small bubbles revisited

[Linda Hassur]

I can't seem to get most glass to fuse perfectly flat. I just made three panels 18 x 6 inches using this schedule: 450 to 1200, soak l hour, 600 to 1475 hold 5 mins, 9999 to 950 hold 30 mins 450 to 850 hold 30 mins. All came out with small "zit" type bubbles. What does it take to get a completely smooth surface. This glass was a BE red swirled with black. Thanks Linda

[Cynthia]

I can't seem to get most glass to fuse perfectly flat. I just made three panels 18 x 6 inches using this schedule: 450 to 1200, soak l hour, 600 to 1475 hold 5 mins, 9999 to 950 hold 30 mins 450 to 850 hold 30 mins. All came out with small "zit" type bubbles. What does it take to get a completely smooth surface. This glass was a BE red swirled with black. Thanks Linda

Where are these zit type bubbles? Are they the little guys that are within a sheet of glass from manufacture or from trapped air between layers?

One of the characteristics of fused glass is that there are bubbles trapped between the glass layers. To decrease the number and size you might want to squeeze ramp between 1150 and 1250 at 50 to 100 dph, then ramp up at 500 dph to your process temp. The glass is soft enough to squeeze out the air, but isn't viscous enough to tack yet during the squeeze phase of the firing. I would be suprised if you could get a completely bubble free fuse under any conditions... Also, if you use double rolled glass or make certain you put the two smoothest sides of your layered sheets together, this will help decrease the amount of air that gets trapped as well.

[gone]

Soaking a bit longer at your top temps will allow the surface to smooth out. You can refire your piece and the little bumps should disappear. It's a good idea to peek to make sure your surface is the way you want it before you start to cool.