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Hi All
My problem is with making what I call dots, or small round cabochons (up to 10mm). I am making them by cutting a 10mm square piece of 3mm glass and full fusing to a round cab.
Using Bullseye 90 glass and firing on BE kiln paper.
The transparents work fine, but opalescents all pick up the paper or kiln wash.
Because they are so small the thought of grinding or sandblasting them and fire polishing is a nightmare.
I have seen these done many places, but can't find how I can make them with opalescent glass to get the rich colours.
Can anybody help with some hints?

Jeff,
Opal glass tends to stick much more than transparent does to ThinFIre or kiln wash when fired to a full fuse. You'll have much better luck firing the opal squares on a FRESHLY-WASHED kiln shelf. And, in our experiences here at Vitrum Studio, it is important (and well-worth the effort) to scrape and rewash the kiln shelf after every full fuse firing to prevent the next full fuse firing from sticking. I hope this helps!

Thanks Judith. I will definitely try the fresh kiln washed shelf.

You didn't say what your firing schedule was, but you may be firing higher than you need to. Fresh kiln wash or not, the higher you fire the greater the chance some will stick. You want to fire as low as you can to get the results you want, even if you have to extend the hold time out to compensate for the lower temperature.

Mike

Toss those little guys into a bowl of white vinegar for a half-hour or so, then rinse in a small-mesh colander.

I'd advise you to toss the bad ones out...if even one is not completely free of fibre it will be a flaw in your final piece!!
Kilnwashed shelf as suggested is the solution. Full fuse 1480 with 20 min. hold should work fine.

Mike and Don, they were fired at 790 C (1454 F) for just 10 minutes. Most rounded nicely, a couple still were slightly square. This is assuming my kiln temp is accurate. Maybe I should try and have it checked.

Valerie, I will try that vinegar to clean them as well. I had cleaned them quite well by soaking and them scrubbing, but it still left a dull milky surface. Maybe the vinegar will do a better job.

Thank you all for your help.

I toss mine in the tumbler with fine grit for a day or two, which has the added value of rounding the bottoms a bit. Completely cleans off any residual kilnwash/fiber and the milky/dullness (which may be mild devit), knocks off any edges, and lets me either firepolish in the kiln to a full gloss or take them through the rest of the tumbler cycle to a full polish.

If you don't have too many, put a piece of sponge/toweling on a board, wrap a piece of 200-grit wet-dry sandpaper on top of that and secure it. Then push your frit balls across it three or four times. Usually gets all the stuck kilnwash off.

Hi Cynthia
The tumbler idea is very timely as we just purchased a small one. I thought of using that but assumed it would be too rough for the small glass pieces.
What grit and media are you using in the tumbler?

Hi Jeff,
You may also try fusing your dots using irid glass face down. This may prevent the kiln wash or thin fire from sticking to the glass. Irid glass seem to release much better than non irid glass. That may be the simplest way of accomplishing the task.