Glasswork - the Scientia Review

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Water is the most primary mechanism of decomposition. It forms a number of acidic solutions with ease and without special conditions. The resultant mild acids withdraw alkali from the silica structure of the glass. The removal of this substance renders the core material weak, but also harms the surface; at the surface, alkaline compounds actually retain water and catalyze the degradation process. When glass reaches this state, the surface often feels slippery, and this effect is referred to as weeping. The alkali removal causes visible cracks to develop which account for a cloudy appearance. Heightened alkali withdrawal results in flaking. Extreme thermal fluctuation also poses a threat by creating forces between the glaze and base of a glass, often separating these adjacent layers. 17
History of Leaded Glass The use of lead additives in glassmaking originates in Mesopotamia, which scholars generally agree upon as the origin of the glass craft. Recipes for lead-based glass have been found inscribed upon Mesopotamian in addition to actual colored fragments. Interestingly, recovered shards display a relatively low amount of lead, and it is possible that in some case the inclusion of lead was entirely accidental or experimental. Ancient lead glass discovered in China is much newer and suggests that practice is not as deeply rooted. Medieval glassworkers added Lead compounds intentionally in the greatest amounts; these substances proved well suited not only for painting stained glass but also for integral pigmentation. 18
Page 1: The Art of Glasswork By CHRIS STARB
Page 13 and 14: All processes begin with an anneale
Page 15 and 16: Chemistry of Color Each chemical us
Page 17: Preservation The breakdown of glass
Page 21 and 22: Chemistry of Leaded Glass Lead oxid
Page 23 and 24: About the Authors Chris Starbard is

Glasswork - the Scientia Review

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