beva wrote:Yes, float. What's that? I've tried to google it, but nothing found.
Can I avoid that by higher process temp?
Eva
Float glass is formed while floating on a bed of molten tin. This tin leaves an invisible coating that has several effects when making kiln fired glass. When the tin layer gets compressed, it "blooms" (tin bloom). I have some spherically shaped molds. In that mold, the frosting is uniform over the whole piece. However any mold with a flat spot, will have areas that are not compressed by the slump. So, with float glass, you must place the tin side on the bottom, so it stretches in the slump, instead of compressing. There are numerous work arounds. An overglaze might work.
The tin can react with certain colors and turn them brown. This can be a killer, or an enhancer, depending on the color.
The tin is also a protective layer that is much less sticky to kilnwash or ceramic fibers. Glass fired tin side down comes out much smoother on the bottom than the air side of the glass. This is significant. For years, I wondered why some glass came out with smooth bottoms, and some with rough bottoms. It was the air side yielding the rough surface.
The solutions are easier when you work in the traditional configuration you have chosen, just put the tin side down. I like to reverse paint on float and fire paint side down. So, I have to work with colors that will not be turned to crap by the tin. BTW, Youghiogheny EZ fuse colors are not effected by tin. I tested them all and got no reactions.
To discover which is the tin side, you need a short wave UV light, preferably with a purple filter. The tin side will glow white from direct exposure to the light. The air side will not.