I'm having trouble with the outcome of my glaze firings. None of the pieces that I fire turn out to be the color they are supposed to be, they have pinholes and there are bubbles/blisters in the clay. I'm using Dick Blick Stoneware Clay cone 5-10 and Dick Blick Stoneware Glaze cone 4-7. I'm bisquing at 1940 degrees and glaze firing 2232 degrees. I'm ramping the glaze firing 180 degrees per hour for the first five hours, then 270 degrees per hour for the rest of the firing. If any more information is needed, let me know. Any help will be appreciated.