Hand crafted containers for caudiciform and bonsai enthusiasts
Monday, April 12, 2010
Disappointment
After many hours and effort this is the result. This 18" oval cracked horribly....but why? having sharp edges along the fissures I'm guessing the damage occurred on the cool down.
Yes, I would aggree with friction, but combined with rapid cooling. Looks like this is the bottom shelf? I don't put flat larger objects on the bottom... been there done that. :( Rather than loose sand or pebbles, I recommend a good shelf grinding (with power grinder) and fresh kiln wash. Also, I had a kiln this diameter... ended up putting a ceramic blanket around the body to keep it from cooling too fast. I too keep adding to my list of what not to do... :) The next one will be fantastic!
Sorry about the cracks. I use light dusting of porcelain sand under flat pieces to minimize friction, it has worked up to cone 10 reduction firings for me with very large flat platters, 10 x 13 and wall plaques 21 x 8 inches. I tried bisquets, but sometimes with porcelain pieces the clay slumped so I went to the sand. And I tried not to put pieces in the hotest part of the kiln and gave them lots of air space around them for quicker cool down.
6 comments:
Wow! That's pretty bad cracking.
Is the piece set directly on the shelf?
The friction can cause cracking... but that looks just short of explosive.
Yes friction is the culprit. Try to fire it either on a bed of sand (lose sprinkling) or on top of small bisque marbles to decrease friction.
Yes, I would aggree with friction, but combined with rapid cooling. Looks like this is the bottom shelf? I don't put flat larger objects on the bottom... been there done that. :( Rather than loose sand or pebbles, I recommend a good shelf grinding (with power grinder) and fresh kiln wash. Also, I had a kiln this diameter... ended up putting a ceramic blanket around the body to keep it from cooling too fast. I too keep adding to my list of what not to do... :) The next one will be fantastic!
Sorry about the cracks. I use light dusting of porcelain sand under flat pieces to minimize friction, it has worked up to cone 10 reduction firings for me with very large flat platters, 10 x 13 and wall plaques 21 x 8 inches. I tried bisquets, but sometimes with porcelain pieces the clay slumped so I went to the sand. And I tried not to put pieces in the hotest part of the kiln and gave them lots of air space around them for quicker cool down.
But it has fabulous drainage! Who's going to see the bottom of the pot anyway?
JoEllen
Opps, looked at the picture again and I see I was misreading it. I see the problem...
JoEllen
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