Blasted Air Bubbles
- October 19, 2011 at 1:10 am #9697Oliveoyl13Participant
I fused two pieces of Spectrum 96 with Glassline paint on the top layer this weekend. I used my standard firing schedule but still wound up with bubbles. My question is will refiring the piece possibly remove the bubbles? Or do I just need to start over?
Thanks in advance for any advice!
OliveOylOctober 19, 2011 at 9:18 am #12271Stephen RichardParticipantOctober 23, 2011 at 10:34 pm #12272Oliveoyl13Participant
The bubbles are small and just under the surface, not burst.
The fusing schedule I use is
300 dph, 1000, hold 2 min; 300 dph, 1150, hold 15 min; 600 dph, 1250, hold 20 min; 600 dph, 1480, hold 20 min; AFAP. 100, hold 60 min; 90 dph, 960, hold 60 min; 120 dph, 750, hold 10 min; 300 dph, 100, hold 0 min.
I let the kiln cool down for about 12 hours after the firing just to be extra cautious.
I am a novice and am not really sure about the bubble squeeze.
OliveOctober 25, 2011 at 9:24 pm #12273Stephen RichardParticipant
In my view you have a complicated firing schedule. A good way of testing your schedule before committing youself to it is to be able to explain the purpose of each step of the schedule. For a fuse firing fo 6 mm thick for me, go at a single rate to the bubble squeeze, soak there for 30 mins and then advance at a quicker rate to the top temperature (trying to get the work done in 10 mins).
The reasons for this – a steady initial heat rise to ensure the glass is all increasing in temp together. the bubble squeeze is to allow as much air out as possible at or near the slump temperature for that glass. The more rapid rise to top temperature is to get through the devitrification range as quickly as possible. [I’ve left out the cool and annealing portions].
A review of the S96 web site will give you information on both the bubble squeeze and temperatures for various processes.
Small, pin head sized bubbles are a feature of kiln formed glass, as they are already in the glass, unlike blown glass. Re firing will not get rid of these bubbles, unless you wanted to go to a high temperature for a long time. And then you would probably ruin the piece.
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