H Rebecca.  In one of the books i own, i don't remember which, an artist claims that copper sheet will grow with each firing.  I think the author believes that both her glass and her copper expand with the rise in temperature of the kiln, but then the glass cools  first preventing the copper from returning to the original size, hence the copper is stretched each firing.  I do not have personal experience with that, but it would be easy to test.  

I recomend the thompson liquid form in combination with sifting for the back.  this gives you a good thick coat for the counter and you can sift the front for the same firing so both sides are more even.  Less firescale etc.   

Hi there

I am having a problem with my larger tiles warping (5"x5" and 6"x6"). I am using 3 separate coats of counter enamel to begin and then enameling the front of the tile. I am using a Paragon Firefly kiln and firing at 1400 with both leaded and non lead bearing enamels. I am also using a cast-iron iron to flatten when it comes out of the kiln but with not much success.

Any suggestions would be much appreciated ♥

Thank-you

Rebecca