(definitions from Dictionary.com)
35. Glassmaking and Ceramics. a. to coat (plain glass or a glass or
ceramic object) with a layer of colored, opalescent, or white glass. b. to
apply (such a layer). c. to color or make (glass) opaque by reheating.
This sounds like a process. Some people, I hear, barely revise
their flashes. They came out fully baked. Many come out half-baked. Go find an
old flash and revise it. Reheat it. Color it. Make it gleam.