The restoration and conservation of cloisonné stained glass is a little known process that requires specific techniques, materials and skills. The stages of this process are very different from the usual ones in stained glass conservation. The fact that there are few objects manufactured and conserved with this technique means that conservation-restoration interventions are few, four in total to the best of the author’s knowledge, so the bibliography is very limited. There is a great need to share the methodology and criteria used and to publish articles with the description and results of the procedures used by the conservators. This article describes the steps taken to preserve a stained glass window.
The restoration focused on minimal intervention, which due to the type of deterioration was a particularly difficult challenge. The stained glass was found by an antique dealer who was able to identify the technique. We assume that the stained glass is the work of Frederic Vidal Puig, the only known Catalan artist who worked with this method between 1899 and 1904.
Keywords: Cloisonné Glass Company,Frederic Vidal Puig; glass beads; Pfister and Barthels; Stained glass; Stained glass
The stained glass windows manufactured in Catalonia from the late nineteenth century to the early twentieth century contribute to the great heritage legacy of the glass industry of this era. These contributions are a sign of the long history of social and cultural growth of this time in this community in a way that is very different from what happened in other parts of Spain.
In the same period there were many stained glass workshops, all of them clearly involved in the principles of improving the technique and artistic content of the glass industry. As a result, novel techniques and procedures such as trichromy, glass bending, engraving and engraving, gilded or brass-coated leads can be seen in some of the stained glass windows of this period. There is still one more procedure to mention, probably the rarest due to the rarity of objects made in this way and the originality of the process and the materials used.
The truth be told, he fell into oblivion and the recovery of his memory was the result of the research work of Professor Manuel García Martín, made internationally known by Joan Vila Grau. Before Garcia Martin’s publications this technique seemed doomed to slow extinction and it was not even remembered how to name the method. Cloisonné can be confused with the procedure called cloisonné enamel, but it is completely different. In the latter, thin metal strips separate the spaces where molten enamel is applied. In the second, metal strips are applied, but no enamel or heat is used.
The patent rights for the production of cloisonne were registered by Pfister and Barthels in 1897 as partners in a company called The Cloisonne Glass company which was located in the City of London, at 40 Berners Street. According to art historians there was another workshop that manufactured the pieces that can be found in Catalonia and that were apprenticed to this first workshop. This was the interior decorator Frederic Vidal i Javelí who in 1898 sent his son, Frederic Vidal Puig (1882-1950) to London to learn the new method. After only 1 year it seems that he had learned enough to build stained glass windows in cloisonné technique in Barcelona. Shortly after returning he began teaching his father’s workers the new technique. However, it seems that after six months they gave up further learning on the grounds that it was too difficult. In 1904 Vidal Puig went to South America where he spent 13 years without taking part in any artistic activity. When he returned to Barcelona he took over the management of his father’s company, but did not return to work with cloisonné. It is taken for granted that any stained glass window preserved in Barcelona was produced by the firm of F.Vidal between 1899 and 1904. Strobl was able to describe the method of construction as follows.
Strobl construction method
A life-size drawing is placed under a glass of the same size. Glass thickness can vary between 6 and 9mm. The metal strips are bent and placed on the drawn lines and glued with gum Arabic. When this structure is fixed and glued, the partitions are filled with the desired glass particles. Once the entire surface is covered, the ground glass and particles are fixed with fish glue. The adhesive is applied hot and with a small portion of potassium dichromate.
In some cases, while the adhesive dries, the two layers are covered with a 3 mm thin glass. The sides of the sandwich can be closed with strips of mastic passed through a grinder to give them the proper thickness or it can be sealed with tinned copper tape. When mastic is used, the edge of the glass is coated with adhesive paper.
In Barcelona the Bertran i Serra collection manufactured by Vidal i Puig survived and was ceded by the family to the Barcelona City Council. Surprisingly, they are not currently on display and there is no news of their state of conservation since they were last exhibited 20 years ago.
Conservation and restoration considerations
Although the author of the patent claims that the cloisonne technique is long-lasting and easy to repair, this claim is far from the truth. The weak nature of the windows is responsible for the difficulty of preserving them, even transportation and storage are difficult tasks when glass particles, metal parts and dry putty are loose.
Organic adhesives such as gum arabic and fish glue make preservation extremely dependent on environmental conditions, especially humidity fluctuations. Fish glue is hygroscopic so that very high humidities can reverse the initial adhesive setting. Sudden changes in humidity or lack of humidity can cause it to become weak and brittle and become less adhesive and cohesive. Furthermore, the different expansion coefficients of the materials used are also responsible for the adhesion losses of the particles. In the conservation and restoration of cloisonné we have to consider that these objects are not only works of art, but that they had to perform a practical function and function as windows, tables, doors, lampshades, etc..
The conservation and restoration of cloisonné panels raises some dilemmas that must be considered. Their weak nature raises the question of whether minimal intervention and reversibility can really provide an answer to a long-term strategy as prioritized by conservation and restoration guidelines. When it comes to cloisonné, minimal intervention on the original materials cannot ensure long-term preservation and yet must be respected. It is essential that when in use the object is kept in a controlled environment and is subject to periodic inspection.
Other cloisonné restorations have separated ground glass and glass beads, washed and separated the colors, and then rebuilt the colored layer on new float glass using silicone to seal the glass ridge instead of putty and to fix the metal strips. Such a drastic approach can reproduce the original appearance and offer stronger adhesion and more durability. But the originality and authenticity of the window is lost.
On the other hand, the use of polymers such as silicone or paraloid can solve adhesion problems but incorporate other problems such as their uncertain reversibility or absolute lack of it, yellowing, compatibility, etc…
Restoration conservators are not only responsible for preserving the appearance of an object but also the choice of materials made by the artists and craftsmen.
A case study
The panel discussed in this article is particularly rare because it is a cloisonné figure. The window shows a figure identified as Sant Antonio. It has suffered various deteriorations and damages, as well as fractures in the base of the glass and in the cover. Fortunately all the metal strips are in their original position. Prior to any action, a detailed work plan was established, detecting the deterioration and establishing the work stages of the intervention. The position of the metal strips was traced on PVC film, as well as areas where there was bead loss, unbonded beads, and loose pieces of putty. The glass had been tightly wrapped in a vinyl-like cling film when it arrived at the workbench which was an effective emergency measure to prevent movement of the fractured parts and loss of loose glass beads.
The panel was moved to the workbench and positioned on the base glass. The self-adhesive film was removed as well as the remains of the perimeter sealing paper.
The broken cover glass was removed piece by piece and the small fragments were separated from the glass beads, until everything was removed. Pieces of putty and loose beads were also removed. The adhesion of the metal particles and strips was tested with a soft, thin brush. Only some particles located at the edges of empty spaces were unstable and easy to detach.
The glass particles were collected using tweezers and washed in deionized water at 60°C and filtered. The cleaning water turned pale yellow. The process was repeated until the water showed no color change. The glass particles were separated into colors with the use of lenses. Most of them corresponded to 0.7 mm glass particles. The remains of putty adhered to the glass were removed with the help of a scalpel. The ends of fractures in the base glass that were visible at this stage were bonded using Araldite 2020. When dry a 4 mm pine lath was fixed to the edge of the glass to replace the putty.
The putty does not work as a separator and has a tendency to shrink unevenly. As the colored layer was not regularly flat a rigid and secure spacer is needed to avoid any pressure from the cover glass on the glass bead layer. In general, it is difficult to remove the putty when it is dry and well adhered, so it can be difficult to perform any conservation task on the panel. The glass particles varied in thickness by more than 1 mm.
The colors previously washed and separated into colors are used to fill in the empty parts that were put in place using a coffee spoon modified for this purpose, narrowing the shape and cutting off the final end. They were then glued by adding drops of fish glue with a needleless syringe. An area of about 3 square centimeters was covered and the process was not continued until it was completely dry. Total drying at room temperature took about 8 hours. Fortunately, the particles collected were sufficient to fill the empty parts. Preservation of the front broken glass was considered but discarded. The gluing of the glass would cause appreciable visual distortion and the glass had to be strong and bear some of the weight in handling the panel. A 3 mm glass was cut and positioned in the stained glass window on the wooden strip. At this point the panel was lifted off the bench and positioned resting on its longer side, thus revealing the other side where the self-adhesive vinyl was still attached. The film was removed from the entire fracture length and consolidated with epoxy adhesive. Finally, the edge of the entire stained glass window was sealed with gummed paper.
The appearance of the stained glass window is very similar to how it was when it was made and sold by Vidal Puig, but this particular method has its limitations. The conservation and restoration of cloisonne panels following this process is indeed time consuming but less time consuming than dismantling the entire stained glass window and less ethically questionable. The few conserved stained glass windows will soon need some treatment, for this reason a concise bibliography of the few existing cases will help others on what, according to modern conservation standards, should or should not be done.
 S. Cañelles, N. Gil, Réintroductions techniques et ”innovations” dans les vitrail catalan du XIXe siècle, Techniques du vitrail au XIXe siècle, Forum pour la conservation et la restauration des vitraux, Namur, 14e17 juin 2007.
 M.G. Martín, Les vidrieres cloisonné de Barcelona, Exhibition Catalog, Barcelona, 1985.
 M.G. Martín, Vidrieres d’un gran jardí de vidres, Barcelona, 1981.
 J. Vila Grau, Le vitrail cloisonné, Tehnique et science, Les arts du verre, Actes du colloque de Namur, 20e21 octobre 1989.
 S. Strobl, Painting with beads and the work of the London Cloisonné Glass Company, Techniques du vitrail au XIXe sie`cle, Techniques du vitrail au XIXe siècle, Forum pour la conservation et la restauration des vitraux, Namur, 14e17 juin, 2007.
 Cloisonné, Catalogue, The Cloisonné Glass Company, London, 1905.
 M. Doerner, Los Materiales de Pintura y Su Empleo En El Arte, Reverte’, Buenos Aires, 1972.
 M.C. Triboulot, N. Boucher, The restoration of old wood furniture marquetry: protein glues, their analysis, upgrading and rehydration, Holzforschung und Holzverwertung, No. 4, 1996.
 CVMA Guidelines for the Conservation and Restoration of Stained Glass, second ed., Nuremberg 2004, The Journal of Stained Glass, vol.XXVIII, 2004.
 S. Muñoz Viñas, Teoría contemporánea de la Restauración, Síntesis Patrimonio cultural, 2003.
 D. Halse, The restoration of the cloisonné glass window at Durban Girls College, Typescript (2000).