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the directions say to hold at 1000 for 4 hours. that seems like a very long time. my piece is 6.5" square. how long would you bubble squeeze it for? also, will the other pieces in my kiln load be ok with that kind of soak? or is 4 hours perfectly normal and acceptable?

I decided to just go with the instructions and just set it up with the 4 hour hold.

lorimendenhall wrote:I decided to just go with the instructions and just set it up with the 4 hour hold.

Probably the right thing to do. 4 hours is a very long time -- and it won't hurt any other pieces in the kiln -- I suspect it's so all of the organics in the paper have a chance to burn off cleanly. Might be overkill, but you have to assume the manufacturer has some idea of what they're doing.

Unless they recommend differently, I would bubble soak at 1250 or so for half an hour also.

The 4 hours@ 1000 seems long but I believe it is for the paper to burn out. Use chads so you don't trap air and gasses during this step.
It's been my experience that the manufacturer's schedule is fine for small pieces (refrigerator magnet size), but for large pieces like yours (6.5"), definitely add a bubble squeeze. I hold at 1150 for up to an hour then ramp to full fuse @ 250 per hr. Here's why:
The glass has just gone through a long burnout phase. If you're using chads (and you should!!), at 1150 the glass will begin to settle SLOWLY from the center helping to "squeeze" out air towards the edges. As you ramp up, the chads give way and the edges will come together. The larger and more complicated the paper design, the longer my hold at 1150 (some have been several hours!!!), especially if the paper has "paper doll" like cutouts that could trap air and gasses inside the design.

1150 might seem low to some for a bubble squeeze but the glass, sitting up on chads, will start "slumping" in the middle at that temp acting like a squeegee, forcing the air towards the edge.

Good luck.

thanks Brad and James. I did use little chads in the corners as they recommend. I'll know how it worked out tonight.
just fyi, here is what the directions said, except I changed their 960 to 900 (old directions!)
250/1000/4h
250/1470/15m
999/900/1h
250/200/0

pretty strange that you follow instructions from the mfg at one point and ignore them at another.

they recommended 960 which was the old recommendation for annealing. now that the updated recommendation is 900 I adjusted. that's why I mentioned that the instructions were old : )

Hmmmm.... what are the annealing temperatures for the chemicals in the glassline paper once it is fused to the glass? The glass is no longer strictly one manufacturer's chemistry is it?

Lori, I would anneal at your normal temp. Don't change when you've had success. I use System 96 so everything get annealed at 950. If you use COE 90, anneal at what is recommended for that glass.

The paper used in the glassline paper is just thinfire. The "textured" paper is wrinkled thinfire! Really! I believe the color is just glassline paint.

The whole trick is to avoid bubbles on the way up to full fuse and we've covered that. Coming down from full fuse, just treat the glass as you normally would at your normal annealing temp.

Kevin, you made a good point and I hadn't even thought of that. anywho my glass came out perfectly - no bubbles!

Lori, if you read the document in full, you will see that 516C is still the recommended annealing soak up to and including nine mm. 482C is recommended for thick slabs to save time. Because of the longer soak time at the lower soak temperature, no time is saved for nine mm or less

ohhhhh I have had enamels on glass spontaneously crack a month or more later and had those enamel cracks slowly spider craze over time. What appears now to be perfect may not yet be.
I was not using glassline at the time but..... about what they told you to do regarding their annealing temperatures.

Kevin Midgley wrote:Hmmmm.... what are the annealing temperatures for the chemicals in the glassline paper once it is fused to the glass? The glass is no longer strictly one manufacturer's chemistry is it?

The GLASS is still one manufacturer's chemistry. The enamels are another. It's the same as with any coating on glass or ceramic--if they're compatible, they'll expand and contract together. If they're not, they'll craze or flake, and it won't matter what annealing temperature/rate you use--they're still incompatible.

As for the glass itself, there is no single magical annealing temperature for all soda-lime glass. Bullseye's switch from 960F to 900F was simply moving from one side of the range to the other (primarily, as mentioned, to reduce both annealing time for thicker glass and the chance of inducing stress instead of preventing it). Both work, but if you're, say, casting an 8-inch slab you could save something like 200 hours by using an anneal soak of 900F instead of 960F. If you're doing simple 2- or 3-layer fusing projects, it doesn't really matter.

http://www.bullseyeglass.com/methods-id ... glass.html