More Bubbles Questions

Ross · Post by **Ross** » Fri Jul 18, 2003 1:47 pm

I'm flat fusing a single layer (1/8 inch) of sys 96, 12 x 12 on fiber paper, that will be draped. The schedule I used is:

600-1465-25
9999-1000-5
600-955-10
400-800-01

Usually works fine... this time I get a 3 inch diameter bubble that is abou 1 1/2 inches high. When I removed the piece, I could see the circumfrence (sp?) of the bubble in the remains of the fiber paper.

I looked at the kiln shelf and it looks fine. I will scrape and recoat just the same.

Any suggestions as to why this happened?

Jerry · Post by **Jerry** » Fri Jul 18, 2003 2:43 pm

You've raised an issue all of us have faced more times than we are typically willing to admit. However, your description pretty well answers it's own question.

I had the same problem some time back and it turned out to be the thin fire, but not for the obvious reasons. I did a lot of flat firing on thin fire and for one firing, I didn't get all the old thinfire off the shelf. The result was a "lump" on the shelf, actually several small ones that were enough to cause a bubble between the thin fire and the back of the glass.

Anytime the bubble shows up there it is usually because there was something wrong on the shelf or you had some sort of contamination on the back of the glass. Fortunately, your's sounds like an easy one to fix. Make sure you have a clean shelf and I'll bet your problems go away.

Jerry

gone · Post by **gone** » Fri Jul 18, 2003 5:59 pm

This is another situation where slowing down can help quite a bit, especially around 1300 and up.

Els

Ross · Post by **Ross** » Wed Jul 23, 2003 8:30 am

OK guys... I used a different shelf... I cleaned it well... used thin fire... slowed down the ramp up from 600/hr to 300/hr and added a stage

300-1000-01
2000-1465-15
9999-1000-5
600-955-10
400-800-01

I still got a tennis ball size bubble!

I would welcome additional suggestions

gone · Post by **gone** » Wed Jul 23, 2003 12:08 pm

Okay, how about skipping the firing altogether by finishing the edges of the glass with a belt sander, diamond hand pads or even wet/dry sandpaper before draping it? You'll get less texture on your glass as well. Double layers are a lot less prone to these kinds of bubbles because of the weight.

Els

Stuart Clayman · Post by **Stuart Clayman** » Wed Jul 23, 2003 12:45 pm

If you are using the new Thin Fire the problem could be the new paper.. it is thinner and denser and on a thin firing bubbles start.. we have gotten arorund it by putting a sheet of 1/8 inch fiber blanket under it which can be used multiple times. There are many great things with the new paper.. but there also is the bubble problem on thin firings....

Stuart

Ross · Post by **Ross** » Wed Jul 23, 2003 2:36 pm

Els... I'm putting some stringer decorations on the single layer before draping.

Stuart... I haven't used the new paper yet.

Jo Holt · Post by **Jo Holt** » Wed Jul 23, 2003 7:53 pm

Ross wrote:OK guys... I used a different shelf... I cleaned it well... used thin fire... slowed down the ramp up from 600/hr to 300/hr and added a stage

300-1000-01
2000-1465-15
9999-1000-5
600-955-10
400-800-01

I still got a tennis ball size bubble!

I would welcome additional suggestions

Ross,

Did you really mean 2000-1465-15? Or 200-1465-15? If you're going fast from 1000 to 1465 you're going to get bubbles I think.

I know every kiln is different, but 1465 seems a bit high for basically one layer.

Try slower from 1000F up and maybe lower top temp.

Good luck!

Jo