Quote:
Originally Posted by Talonst
Flame annealing is also what is being done when you see Vittorio or Lucio working on soft glass sculptures. This is the working one end - to the other method Maui is describing. Here the work proceeds in one direction and the residual heat is slowly moved away from the area that was last worked allowing the piece to remain between the strain and softening points for a while so that the molecules can move without the piece distorting resulting is removal of most of the stress. In many cases the final piece is annealed but even then the annealing usually takes place at lower temps and for less time that would be ideal so as to preserve the form and prevent slumping.
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Talonst, I have to disagree with most of what you are saying but perhaps it's mostly semantics with the term "flame anneal". However, having been working in Lucio's studio for a week earlier this year, I can tell you that the above is not true. There is no effort to ensure that the part that was just worked on stays warm and that the heat moves slowly out of it. Once you are finished with an area, you can move completely away from it without ensuring it stays warm for any period of time. The work gets annealed at soft glass temps for the standard amount of time after the sculpture is completed. It's not considered to have any sort of head start on annealing based on the method of construction.
Scientific glass blowers are not using soft glass so their rules differ quite a bit re: annealing.
I agree you can reduce the stress in glass by using your flame to ensure the heat leaves the piece as slowly as possible but I don't think you can consider that annealing.