Bubble resulting a huge hole - WarmGlass.com

Bubble resulting a huge hole

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Bubble resulting a huge hole

Postby Gerry669 » Sun Mar 13, 2016 6:53 pm

I am at a loss and seeking any thoughts or help with my problem.
This is the second time having the same issue! The "blue" was the first the "green" was the "second"

This is a 12 X 12 inch sheet done in the style of John Ferrando (and others) fusing stringers to a sheet, cutting them into strips, working a design and then fusing the strips to another sheet.
Used Bullseye glass, with a sheet of thinfire shelf paper, i changed out kiln shelves for the second try, it was freshly prepared using Bullseye shelf primer. Put a piece of frit at each corner
It was done in my Paragon GL24, I checked the thermocouple with a second portable thermo....they were both within a few degrees.
Firing schedule
300dph to 1125 hold 15
100dph to 1225 hold 15
9999 to 1490 hold 10
9999 to 900 hold 60
100dph to 700 turn off

Thoughts, help, ideas, comments? all would be appreicated

Brad Walker
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Location: North Carolina, USA

Re: Bubble resulting a huge hole

Postby Brad Walker » Sun Mar 13, 2016 8:18 pm

Too fast from 1225 to 1490. And 1490 is too high, too.

I know there are a lot of schedules that call for full speed from the bubble soak to the top temperature (some of mine included), but anytime you have a relatively large two layer you need to fire slower up to the top temperature to give the air underneath time to escape. 200 dph or so. And to a lower temperature, 30 to 40 degrees lower.

Firing on thinfire may make it worse, too, thinfire gives off a lot of gas when fired.

If you don't want to fire slower, then fire on fiber paper. That also gives the air a way to get out.

I used to think that the kiln shelf was the culprit, but now I believe the speed is a far more significant factor than the shelf.

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Location: Virginia

Re: Bubble resulting a huge hole

Postby B.J. » Mon Mar 14, 2016 9:45 am

Those that reverse engineer someone else's technique and then write an ebook don't necessarily know all there is to know about that technique. You miss out on all the knowledge of the originator....and that's not John Ferrando.

linn keller
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Location: south tx

Re: Bubble resulting a huge hole

Postby linn keller » Wed Mar 16, 2016 8:45 am

well said.
linn in deep deep south texas

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Re: Bubble resulting a huge hole

Postby Gerry669 » Sat Mar 19, 2016 12:11 am


You are probably right about the thinfire, the only way a bubble can form is for some energy to be below the glass, be that trapping air that expands or out gassing of the thinfire.

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