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CarolR

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  1. I'm having some problems with bisque firings and would like to run this by you... I use stoneware which I underglaze at leather hard, then I sgraffito the piece. I let it get to bone dry and do the bisque in an old kiln - it has 4 on/off switches; the manual said to flip one switch an hour and then wait till the kiln sitter turns it off (^04). then I apply clear glaze to the cooled work and fire to ^5 using a newer kiln with an electronic controller. Then I started having a problem. After the glaze firing some of my pieces had areas, usually circular, where the it looks like the glaze has pulled away, taking the under glaze with it. So there's a small area, sometimes several all near each other, where the clay body is exposed. In the photo, hopefully you can see the white spots, center right. Because I use their products, I called Amaco for help. I was told my bisque firing was too fast, that out gassing was not complete. And I was told a bisque to ^04 should take 10-12 hours! So now, hearing about these fast bisques, I'm confused. I was an advocate of bisqueing as fast as possible - my little old kiln could fire off in 5 hours. But lately that doesn't seem to be working for me, so I'm going to to do a really slow bisque next time, as Amaco recommends. But why is it that some of you have no problems with a fast bisque? Wouldn't incomplete out gassing affect your glazes? Any thoughts on this? Thanks!
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