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07.11.2019

Mylène Vigneron: Between Tradition and Innovation: Debitus Stained Glass Studio, France

The name ‘Debitus’ is often heard within the stained glass community. While the company is known for its glass paints and patented protective glazing system, less is commonly known about its history and the people behind the production process. Mylène Vigneron, stained glass conservator and graduate from University of York's Stained Glass Conservation and Heritage Management masters programme, reflects on what she learned about Debitus while on work placement.

Background

In 1980, Hervé Debitus founded his stained glass studio in the city centre of Tours, France. He soon began research on the conservation of historic windows, as well as making traditional glass paints in collaboration with the French Laboratoire de Recherche des Monuments Historiques (LRMH).  In 2008 Hervé became a Master of Art, and passed on his knowledge to Laurence Cuzange, who now runs the studio with Nicolas Babouin, a specialist in protective glazing. The studio is internationally recognized for its innovative work, and there was much for me to learn while on placement there.

Innovation and Dedication to the Preservation of Stained Glass

Stained glass windows are fragile and vulnerable heritage. In architectural contexts they may be directly exposed to weathering, pollution, condensation, variations in temperature, and vandalism. This can alter the integrity of the material composition of a window and lead to dramatic consequences even for the building itself. Protection of stained glass windows is therefore crucial to their preservation.

I have come across various protective glazing systems since I began work as a stained glass conservator in 2014. The most commonly used and recommended system is the isothermal protective glazing system, which equalizes environmental conditions on the interior and exterior of the historic glass. This is done by installing the protective glazing in the building envelope and bringing the historic glass to the interior, with airflow between the two. This system can be effective for the longevity of the historic glass, however, an often overlooked consideration is its aesthetic impact on the building's exterior.

fig.1.jpgFig1. Comparison between a single sheet of glass and a thermoformed panel, Sainte Chapelle, North side, Paris, France. Courtesy Laurence Cuzange

Hervé Debitus and the LRMH addressed this issue by creating a protective glazing system with the outside appearance of the historic glass. Hervé Debitus installed his first protective glazing system at Tours Cathedral. His first attempt appeared overly dark due to the colouring patinas, but was successful in that it did not impair light transmission. The final protective glazing system he produced is very subtly coloured, and is barely distinguishable from the historic glass to the average person. The Debitus system is found in many French buildings including the Sainte Chapelle in Paris, Vincennes (castle and chapel), cathedrals of Chartres, Poitiers, Amiens, and Reims, as well as other churches throughout France (Fig.1).

During my placement I was involved in nearly all stages of creating the protective glazing for Bourges Cathedral. The process consists of making a replica of each historic panel in thermoformed sandblasted float glass with applied patinas. The panels for Bourges were made with laminated safety glass, which was also manufactured in the workshop.

For each historic panel, two sheets of float glass are cut to size from a template. My favourite step is the following application of patinas to mimic the glass colours and lead lines of the original panels. The float glass is placed on top of the historic panel on a light box, and the patinas, mixed to a smooth and fluid texture, are then traced onto it.

fig.2.jpgFig2. Mylène Vigneron glazing a thermoformed panel from Bourges Cathedral

Next the exterior impression of each original panel is taken. The float glass for each panel is then placed on the impression and fired at 760°C. Firing takes a full day in order to let the glass anneal to avoid any tension. I helped with unloading the kiln and cleaning the glass before assembling the two sheets into a single laminated panel. To laminate, resin is poured between the two layers of glass. This process requires accuracy, as a precise amount of resin must be poured between the two glass layers or the glass will break. Finally, the panels are glazed with a U-shaped perimeter lead (Fig.2).

In working on each stage of manufacture, I came to understand the complexity and precision that goes into each protective glazing panel. The advantage of this process is it can be adapted to each window and its conservation requirements (Fig.3).

fig.3.jpgFig 3. Historic panel depicting Saint Hervé and its thermoformed panel, Chapelle Saint Hervé, Gourin, Morbihan (56), France. Courtesy Laurence Cuzange

A Return to Traditional Craft: Making the Glass Paint

In the 1990’s, alongside his research for the protective glazing system, Hervé Debitus collaborated with Miss Perez y Jorba of CNRS and the LRMH to recreate glass paints that were no longer produced and whose recipes had been lost over time.

The traditional brown or black glass paint we often see on stained glass is called ‘grisaille’. It is composed of ground lead-based glass and metal oxides. It is mixed with a binding medium and applied to the glass surface and fired around 620°C. Historically glass paint was made by glass painters themselves, but since the decline of glass painting during the 17th and 18th centuries in France, the recipes had been lost. In 1828, The Manufacture Royale of Sèvres near Paris, well known for its ceramics, founded a glass painting workshop where research was carried out to recreate glass paints based on the paints used in the ceramic industry. 1

Later on, the Lacroix & Company, based in Paris, manufactured and sold these glass paints. However, the company stopped producing them when it ceased to be profitable. The LRMH felt the need to create glass paints again based on those old recipes. This research is important for the conservation of stained glass, firstly for understanding the issues encountered with 19th century glass paints, and secondly for making sympathetic and long-lasting painted insertions when required. 

Hervé Debitus was entrusted with this project, and he offered to make a manual with all the recipes to be available to all glass painters. This idea was decided against as it seemed too complex. The other possibility was to have the glass paints made industrially, but since the market is small and limited, it was not possible. Hervé and the LRMH worked then to recreate the recipes themselves (Fig.4)

fig.4.jpgFig 4. Molten grisaille in the crucible. Courtesy Laurence Cuzange

In the Debitus workshop, Laurence now heads glass paint production. The process has remained very traditional and hand-crafted. It requires mixing and grinding a flux and a pigment together. A wide range of coloured grisailles can be obtained this way. Silver stain, copper red, amber, and Jean Cousin are also produced (Fig.5).

fig.5.jpgFig 5. Set of grisaille paints by Hervé Debitus. Courtesy Laurence Cuzange

Conclusion

My experience at Debitus gave me greater insight into the complexity and challenges of this patented protective glazing. It was also gratifying to see the making of the glass paints that I use in my daily practice of stained glass.  I would like to thank Laurence, Nicolas, and Hervé for welcoming me and for sharing their knowledge and expertise.  

1 Brisac Catherine et Alliou Didier, « La peinture sur verre au XIXe siècle dans la Sarthe », Le vitrail au XIXe siècle, Annales de Bretagne et des pays de l'Ouest, 1986, p389-394

Written by Mylène Vigneron, Proofread by Greer Ashman


Do you have your own story to tell? Let me know at cinesta@icon.org.uk!

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