designing & firing a 5 layer project

[Morganica]

Just FYI, Bulleye's posted an interesting tip on reducing bubbles between layers of glass in a stack--basically, sift a little clear powder down on the bottom sheet, top it, and fire with a bubble squeeze: http://www.bullseyeglass.com/methods-id ... power.html

I've done this inadvertently a few times and noticed how bubble-free the glass was, but never really put things together. It's a neat technique, and probably really useful for stacking multiple layers.

On the firepolish, it *is* possible to firepolish a thicker piece of glass without spreading the edges or losing its shape--I do that with small sculptures and cast pendants sometimes. But it's tricky and seems very dependent on the individual piece. Getting a polished edge on a symmetrical 5-layer slab wouldn't be that difficult, but you'd want to watch it very carefully in the kiln and be willing to accept a softened/rounded edge. Theoretically I could fire my larger sculptures that way, too, but the risk of thermal-shocking the glass is high enough that I've never tried it.

BTW, if you're grinding the edges with the standard edge-grinder (like the little spindle kind used for smoothing off sharp edges in stained glass), it may be a little rough to get a full-gloss edge polish without a lot of heatwork. The smoother the finish on your grinding, the less heatwork you'll need to bring up the gloss.

You can start with an edge grinder, then get yourself some wet-dry sandpaper in 220, 400 and 600 grit and an old sponge. Wrap the sandpaper around the sponge, dip it in water, and go to town. It won't take long, and it'll be easier to get the edge without deforming the rest of the glass. (You'll still have to go slow and watch carefully, though)

[Morganica]

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When I'm doing this, I like to overfire slightly, to make sure that the center is as flat as possible. I'm a huge fan of never firing more than I have to, so I'd just leave the other sheets unfired. Then stack them with your prefired sheet, dam it with firepaper, then fire once more.

Cynthia,
What do you mean by 'overfire'?, time-wise? how much more time do you spend, probabley at process temprature.
You do not mean a higher temp. by 'overfire', right?

Thanks,
Havi

Right--I mean just add extra time at the highest temp in the schedule, simply a little extra time to let gravity and surface tension do their work. I might fire a little hotter, but usually I just add 10-15 minutes to process temp.

It's amazing how much contour there is to a flat fuse piece with a lot of decoration (if you want to see how much, just try grinding the top surface of a piece of fused glass until it's perfectly flat--you'll have peaks and valleys all over the place).

[Hedda]

Just FYI, Bulleye's posted an interesting tip on reducing bubbles between layers of glass in a stack--basically, sift a little clear powder down on the bottom sheet, top it, and fire with a bubble squeeze: http://www.bullseyeglass.com/methods-id ... power.html

I've done this inadvertently a few times and noticed how bubble-free the glass was, but never really put things together. It's a neat technique, and probably really useful for stacking multiple layers.

Three years ago, when I learned the basics of fusing at the glass college Gilrafael in Tel Aviv, our teacher Yefim Friedlin taught us to
always sift transparent powder between the layers in order to reduce bubbles. His tehnique involves sifting the powder in an different manner than BE recomandations: a somehow thicker layer on the perimeter of the layer [but still thin], so as to avoid the fusing of the edges preceeding the fusing of the center and to allow the escaping of the eventual air remaining between the layers.
I almost always do this and i never had bubbles between layers, except for the small, "champagne " style ones the BE tip writes about. Of course i had lots of other problems, but the advices and tips HERE helped me overcome most of them.

[Marian]

Thanks for the heads up on this technique for stacking layers.