Materials for stained glass windows in catalonian documentation (14th and 15th centuries)

Abstract

During the 14th and 15th century, many churches and palaces for civil institutions were built in Catalonia. These constructions generated a rich set of documents which have been partially preserved. These documents have become an indispensable instrument to allow us to understand the material aspects of this period. The stained glass windows, being an essential element of the gothic aesthetics, are far from absent. In the texts which have been preserved, such as notary protocols, official documents of civil power – Town Council, Royal Palaces, Commercial Institutions – or written documents deriving from accounting institutions, we found amongst many other pieces of information, notes referring to the materials used to make or repair stained glass windows. However, the explanations given are not normally very enlightening and thus it is necessary to put together both the information obtained and the technical process of this period with our present-day knowledge of these materials. Only this way, we are able to interpret the meaning of these texts and understand the use of these materials. We found documents which refer to payments for various tools (pliers, grozing tools, soldering bars, tin and gloves) and materials (plaster, lead, tin, glass, iron fittings, woodwork). Also, some documents mention the purchase of coal, which was used as fuel for the muffle furnaces, or other curious materials such as bleach to clean the glass. The purchase of a brass thread to be used to weave protection nets for the stained glass windows, iron rings and bars to build the metal frames and wood to mount scaffolding are also mentioned. Some indications are very vague, like the purchase of linseed oil, lead carbonate, white lead, resin and plaster. The fact that these materials are mentioned as reinforcement for the windows makes us reconsider questions such as the application of putty during medieval times. The use of putty to cement the leaded panels is not mentioned in Teófilo's teatrise “De Diversus Artibus” (written in the 12th), but our documents and Antonio de Pisa's treatise were written in the same time and both make a minor reference about the putty [Theophilus, De Diversis Artibus, The Various Arts, Thomas Nelsonaud Sons Ltd., Londres, 1961, pp. 36–60; R. Bruck, Die Elsessische Glassmalerei, Strassburg, 1901, pp. 1–12; Der tractat des Meisters Antonio von Pisa über die Glasmalerei, Repertorium für Kunstwissenschaft, vol. XXV, 1902, pp. 240–269; S. Pezzerella, Il trattato di Antonio da Pisa sulla fabricazione dele vetrate artistiche, Perugia, 1976; A. de Pise, L'art du vitrail vers 1400, Éditions du CTHS, París, 2008]. Other references are much more precise, such as the explanation of the use of ceruse to cut the glass. This material was used to outline the place where the glass needed to be cut to reinforce the heat effect of the red-hot iron and allow for a clear cut. When it comes to the purchasing of glass, we find that Barcelona is indicated as the provenance source for this material. The city stands out as an important commercial site for materials being imported from other places. Yet, the existence of an important local production of flat glass it is also made clear in the documentation. The glass furnaces of Bigues, in Vilafranca, and the one in Barcelona city, situated in the Viladalls area (located in the present day around the “Plaça Reial”) are directly named as production sites for glass. The analysis of an important amount of documents, brought to light from different Catalonian archives, informing about technical elements and materials related to the production of stained glass windows provides us with significant and sufficient examples to have a deeper knowledge of the production process of stained glass windows during medieval times.