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Journal of Cultural Heritage 9 (2008) e69ee72

Original article

Conservationerestoration of cloisonne windows: A case study

Jordi Bonet

J.M. Bonet Vitralls S.L., Asturies 6, 08012 Barcelona, Spain

Received 30 March 2008; accepted 5 August 2008

Abstract

Restorationeconservation of cloisonne glass is a little known method which requires specific techniques, materials, and skills. The steps taken inthis method are very different from the common steps taken in stained glass conservation. In light of the fact that there are few objects manufacturedand preserved in this method, conservationerestoration interventions are scarce, four in total to the author’s knowledge, and as a result thebibliography is quite short as well. There is a great need to share methodologies and criteria about this method and to publish articles withdescriptions and the results of the procedures used by conservators. In this article the steps taken to conserve a cloisonne glass window areexplained. The restoration focused on minimal intervention, which, due to the technique and deterioration of the panel, was particularly chal-lenging. The window was recently brought to light thanks to an antique dealer who was able to identify the piece through careful investigation. Thewindow is assumed to be the work of Frederic Vidal Puig, the only known Catalan artisan who used this technique between 1899 and 1904.� 2008 Elsevier Masson SAS. All rights reserved.

Keywords: Cloisonne Glass Company; Frederic Vidal Puig; Glass beads; Pfister and Barthels; Stained glass

1. Historical background

Stained glass lights manufactured in Catalonia from the endof the 19th century until the beginning of the 20th centurycontributed to the great legacy and heritage of the stained glassindustry from this era. These contributions are a sign of thelong history of economic, social and cultural growth in Cat-alonia in a way that was very different from the rest of Spain.

At the same time there were many other stained glassstudios. All of these manufacturers were clearly led by theprinciples of technical improvement and artistic developmentin the stained glass industry.

As a result, techniques and procedures that were onceavant-garde [1] like tricomia, glass doubling, glass engravingand etching, gilded lead or lead cames encased in brass can beseen on some of the stained glass from this period.

Yet there is still one technique left to be mentioned, onewhich is probably the rarest due to the few objects manufac-tured by this way and to the originality of the process and

E-mail address: jordibonet@vitrallsbonet.com

1296-2074/$ - see front matter � 2008 Elsevier Masson SAS. All rights reserved.

doi:10.1016/j.culher.2008.09.001

materials chosen. Truth be told, it was forgotten long ago andthe recovery of the whole process was a brilliant researchproject done by Manuel Garcia Martın [2,3] and brought tointernational attention by Joan Vila Grau [4]. Before GarciaMartin’s publications this technique seemed condemned toa slow extinction and the windows built this way did not evenhave a name.

Cloisonne glass may be confused with the procedure knownas email cloisonne but it is quite different. In the latter, thinmetallic strips are separated by a glass powder with a lowmelting point. In the former, however, metal strips are appliedbut no enamel or firing is used.

The patent rights for the production of cloisonne windowswere granted to Pfister and Barthels in 1897. As businesspartners they ran a firm named The Cloisonne Glass Companywhich was located in the city of London at 40 Berners Street/Oxford Street. According to art historians there was alsoanother cloisonne producer who manufactured the pieces thatcan be found in Catalonia and who was a former apprentice inthat London firm.

This producer was the son of Frederic Vidal i Javelı,founder of the F.Vidal firm dedicated to interior decoration.

e70 J. Bonet / Journal of Cultural Heritage 9 (2008) e69ee72

In 1898, he sent his son, Frederic Vidal Puig (1882e1950), toLondon. By August 1899, after just 1 year, he seemed to havelearned enough to produce lights in the cloisonne technique inBarcelona. Shortly after coming back to Barcelona he startedteaching his father’s workers about the new procedure.However, after six months they refused to continue learningabout it, arguing that it was ‘‘too difficult’’.

In 1904 Vidal Puig went to South America where he spent13 years without partaking in any artistic activity. When hecame back to Barcelona he took over his father’s business buthe never manufactured cloisonne windows again. Therefore, itis assumed that any cloisonne glass preserved in Barcelonawas produced by the F.Vidal Firm between 1899 and 1904.

Strobl [5] was able to describe the construction method asfollows.

A full size cartoon is set under a glass sheet with the samemeasurement. The thickness of the panel can vary from 6 to9 mm. The metal strips are bent and placed over the drawn linesand glued with Arabic gum. When this structure is set and isstuck to the glass, partitions are filled with the required particles.The choice of materials used varies since there can be crushedglass filtered through sieves to the desired size or glass beads.

When the whole surface is covered, the glass powder andbeads are fixed with fish glue. Finally the glue is applied whenwarm and with a tiny portion of potassium dichromate.

In some cases as the glue dries the two layers are coveredwith a thin 3 mm glass. The sides of this sandwich can beclosed either with thin putty strips milled to the requiredthickness or sealed with copper foil. When putty is used theedge of the two pieces of glass is covered with adhesive paper.

In Barcelona the Bertran i Serra collection of cloisonneglass manufactured by Vidal Puig survived and was given tothe Town Hall. Surprisingly enough, it is not currently beingexhibited and there has been no news of the conservationconditions and the current state of the windows since the lasttime they were exhibited 20 years ago.

2. Conservationerestoration considerations

Despite the fact that the author of the patent states thecloisonne technique’s long-term performance and ease ofrepair [6], this claim is far from true.

The weak nature of the window is responsible for thedifficulty in preserving and conserving this type of stainedglass, but even transportation and storage becomes a difficulttask when beads, pieces of dried putty, and metal stripsbecome loose.

Organic adhesives such as Arabic gum and fish glue makethe conservation of the windows extremely dependent onenvironmental conditions, especially humidity fluctuation. Fishglue is hygroscopic [7] so a high level of humidity can reversethe initial adhesive strength of the glue. Moreover, suddenchanges in humidity or a lack of moisture in the air causes theglue to become very brittle and weak and it becomes both lessadhesive and cohesive [8]. Furthermore, the different expansioncoefficient of the materials employed is also responsible for theloss of adhesion between the glass particles.

In the conservationerestoration of cloisonne windows wemust take into account that these objects are not only works ofart but also perform a practical purpose serving as windows,tables, doors, lampshades, etc.

Conservationerestoration of cloisonne panels raises somedilemmas that must be addressed. Their weak nature makes ituncertain whether the use of minimal intervention andreversibility can truly provide a reliable long-term preserva-tion strategy as it is stated in the conservation guidelines [9].

When it comes to cloisonne windows minimal interventionon the original materials cannot ensure a long-term preserva-tion but nonetheless they must be respected [10]. It is essentialthat, when original materials are used on cloisonneconservationerestoration, the preservation of the objectundergoes careful preventive conservation in a controlledenvironment and that it be subject to regular inspection.

Other conservationerestoration methods of cloisonne[2,11] glass have separated the glass powder and beads,cleaned and sorted the colours, and then reconstruct the glassbead layer over a new float glass using silicon to seal the edge,instead of putty, and to glue the metal strips.

Such an intervening approach can reproduce the originalaspect of the object, and may offer stronger adhesion andlonger durability, but the originality and authenticity of thewindow is not preserved.

On the other hand the use of polymeric materials such asSilicone or Paraloid may solve adhesion problems but theyalso bring out some others like an uncertain reversibility or noreversibility at all, no adhesion to original materials, yellow-ing, etc.

Conservatorserestorers not only have the responsibility topreserve the physical structure of an object but also to preservethe choice of material made by the artist and artisans [10].

3. A case study

The window presented in this paper is a rare piece becauseit shows the outline of a human figure in cloisonne glass(Fig. 1). The window shows a figure which has been identifiedas Saint Anthony. It had suffered different levels of deterio-ration and damage, as well as cracks in the base and coverglass. However, all the metal strips were found in their originalpositions.

Prior to any conservationerestoration a detailed workingplan was written up to detect any deterioration and to organizethe steps to be taken in the intervention. The position of themetal strips was traced onto a PVC film, as well as the areasfound with beads missing, loose beads, and loose bits of putty.

The window had been tightly wrapped with an adhesivevinyl-like film when it came to our workbench, which provedto be an effective emergency measure in avoiding the move-ment of the fractured glass pieces and the loss of detachedbeads.

The panel was moved to the workbench and positionedlaying flat on the base glass. The vinyl film adhering to theupper side was removed as well as the original edge sealingpaper.

Fig. 1. Window before conservation. Fig. 3. Loose blue beads at the bottom of the window.

e71J. Bonet / Journal of Cultural Heritage 9 (2008) e69ee72

The broken cover glass was removed bit by bit and glass chipswere also separated from the glass bead layer, until all the brokencover glass was removed. Putty bits and loose beads wereremoved (Fig. 2). The adhesion of the beads and metal strips wastested with a soft thin brush. Only some particles placed in areasbordering empty spaces were unstable and prone to come off.Loose glass particles were picked up using tweezers (Fig. 3).Collected beads and chips of crushed glass were washed withwarm deionised water at 60 �C and filtered. The water that ran offthe beads turned pale yellow. The process was repeated until thesolvent did not show any discolouration. The particles wereseparated by colour with the help of a thin brush undera magnifying lens. Most loose particles were 0.7 mm blue beadsplaced at the bottom of the window. The remaining putty stilladhering to the glass edge was removed with a scalpel. The endsof the fracture in the base glass were visible at this stage and wereglued using Araldite 2020 epoxy resin. When dry, a 4 mm pinewood strip was set on the edge of the base glass to replace putty.Putty does not work as a distancer and has a tendency to shrink

Fig. 2. Removal of the broken cover glass.

irregularly so, as the glass bead layer was not completely flat,a safe rigid stopper was needed to prevent any pressure from thecover glass on the glass bead layer. As a rule, it is difficult toremove putty when it is hard and well-adhered, so it may bedifficult to carry out future conservation work on the panel. Theglass particles layer varied more than 1 mm in thickness.

The previously washed and sorted colours were then usedto refill the empty areas (Fig. 4) and the particles were placedon the glass sheet with a manually modified coffee spoon,made by narrowing its shape and cutting off the front end.Then they were glued by placing a drop of fish glue witha needle-free syringe. An area of about one square centimetrewas covered on each replacement, and not until the glue wascompletely dried did we continue with the process. The gluedrying process took 8 h at room temperature. Fortunately thecollected beads were enough to refill all the empty areas.

The conservationerestoration of the broken front glass wasconsidered. The option was dismissed since the gluing of theglass may have caused a distortion that would have been too

Fig. 4. Refilled area with the collected beads.

e72 J. Bonet / Journal of Cultural Heritage 9 (2008) e69ee72

clear and the glass sheet had to provide regular strength andsupport that glue cannot ensure. A 3 mm glass was cut andplaced over the window, and laid on the wood strip.

The panel was, at that point, lifted off the bench and placedleaning on its wider side, thus showing the other side wherethe vinyl film was still adhered. The remaining film wasremoved and the whole length of the fracture was glued withthe same epoxy resin. Finally the edge of the whole windowwas sealed with glued paper.

4. Conclusions

The aspect of the window is very much the same as it was whenVidal Puig manufactured and sold it but this particular methodemployed also has its limitations. Conservationerestoration ofcloisonne panels by the described process is certainly time-consuming but much less so than dismantling the whole piece andalso less ethically questionable. The few windows preservedusing this technique will probably soon require further conser-vation. For this reason a concise bibliography on any of the fewrestorations that have been performed on this type of glazingwould help to inform others about what, in line with modernconservation standards, should or should not be done.

References

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vitrail catalan du XIXe siecle, Techniques du vitrail au XIXe siecle,

Forum pour la conservation et la restauration des vitraux, Namur, 14e17

juin 2007.

[2] M.G. Martın, Les vidrieres cloisonne de Barcelona, Exhibition Catalog,

Barcelona, 1985.

[3] M.G. Martın, Vidrieres d’un gran jardı de vidres, Barcelona, 1981.

[4] J. Vila Grau, Le vitrail cloisonne, Tehnique et science, Les arts du verre,

Actes du colloque de Namur, 20e21 octobre 1989.

[5] S. Strobl, Painting with beads e the work of the London Cloisonne Glass

Company, Techniques du vitrail au XIXe siecle, Techniques du vitrail au

XIXe siecle, Forum pour la conservation et la restauration des vitraux,

Namur, 14e17 juin, 2007.

[6] Cloisonne, Catalogue, The Cloisonne Glass Company, London, 1905.

[7] M. Doerner, Los Materiales de Pintura y Su Empleo En El Arte, Reverte,

Buenos Aires, 1972.

[8] M.C. Triboulot, N. Boucher, The restoration of old wood furniture

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Holzforschung und Holzverwertung, No. 4, 1996.

[9] CVMA Guidelines for the Conservation and Restoration of Stained

Glass, second ed., Nuremberg 2004, The Journal of Stained Glass, vol.

XXVIII, 2004.

[10] S. Mu~noz Vi~nas, Teorıa contemporanea de la Restauracion, Sıntesis

Patrimonio cultural, 2003.

[11] D. Halse, The restoration of the cloisonne glass window at Durban Girls

College, Typescript (2000).