Frit Casting With Mica/Getting iridescent castings - WarmGlass.com

Frit Casting With Mica/Getting iridescent castings

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Amanda Walker
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Frit Casting With Mica/Getting iridescent castings

Postby Amanda Walker » Fri Jul 01, 2016 10:46 am

Hello All-
I routinely cast rather large pieces (boxes weighing about 750g, about 3x3" square, walls about 1/2" thick) successfully with a top firing temp of 1520 for about 2-3 hours, in a deep open mold (the bottom of the box is the top of the mold). I do this with both billets and frit.I want an iridescent effect on my finished pieces, and that's ROUGH to achieve in casting. I'd like to try adding some mica to frit to get the iridescence, and have read several posts about which Pearl-Ex powders do well in the kiln. However, there's a lot of variation in opinion on top firing temperatures- most advice is that above 1500, the mica disappears. According to most things I've read, it's only the top temp which is an issue for mica, so I shouldn't need to adjust anything else about my successful firing schedule.
Questions:
1.) If anyone has done something like this, what's your experience with an optimal top firing temperature/time for the mica which doesn't affect the quality of the frit casting?
2.) Would it be more effective to mix the frit with the mica, or to paint the sides of the mold with a mica/Glas-Tac mixture before putting in the frit (after all, I only need the mica effect on the outer walls of the box). I worry that if I painted the sides and then the casting came out scummy (as sometimes frit castings do), then I would have to grind the sides and goodbye mica.
3.) Any ideas about how to do this with billet casting?
Any general advice on casting with Pearl-ex, or any mica product, would be appreciated before I leap into experimenting with such large pieces- all the online advice I've been able to find has been about fusing or very small frit castings.

seachange
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Re: Frit Casting With Mica/Getting iridescent castings

Postby seachange » Sat Jul 02, 2016 1:06 am

My very modest experience with mica (fusing, not casting) is that it changes in very disappointing ways on transparent glass depending on the angle of viewing. By this I mean turning from a pleasant color when viewed from the front to muddy browns when viewed from an angle.

The gold colors are nice on black, but i wouldn't call them "irisdescent". You might want to try mica between two layers of clear, to see if it really matches your expectations.

There are interesting dichroic flakes from CBS which I am sure would deserve the name "iridiscent", but cost is an issue.

All the best, seachange

Amanda Walker
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Location: Austin, TX
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Re: Frit Casting With Mica/Getting iridescent castings

Postby Amanda Walker » Sat Jul 02, 2016 8:18 am

Thanks, seachange. I've done a few fusing experiments and like the result... but obviously this is a bigger and hotter project. No help for it but to just see what happens. I've made ugly stuff in failed experiments before and I have no doubt I'll do it again. But I do think I'll stick to gold on black at first, since your comment agrees with a lot of others I've seen.

I use the CBS dichroic extract all the time in fusing (and I've used it for small casts), and it totally rocks, but it is cost-prohibitive to put on a big piece- especially if I'm mixing it with frit. It is just AWESOME when you etch float glass, use the dichro in the etch, and then fuse that.

Kevin Midgley
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Re: Frit Casting With Mica/Getting iridescent castings

Postby Kevin Midgley » Sat Jul 02, 2016 12:03 pm

If you look up postings and the work done by the likes of Ron Coleman, you may discover ways to work much thinner in your work.
Ron would kiln fuse/cast boxes using single layers of glass in carefully controlled firings.
Unfortunately you cannot ask him questions as he passed away but the records he has left leave clues as to how he made them.
Using his methods, you could use your precious dichro more successfully.

Amanda Walker
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Joined: Wed Jul 09, 2014 8:47 pm
Location: Austin, TX
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Re: Frit Casting With Mica/Getting iridescent castings

Postby Amanda Walker » Sat Jul 02, 2016 1:04 pm

Kevin, I'm aware of Ron Coleman's incredible boxes- what an artist. He made them by gluing fused pieces together and encasing them in sand to hold them in position and then fusing them. I've done it using plaster instead of sand and I loved the results (well, I loved the effect, but my piece was not saleable, I don't think)- but it's really, really difficult. I'm definitely going to set time aside at some point to try to master the technique better.

But I do love the chunky look of the cast glass boxes, and I can do more interesting stuff with lost wax than I can with fusing (more interesting to me, anyway). I can get a pretty good result by putting irid glass against the outer edges of the mold and packing the rest tightly with frit, but it's not optimal (obviously, there are problematic aspects to this). Just looking for more ways to get some extra zing into the cast glass.


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