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Provenance of the glass

Just about all crafts regulations paid meticulous attention to the quality of the materials used. Not only because the quality of the final item was largely dependent on those materials, but also because this was an area where fraud was a potential problem. Customer trust was an important concern to the crafts and guilds. The guilds were always protecting the ‘name and fame’ of their members, not out of an anachronistic preoccupation with honour and prestige, but because it made economic sense²³. In the prescriptions mentioned below, this is apparent from references to the need for open and proper communication with customers/buyers.

With regard to the provenance of the glass used, the Antwerp guild provides particularly specific information. An ordinance from 1470²⁴ indicates that only French glass (‘franche glas’) could be used for stained-glass windows and for the central section of ordinary leaded glass panels. Rhenish glass (‘Rijns’) could, in some cases, be used for the borders. It is particularly apparent from this document and other ordinances (Antwerp 1470, 1472-1488, 1493)²⁵ that different qualities of glass could not be mixed, unless the person commissioning the piece had given explicit permission to do so. Rhenish glass or glass from Hessel could also be used in windows, but only if no other type of glass was used, unless the buyer had given permission to combine (Antwerp, 1470)²⁶. The fact that this stipulation was reiterated on several occasions may be seen as an indication that infringements were common. These quality requirements would appear to be rather logical, as glass staining cannot be performed properly on uneven glass, while in the case of ordinary transparent glazing the translucency and evenness of the glass is of course very important for the perception of daylight and for looking outside. For that matter, it appears from trial records from Bruges dating from 1674²⁷ that French glass was more expensive than so-called ‘Bourgoens’ glass. Bourgoens glass (Rhenish glass?) cost four stivers a foot, compared to six stivers in the case of French glass. We may conclude on this basis that the French glass was of a better quality. It was probably produced in the wide Paris and/or Normandy region²⁸ and was known for its translucent and transparent qualities²⁹. Glass from Lorraine (i.e. the Rhineland) was slightly greener, which probably explains why it was cheaper³⁰. In other words, the guild wanted to make sure that customers received what they had paid for and that no lesser quality glass was used without the customer’s permission.

Some good examples of the use of two different qualities of glass in a single panel are the 16^th century stained-glass windows with a central roundel from the former Saint-Elisabeth Hospital in Lier³¹. The stained roundels are clearly made of high-quality cylinder glass, while the surrounding unstained glass is yellowish-green in colour and produced according to the crown glass method. These non-stained pieces therefore exhibit the typical concentric stripes on the glass surface.

Finally, we were able to ascertain that, towards the end of the 18^th century, a debate was ongoing in the city of Bruges about wholesale and retail buying and selling of glass. Again, quality care, and particularly the provenance of the glass, was an important consideration³².

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∧  Back to topComposition of the window

In the previously mentioned documents from Antwerp (1470³³, 1472-1488³⁴), we also find evidence of the importance that was attached to the design of the lead composition.
A panel could, for example, only be fitted with border glass if this did not interfere with the continuity of the overall lead composition (i.e. left to right, top to bottom). If two panels were placed on top of each other, the top panel could only have a border left, right and top, while the bottom panel could have a border left, right and bottom.
Great care was also taken not to interrupt the lead lines or ‘formen’, as is apparent from a number of documents³⁵. While this was particularly important in geometrical patterns, the motifs in figurative work also had to be consistent.

∧  Back to topCutting of the glass

As regards the cutting of the glass, we find little information in the rules and regulations, except in an Antwerp ordinance dating from 1472-1488, which states that the pieces of glass should be cut straight and be nibbled down carefully, so that they could be set tightly in the lead. The pieces of glass should, after all, not rattle (‘loteren’)³⁶.

∧  Back to topPainting of the glass

The earliest reference to the quality of glass staining is found in an Antwerp ordinance of 1470³⁷. The directive stipulates that glass and glass paint (‘gescrifte’) should be fired sufficiently well so that the paint could not be wiped out.

An ordinance from Ghent dating from 1541³⁸ prescribes that the ‘glassworkers’ (‘ghelaesewerckers’) should not deliver unfired pieces, except as (temporary) gap fillings (‘eenighe stopinghe’) in places where this is not noticeable. The sentence that follows is extremely important in the history of stained-glass window making, as it may well be one of the first references to enamel paint in the Netherlands. It goes as follows: ‘Nobody shall use blue, green or red (enamel) paint to make panels depicting coats of arms that are larger than 1.5 square feet.’ The use of these colours was however permitted for the realisation of panels smaller than 1.5 square feet and for roundels depicting arms, if one was unable to work out the arms by partitioning with lead cames or by graving of the charge in flashed glass.

On the basis of these directives, we may assert that the guild had reservations about the use of glass dyes such as blue enamel and carnation red. Perhaps it felt that the much more intense colours of pot-metal glass were of a better quality than the somewhat less bright enamel paints. Or perhaps the guild was aware that enamel on blank glass was more sensitive to weathering, so that it tried to prevent the use of such paints in larger monumental windows. After all, the application of enamel paint on vessel glass, its colouring effects and its vulnerability to weathering had all been well-documented in the Netherlands since the 15^th century.

Finally, there is an interesting reference in the roll of the masons’ guild of Malines, dating from 1539³⁹. It prohibits stained-glass artists from placing unfired pieces in churches or homes. The text also stipulates that the firing process should not be carried out too fast and that the glass pieces should be sufficiently heated. The entire work should be ‘neat’ (‘schoon’) and the ‘paintings fixed’ (‘pintuere houdende’), i.e. sufficiently vitrified for the paint to have fused with the glass.

In the second half of the 16^th century, no more ordinances appear to have been issued relating to stained-glass production and firing. As we have already pointed out, this was probably due to the fact that the guilds had become less concerned with the techniques of glass staining because most of their members were now glaziers, as this had become the most important market. Certainly the quality of glass staining deteriorated, while the quality of glass cutting and leading remained important to the craft.

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