Bubbles with powders

lissa · Post by **lissa** » Fri Jun 13, 2003 9:06 pm

I have been fooling around with the world of powders (bullseye) and the other day I did a fire of little test tiles with powders used in all sorts of ways. I used different bonding mediums, different colored sheet glasses, various methods of application and removal, and also played with fusing with powders as top layer, bottom layer, and sandwiched between two layers. My question stems from the last category...I best liked the effect with the powders sandwiched between two pieces of sheet glass, yet in both the test tiles that I did this, a ring of little bubbles formed around the perimeter of the design. I used a super slow schedule to allow bubbles to escape and had no other bubbles in the scores of other tiles. I am wondering what caused these rings of bubbles. On both the tiles like this I used Sprite as my medium, could this be the problem? Also the powers were fairly, but not super, thick. I have done some more involved pieces this way that I am getting ready to fire and would love to avoid the bubble-ring! I am thinking of just firing with the powders as the top layer as I like that option second best, but if anyone has any insights on the matter I'd love to hear em'!

Thanks, lissa.

Tony Smith · Post by **Tony Smith** » Sat Jun 14, 2003 1:53 pm

Lissa,

There is a lot of air trapped around the powder particles... these will not escape during a soak. This is one of the reasons why thick areas of powder usually look cloudy when fused solid. My suggestion would be to use less powder or use the powder on top.

Tony

Cynthia · Post by **Cynthia** » Sat Jun 14, 2003 5:37 pm

I think you need to do it in two firings. First, fire your powder design on the base, then fire again with a cap. Powders (transparents) will still retain a certain opacity because of the amount of air inherently trapped or within the powders, so I don't think you'll be able to fire out that ring in a single firing.

One test you might try though to see if it would work is to use chads placed on the base to support the top layer of glass above the powder layer. Use chads that are the same color as the glass base or the cap, and that are big enough to suspend the cap over the powder. Make sure you place them right at the edge of the glass...one at each corner or three, like a tripod if the piece is round. This might allow much of the air to escape before the cap bends down and seals over the powders. Worth a try at least, eh? Maybe this will eliminate your bubble ring and a second firing.

Good luck

lissa · Post by **lissa** » Sat Jun 14, 2003 7:05 pm

Thanks! Cynthia, that's just what I decided to do, I am going to break it into two firings. Also, in order for the powder design not to distort I need to have the piece at least 1/4" thick for the fuse firing, so in the end the pieces will be three sheets thick rather than just two and will take two firings rather than one. That's a great idea to see what chads will do for it, I'll have to throw a test tile in using that method, if it works it could eliminate not just the second firing but the third layer as well.

Thank you both for your insights, I really appreciate it.

lissa.