One mixture for this purpose included 'fat earth' (terra pinguis), Windsor loam, sand, iron filings or powdered glass, and cow's hair. The earthen and glass vessels commonly employed in these processes were very vulnerable to cracking, both on heating and on cooling one way of protecting them was by coating the vessels with lute and allowing it to set. The Alchemist’s Experiment Takes Fire, Hendrick Heerschop, 1687 ( Chemical Heritage Foundation) Lute was commonly used in distillation, which required airtight vessels and connectors to ensure that no vapours were lost thus it was employed by chemists and alchemists, the latter being known to refer to it as ' lutum sapientiae' or the ' lute of Wisdom'. The edges being joined might be scored or cross-hatched to promote adhesion, but clay and water are the only materials used. Large objects are often built up in this way, for example the figures of the Terracotta Army in ancient China. In pottery, luting is a technique for joining pieces of unfired leather-hard clay together, using a wet clay slip or slurry as adhesive. Lutation was thus the act of 'cementing vessels with lute'. Lute (from Latin Lutum, meaning mud, clay etc.) was a substance used to seal and affix apparatus employed in chemistry and alchemy, and to protect component vessels against heat damage by fire it was also used to line furnaces. Soldier from the Terracotta Army, made of several parts luted together before firing

Substance alchemist fix seams