GLASS ANALYSIS
In the Medieval Period, glass in Northern and Western Europe was made from Sand, Lime and Plant-ash. The physical properties were decent and is referred to as FOREST GLASS (High Potash = K, Low Sodium = Na). During the first part of the 16ᵗʰ century, the much older glass composition made from Sand, Lime and Seaweed-ash, became available again and is known as SODA-LIME GLASS (Low K, High Na). Even though SODA-LIME GLASS is as old as the Egyptians, it became unavailable due to a lack of access to the raw material of soda after the fall of the Roman Empire.
FOREST GLASS had some disadvantages for being more brittle and less forgiving. SODA-LIME GLASS was better workable and was quickly preferred by artisans. With better properties SODA-LIME GLASS completely replaced FOREST GLASS by the end of the 16ᵗʰ century.
XRF analysis was performed on Katrain at three different independent laboratories, all concluding period specific glass. The artwork contains both FOREST GLASS and SODA-LIME GLASS. This simple fact places Katrain undisputedly in the transition period, as by the 17ᵗʰ century FOREST GLASS was no longer in use.
The most comprehensive analysis to date was performed by Dr. Bruce Kaiser. His intrinsic knowledge of material science brought him to the conclusion that Forest glass and Soda-Lime glass co-exist in this stained glass artwork.
"Pigments and Glasses appear consistent with the time period that this art work was expected to be made"
-- Dr. Bruce Kaiser
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