All the remarks about annealing, lumps, etc.
"Laboratory Manual of Glass-Blowing"
Francis C. Frary
The loss of strength is the greatest evil in this case; for cast iron, though made for this purpose more tough than usual by careful annealing, is still much weaker than wrought-iron, and serious accidents often arise from harness giving way.
"On the Economy of Machinery and Manufactures"
Charles Babbage
It sometimes happens when the varnish is not very good that by repeated washing the gold wears off; on this account the practice of burning it in is sometimes had recourse to; for this purpose some gold powder is ground with borax, and in this state applied to the clean surface of the glass by a camel hair pencil; when quite dry the glass is put into a stove, heated to about the temperature of an annealing oven, the gum burns off; and the borax, by vitrifying, cements the gold with great firmness to the glass, after which it may be burnished.
"Young's Demonstrative Translation of Scientific Secrets"
Daniel Young