamin Powell Smokehouse,Colonial Williamsburg Virginia, Using Stress Wave Transmission Methods”. Unpublished reportprepared by Atkinson-Noland and Associates on file, Office of Architectural CollectionsManagement, Colonial Williamsburg Foundation, Williamsnurg, 1988.

Kingsley, G., R. Livingston, J. Noland, and T. Taylor. “Nondestructive Evaluation of a 19th-CenturySmokehouse in Colonial Williamsburg”. Proceedings, International Conference on StructuralStudies, Repairs and Maintenance of Historic Buildings, Institute of Computational Mechanics,Southampton, UK, 1995.

Livingston, Richard A. and T. Taylor. “Diagnosis of Salt Damage to a Smokehouse in ColonialWilliamsburg”, Bulletin of the Association for the Preservation Technology International, vol.XXIII, no. 3 (1991): 3-12.

Selected References

20


Livingston, R. A. “Examination by X-Ray Fluorescence of Deteriorated Brick From ColonialWilliamsburg”. Unpublished report on file, Office of Architectural Collections Management,Colonial Williamsburg Foundation, Williamsburg, 1983.

Livingston, R. A. “X-Ray Analysis of Brick Cores From the Powell-Waller Smokehouse, ColonialWilliamsburg”. Unpublished report on file, Office of Architectural Collections Management,Colonial Williamsburg Foundation, Williamsburg, Virginia, 1984.

London, Mark. Masonry. Washington, DC: The Preservation Press, 1988.

Manzouri, T., P. B. Shing , B. Amadei, M. Schuller, and R. Atkinson. Repair and Retrofit of UnreinforcedMasonry Walls: Experimental Evaluation and Finite Element Analysis, Report Number CU/SR-95/2. University of Colorado at Boulder, November 1995.

Massari, Giovanni and I. Massari. Damp Buildings, Old and New. Rome, Italy: ICCROM, 1993.

Ruth, Wayne T. and M. Schuller. “Grout Injection Specifications”. Unpublished report prepared by MasonrySolutions, Inc., and Atkinson-Noland & Associates, Inc., on file, Office of Architectural CollectionsManagement, Colonial Williamsburg Foundation, Williamsburg, Virginia, 1999.

Samford, Patricia. “Benjamin Powell Smokehouse, Block 7”. Unpublished report on file, Department ofArchaeological Research, Colonial Williamsburg Foundation, Williamsburg, VA, 1989.

Schuller, Michael P. “Infrared Thermography Testing”. Unpublished report prepared by Atkinson-Nolandand Associates on file, Office of Architectural Collections Management, Colonial WilliamsburgFoundation. Williamsburg, 2001.

Schuller, M., W. Ruth, and S. Albert. “Repairing Common Masonry Problems by Grout Injection”.Proceedings of the Seventh International Conference on Structural Faults and Repair,Edinburgh, Scotland, July 1997.

Stockton, Robert P. The Great Shock. Easley, South Carolina: Southern Historical Press, Inc., 1986.

Taylor, Thomas H. et al. “Compilation of Brick Studies and Reports”. Unpublished reports on file, Officeof Architectural Collections Management, Colonial Williamsburg Foundation, Williamsburg,Virginia, 1981-86.

Warren, John. Conservation of Brick. Oxford, UK: Butterworth Heinemann, 1999.

Winkler, Erhart M. Stone: Properties, Durability in Man’s Environment. New York: Springer-Verlag,1975.

21


Appendix A

0

2

4

6

8

10

12

14

16

NW N E S SW

Percent sodium chloride content by dry weight of poultice

Sampling Location

% in 1st poultice

(11/19/00 to 11/22/00)

% in 2nd

poultice (11/22/00 to

11/29/00)

% in 3rd


12/15/00)

% in 4th

poultice (12/15/00 to1/19/01)

% in 5th


3/07/01)

% in 6th


4/23/01)

% in 7th


5/11/01)NA9 0.00 0.29 13.78 0.43 0.23 0.14 0.76ND7 0.20 0.69 13.19 0.47 0.21 0.22 0.16NF7 0.37 2.28 >14.11 1.08 3.86 0.22 0.05NI7 0.40 2.02 6.06 5.74 10.55 0.47 0.13EA7 0.07 0.06 8.18 1.66 0.07 0.38 0.22ED7 0.07 0.13 12.15 2.38 1.38 0.21 0.13EF7 0.51 0.90 10.11 2.19 0.77 0.08 0.09EI7 0.15 0.83 4.47 10.40 7.01 4.37 0.18SA8 (N/A) >13.54 0.22 0.10 0.23 0.13 0.11SD7 13.51 4.54 0.21 0.86 0.11 (N/A) 0.07SF7 8.20 >13.52 0.17 0.10 0.24 0.07 0.07SI8 1.34 >12.31 1.22 0.05 0.22 0.08 0.05

SWA3 14.88 10.26 2.64 0.31 (N/A) 0.12 0.06SWD3 6.82 6.85 5.36 0.64 (N/A) 0.07 0.07SWF2 9.57 >13.95 2.31 0.19 (N/A) 0.13 0.08SWI2 4.49 15.60 >15.57 1.03 (N/A) 0.22 0.06

NWA6 0.00 0.05 2.34 0.36 1.19 0.23 0.06NWD6 0.05 0.18 12.27 0.79 0.58 1.01 0.14NWF5 0.73 1.16 >14.33 1.09 0.48 0.09 0.14NWI5 0.07 0.95 8.04 1.41 1.14 0.15 0.35

Poultice Control 0.06 0.08 0.08 0.07 0.11 (N/A) (N/A)

3rd over Linte l

11.27

3rd ove r-lapping 5.31

Floor Absorbent

Control0.18

Used Floor Absorbent

3.88 (1/05/01)

6.76 (1/08/01)

0.61 (1/29/01)

Use d Absorbent from base

of walls

0.23 (N) 0.18 (S) 0.37 (E) 0.40 (W)

(2/27/01)

22


** Represents at least a 4.5% increase

** Samples taken due to excessive discoloration

** N/A = No sample available

** Represents at least a 4.5% decrease

** Different tests methods were used depending upon the amount of salt present in each sample. The margin of error for the smaller amounts is +/- .02%, while the margin of error for the larger amounts is +/- .20%.** We feel sampling reveals more of the salt extracted during the 3rd poultice, because water had been standing since the middle of that cycle.

ecitluoPfothgieWyrDybtnetnoCedirolhCmuidoStnecreP

gnilpmaSnoitacoL

ts1ni%ecitluop

dn2ni%ecitluop

dr3ni%ecitluop

ht4ni%ecitluop

ht5ni%ecitluop

ht6ni%ecitluop

ht7ni%ecitluop

9AN 00.0 92.0 87.31 34.0 32.0 41.0 67.0

7DN 02.0 96.0 91.31 74.0 12.0 22.0 61.0

7FN 73.0 82.2 11.41 80.1 68.3 22.0 50.0

7IN 04.0 20.2 60.6 47.5 55.01 74.0 31.0

7AE 70.0 60.0 81.8 66.1 70.0 83.0 22.0

7DE 70.0 31.0 51.21 83.2 83.1 12.0 31.0

7FE 15.0 09.0 11.01 91.2 77.0 80.0 90.0

7IE 51.0 38.0 74.4 04.01 10.7 73.4 81.0

8AS A/N 45.31 22.0 01.0 32.0 31.0 11.0

7DS 15.31 45.4 12.0 68.0 11.0 A/N 70.0

7FS 02.8 25.31 71.0 01.0 42.0 70.0 70.0

8IS 43.1 13.21 22.1 50.0 22.0 80.0 50.0

3AWS 88.41 62.01 46.2 13.0 A/N 21.0 60.0

3DWS 28.6 58.6 63.5 46.0 A/N 70.0 70.0

2FWS 75.9 59.31 13.2 91.0 A/N 31.0 80.0

2IWS 94.4 06.51 75.51 30.1 A/N 22.0 60.0

6AWN 00.0 50.0 43.2 63.0 91.1 32.0 60.0

6DWN 50.0 81.0 72.21 97.0 85.0 10.1 41.0

5FWN 37.0 61.1 33.41 90.1 84.0 90.0 41.0

5IWN 70.0 59.0 40.8 14.1 41.1 51.0 53.0

ecitluoPlortnoC 60.0 80.0 80.0 70.0 11.0 A/N A/N

letnilrevO 72.11

doowrevO 13.5

tnabrosbAlortnoc 81.0

desUtnabrosba

88.3)10/50/1(

67.6)10/80/1(

16.0)10/92/1(

23


The poultice samples were dried, weighed (circled, above right) and tested for chloride content.

tnetnoCtlaSdnanoitaruDecitluoP

noitaruD selpmaSnekaT

yrdyb%tlaSthgieW

thgieWtlaS)bl(

ecitluoPts1 syad3 syad3retfA 32.3 1.6

ecitluoPdn2 syad7 syad5retfA 10.5 5.9

ecitluoPdr3 syad61 syad21retfA 43.7 0.41

ecitluoPht4 syad53 syad33retfA 65.1 0.3

ecitluoPht5 syad74 syad74retfA 77.1 4.3

ecitluoPht6 syad74 syad44retfA 56. 2.1

ecitluoPht7 syad81 syad81retfA 54. 9.0

24


* Average moisture content of drill dust taken from 4” and 9” depths at each location

slairetaMfothgiewyrDybtnetnoCerutsioMdnaedirolhCmuidoStnecreP

tsuDllirDnoitacoLelpmaS

thgieWybedirolhCmuidoStnecreP *thgiewyb%,tnetnoCerutsioM

noitidnoClanigirO gnicitluoPretfA gnicitluoPretfA

6AWN 10.0 00.0 85.5

6DWN 00.0 00.0 05.0

5FWN 90.0 00.0 02.0

5IWN 69.2 00.0 02.0

9AN 20.0 00.0 2.32

7DN 61.0 00.0 00.0

7FN 07.1 00.0 02.0

7IN A/N 00.0 02.0

7AE 50.0 00.0 07.6

7DE 00.0 00.0 00.1

7FE 00.0 00.0 00.0

7IE 66.1 00.0 04.0

8AS 00.0 00.0 0.9

7DS 00.0 05.0 6.7

7FS 00.0 05.0 00.0

8IS 38.1 00.0 06.1

3AWS 00.0 00.0 07.7

3DWS 00.0 00.0 09.3

2FWS 00.0 00.0 02.0

2IWS 45.1 00.0 00.0

25


Appendix B

26


The bulges and excessive loss of brickand mortar on the smokehouse arevisible signs of deterioration that thecontemporary dairy (below right) hasnot developed.

27


Condensation developed on the interior corners before the treatment (above left).After the treatment the corners show no sign of condensation (above right)

Regular ambient temperature and relativehumidity readings were taken after the initialbrick testing program.

Moisture meters read the moisturelevels in the walls.

28


The enclosure erected around the smokehouse hadgarden hoses (with holes punched in them) attachedalong the tops of the wooden supports. The hosescontinuously sprayed water on the exterior wallsaiding in the desalinization process.

29


The exterior walls were injected first.The walls were wetted before andduring the injection process to helpclean out any debris on the surface ofthe brick or in the injection holes.

The grout was prepared inside theback of a storage truck because of theunpredictable winter weather.

30


The grout was injected row by row starting from the bottom up at an injection pressureof 8 to 12 psi. The holes were plugged with wooden dowels as the grout spread throughthe walls, and debris and excess mortar were washed off the walls.

31


A wooden stirrer was used to mix the test poultice (above left), but the consistency wastoo lumpy. An electric drill with a metal rod was used for the actual poultice applications(above right).

The electric drill and metal rod (left) createda more papier-mache consistency thatadhered better to the walls.

32


The poultice was applied by hand ½” to 1¾” thickdepending on the brick surface contours.

The poultice on the south wall becametoo saturated at times causing patchesof poultice to fall off (note remnants onthe floor). Extra poultice material wasused to fill the spaces.

33


A dehumidifier and heaters helpedmaintain an approximately 30%relative humidity differentialbetween interior and exteriorambient conditions.

Fans were used to even out thepoultice drying action on all fourwalls during the last three poulticecycles.

Absorbent material was spread on thefloor during the fourth and fifthpoultice cycles to collect excess waterthat was pooling in several places.

Temperature/Relativehumidity gauges monitoredthe ambient conditionsinside the smokehouse andthe enclosure.

34


At the completion of the treatment process, Mr. Benjamin Powell thanked Tom Taylor,Mike Schuller and W ayne Ruth (left to right) for their efforts in conserving thesmokehouse.

benjamin powell smokehouse - colonial williamsburg...benjamin powell smokehouse treatment report...

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