Search the Community

Hello, I'm new to these forums and would appreciate some help! This isn't a new problem but I still don't know what causes it. On this particular problem piece, I used: Flint Hills "Porcelain" ^5-6 slip made with mason 6308 (Delphinium) mixed with the Flint Hills clay body Amaco HF-9 Clear Glaze. I do an 8-10 hour bisque to ^04; glaze firing is ^5 or ^6. I'm attaching a photo that shows a sample of bubbles that formed all along the edge of this platter. It happens most often on blue underglaze or slip, but I've had the problem with other colors. Sometimes a mug's rim will come out all bubbly and rarely the bubbles are on the main section of the piece. I dip glaze my work and carefully smooth out any pinholes or bubbles - and as far as I can tell, THESE bubbles along the rim are not visible before firing. Everything else in the kiln with this platter came out great! Here's what I've done so far: I've tried other colorants - several blue underglazes from Amaco & Mayco. I tried clay body slip with mason stain. I've tried other clay bodies. I slowed my bisque time to 8-10 hours. Called Amaco, but they weren't able to help. Does this look like out-gassing that didn't complete during bisque? Do larger pieces require longer bisque firings? Do you have a clear glaze recipe or suggestion that might "fix" it? I'm really hoping you all can figure this out - offer some advise or a solution (yes!) Usually it happens on platters that I've spent hours carving (I sgraffito the work) and I'm so frustrated and tired of re-making work - Please, can you offer advise or a solution? Thanks so much! Carol R