kiln carving float

[bob proulx]

I would like to try my first kiln carving with float glass and am looking for a good schedule, any recommendations would be appreciated.
Bob

[Bert Weiss]

I kiln carve 10mm float with an unconventional schedule. I fire, tin side down at 600 dph to 1365ºF and hold for one hour. The result is good resolution, no dimensional change, fire polished edges, and no devit. If 600 dph is too fast for your kiln, just slow down. The critical step is stopping at 1365 and holding for 1 hour. If I were firing 6mm glass, I think I'd add 20ºF, and If I were doing 3mm glass, I'd shoot myself. Well, I did that once for some cabinet doors. I forget my schedule, it takes more heat. If it were up to me, with the exception of lighting glass, I would never work thinner than 10mm. I fire all float glass up to 12mm thick at 600 dph in my kilns. It always survives the heatup. This may well not work in your kilns.

[bob proulx]

I kiln carve 10mm float with an unconventional schedule. I fire, tin side down at 600 dph to 1365ºF and hold for one hour. The result is good resolution, no dimensional change, fire polished edges, and no devit. If 600 dph is too fast for your kiln, just slow down. The critical step is stopping at 1365 and holding for 1 hour. If I were firing 6mm glass, I think I'd add 20ºF, and If I were doing 3mm glass, I'd shoot myself. Well, I did that once for some cabinet doors. I forget my schedule, it takes more heat. If it were up to me, with the exception of lighting glass, I would never work thinner than 10mm. I fire all float glass up to 12mm thick at 600 dph in my kilns. It always survives the heatup. This may well not work in your kilns.

Thanks Bert,
I was hoping to here from you. I'm surprised You don't stop and hold in the 1140 range and why do you add more heat for thinner glass?
Bob

[Bert Weiss]

I kiln carve 10mm float with an unconventional schedule. I fire, tin side down at 600 dph to 1365ºF and hold for one hour. The result is good resolution, no dimensional change, fire polished edges, and no devit. If 600 dph is too fast for your kiln, just slow down. The critical step is stopping at 1365 and holding for 1 hour. If I were firing 6mm glass, I think I'd add 20ºF, and If I were doing 3mm glass, I'd shoot myself. Well, I did that once for some cabinet doors. I forget my schedule, it takes more heat. If it were up to me, with the exception of lighting glass, I would never work thinner than 10mm. I fire all float glass up to 12mm thick at 600 dph in my kilns. It always survives the heatup. This may well not work in your kilns.

Thanks Bert,
I was hoping to here from you. I'm surprised You don't stop and hold in the 1140 range and why do you add more heat for thinner glass?
Bob

Stopping in the 1140 range is for a bubble squeeze. We are talking about a single piece of glass. If I were fusing in the same firing, I would add an hour at 1140 and then go up to 1420 with a 40 minute soak.

Heavier glass has gravity working for it, pushing downward. Light glass, much less. Consequently it needs more heat before it moves enough. If you stack up several sheets of thin glass, and fuse them, you will find the most bubbles under the top sheet, because there is much less weight pushing it down. This is a nasty annealing challenge.

[bob proulx]

Thanks Bert.
Bob

[Peter Angel]

Bert, could you please share your annealing schedule for the 10mm float?

Peter

[Bert Weiss]

Bert, could you please give us your annealing schedule for the 10mm float?

Peter

My controller is programed from temp to temp over time. In Fahrenheit:
10mm:
drop to 1000 hold 1.2 hours
1000 > 900 take 1.2 hours
900> 700 take .8 hours
700 > 300 take .8 hours

12mm:
drop to 1000 hold 2 hours
1000 > 900 take 2 hours
900> 700 take 1.5 hours
700 > 300 take 1.5 hours

6mm
drop to 1000 hold .6 hours
1000 > 900 take .6 hours
900> 700 take .4 hours
700 > 300 take .4 hours
The 6mm schedule is actually more conservative than my formula calls for.

20 mm
drop to 1000 hold 4.8 hours
1000 > 900 take 4.8 hours
900> 700 take 3.6 hours
700 > 300 take 3.6 hours

These schedules are in logical steps relative to the way I figure them out. If I were programming in either degrees per hour or in Centigrade, I would probably simplify them to round easy numbers. I figured these out with a formula I got from PPG research in the 80's. The formula was for anneal soak time. It had a variable in it. He did not give me the variable. I had to figure that out. If you compare my schedules with Stone, you will find I soak longer at a lower temp. Our elapsed times including soak and drop to around 900ºF are close though.

For Bullseye or Spectrum, you can drop 80ºF. Likewise, you can take Bullseye's recommended schedules and add 80ºF.

[Peter Angel]

Thank you Bert.