Frit casting in stainless steel mold

[Suzanne Chudnoff]

I made some really nice, thick 2" high abstract stainless steel molds, intending to use them primarily with frit. This is because I have a lot of frit (rather than billet), and most of the mold shapes I made fit inside each other (creating voids) and I'm not sure I can cut billet small enough to get it to flow properly. I have never attempted thick frit castings before in stainless steel molds, and I forgot that using FINE frit would give me less volume, so the 2"s melted down to only 1". Also, I read that using powders to color the clear frit evenly would not work well using Course frit.

The problem I encountered was that as the frit melted down, beads stuck to the fiber paper lining both inside edges and pulled the fiber paper away from the mold, and ruffled the edges inward. I had though I would get nice straight edges, but the ruffled fiber paper actually ruffled the glass. I had no idea what schedule to use with the frit, so I took it up at 400dph to 1375, and held it for 1.5 hours. And of course, annealed it for a 1.5" slab.

Does anyone have any suggestions on how to use frit without this happening? Should I take it up slower, or to a different temperature, or hold it less or more? How can I keep the fiber paper from falling inward as it crawls down the fiber? Does the thickness of the fiber paper affect this? (I'm pretty sure that I used 1/8"). Any help would be greatly appreciated.

[Cheryl]

Don't use fiberpaper. Kiln-wash your stainless steel instead.

[Bert Weiss]

I'm not sure I am picturing how your mold is shaped. Regardless stainless steel shrinks more than glass while they cool together. So, if the mold can hold on to the glass, it will. I am assuming this is why you used the fiber paper lining, as it would mitigate this. You might try using some colloidal alumina rigidizer to stiffen the paper, or use 1/4" blanket instead of paper. If you do this right, it should yield enough to get the glass out, and because you used colloidal alumina instead of colloidal silica, it may not stick to the glass.

I have some stainless steel rings that I use to frit cast float glass. I line them with fiber rope, then fuse. This may not work for your thicker profile. I don't fire hot enough to get flow. I am looking for a thorough tack fuse (which, it turns out, requires a much hotter temperature than I originally guessed).

[Morganica]

Pics? I'm not visualizing this very well.