Frit Casting With Mica/Getting iridescent castings
Posted: 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.
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.