Crowknows

Hi Had two stoneware electric kiln glaze fires this week. Both using clays and glazes I've used before. Dark blue or black particles have appeared on some pots. Inside and out. On different shelves. Some shelves only one pot affected. Some none. Definitely airborne by the way it has landed on different parts. Seems honeycomb in texture. I hoovered the kiln before firing. I used a clear glaze over underglazes and slip. A white glaze with cobalt oxide over. And some over glazes applied on unfired clear or white glaze. I thought it was the cobalt after the first firing but the second firing they weren't affected. Any advice or ideas would be greatly appreciated. Thanks.

Hi. I have an old pottery craft p5976 kiln with an old temperature control that just shows temp and shuts off at set temperature (or used to). Can I simply get a better controller which will control ramps or will my kiln need to be altered? If I can does anyone know which ones I can use? Grateful for any advice.