Glass enamel challenge
Uou don’t mention what type of enamel you are using…and in my limited experience there is a huge difference between them, and the results they produce. Also I wasn’t clear from your first post, and it’s initial reply, if you were speaking of heat at F level or C level?
Fuse Master makes some lovely enamels, as does Ferro Sunshine enamels. The Fuse Master line has lower fire (around 1250-1300* F, I believe) and high fire (around 1450-1525* F I believe) so you can plan on painting before slumping with the former and before fusing with the latter. Be sure to work with a painting medium and make some small tests…even finding the brand which works for you does not guarantee that each color in the their line will be consistent. Hope that helps a tad…
Windows listen attentively for the sound of broken glass.