Glaze Drying Crack problem solved
Sept 13, 2016 5:07:43 GMT -6
Post by morgan on Sept 13, 2016 5:07:43 GMT -6
Well... at least it looks that way.
Some of you may remember me going insane trying to figure out why my glaze was Death Valley cracking while drying. To the point of huge chunks losing adhesion. Tried (almost) everything I could think of. DI/RO water, less water in the slurry, thick application, thin application, dipping, spraying, brushing, various bisque temps, wiping ware with a sponge right before glazing, a soaking wash and let it dry completely or not, calcining the zinc, raw and calcined bentonite in various amounts, CMC, V-gum, Epsom Salts, muriatic acid, mixing a bit of toilet paper into the slurry, changing porcelain, using high fire stoneware clay... Still, bad cracks. Some methods better than others, but I was very close to ending my crystalline career. Glazing a load took me the better part of two days. Most of the time was spent trying to repair cracks and get the glaze to stick to the pot.
Made a batch of porcelain pumpkins. Putting the creases in the sides to make it actually look like a pumpkin made the surface rougher than I typically like. A lot rougher. My practice has been to smooth and burnish the surface until it shines while still on the wheel. I spent a while with a greenie smoothing out the rough texture, but still had sanding marks. I noticed those pieces didn't crack during the glaze drying. Hmmmmmmm...
Next load of pots I just got the surface even but no burnishing. When bone dry I went over the whole exterior with a greenie then bisqued.
Glazed the entire load in a morning. Used a couple of new batches of glaze and a couple batches of old glaze that had previously cracked. Other than the sanding everything else remained the same. Brushed on thick, hit it with the heat gun, brushed on more. ZERO drying cracks. I was one happy camper (or potter).
I've been making the clay surface way too smooth and the glaze had nothing to hold onto. Just unloaded the glaze kiln this morning and every pot is awesome. I'm back in the game (albeit with less hair).
Some of you may remember me going insane trying to figure out why my glaze was Death Valley cracking while drying. To the point of huge chunks losing adhesion. Tried (almost) everything I could think of. DI/RO water, less water in the slurry, thick application, thin application, dipping, spraying, brushing, various bisque temps, wiping ware with a sponge right before glazing, a soaking wash and let it dry completely or not, calcining the zinc, raw and calcined bentonite in various amounts, CMC, V-gum, Epsom Salts, muriatic acid, mixing a bit of toilet paper into the slurry, changing porcelain, using high fire stoneware clay... Still, bad cracks. Some methods better than others, but I was very close to ending my crystalline career. Glazing a load took me the better part of two days. Most of the time was spent trying to repair cracks and get the glaze to stick to the pot.
Made a batch of porcelain pumpkins. Putting the creases in the sides to make it actually look like a pumpkin made the surface rougher than I typically like. A lot rougher. My practice has been to smooth and burnish the surface until it shines while still on the wheel. I spent a while with a greenie smoothing out the rough texture, but still had sanding marks. I noticed those pieces didn't crack during the glaze drying. Hmmmmmmm...
Next load of pots I just got the surface even but no burnishing. When bone dry I went over the whole exterior with a greenie then bisqued.
Glazed the entire load in a morning. Used a couple of new batches of glaze and a couple batches of old glaze that had previously cracked. Other than the sanding everything else remained the same. Brushed on thick, hit it with the heat gun, brushed on more. ZERO drying cracks. I was one happy camper (or potter).
I've been making the clay surface way too smooth and the glaze had nothing to hold onto. Just unloaded the glaze kiln this morning and every pot is awesome. I'm back in the game (albeit with less hair).
