[patienthand]

I have done this for YEARS...

a good tip for the boro workers is.. soot the glass up evenly in the flame you described above, then slowly burn off that soot, it takes you to roughly the annealing temp of boro to burn off the soot, and you can visually see whats hot and whats not by where the soot is burning away, then you can garage it, or if its not too thick you can let it cool in a rack, with no draft and touching nothing and kiln anneal later.

what truly sets you up for cracking is thick and thin glass, and uneven cooling rates... so if you bring it all to a uniform temp and let is cool evenly, assuming its thinner blown work, you are golden till you anneal,, not so much for thick work.