weberceramics Posted November 30, 2023 Report Share Posted November 30, 2023 Hello! I am in need of some advice. I will attach photos. A whole batch of my platters came out with a hairline crack directly going through the center. There is no cracks in the green ware/bisque ware stage but they sometime come out like this. Is this from the clear glaze? Is it cooling too fast? Quote Link to comment Share on other sites More sharing options...
neilestrick Posted December 1, 2023 Report Share Posted December 1, 2023 @weberceramicsCould you post some more pictures? I'm not entirely sure what I'm looking at here in terms of what part of the platter this is- top or bottom, is the ring in the middle unglazed, what's the space between the rings, etc? Quote Link to comment Share on other sites More sharing options...
weberceramics Posted December 1, 2023 Author Report Share Posted December 1, 2023 5 minutes ago, neilestrick said: @weberceramicsCould you post some more pictures? I'm not entirely sure what I'm looking at here in terms of what part of the platter this is- top or bottom, is the ring in the middle unglazed, what's the space between the rings, etc? It goes from the top to the bottom, the ring is unglazed. this is a slab platter where I attached a slab ring to the back Quote Link to comment Share on other sites More sharing options...
neilestrick Posted December 1, 2023 Report Share Posted December 1, 2023 Thanks. The angle and lighting of the photo was playing tricks on my eyes. I would say that the size of the ring is at least partially to blame. It's adding a lot of mass to the bottom so you have a wide thin platter with a thick area at the bottom. Clay prefers to be evenly thick throughout. There would be far less stress on the piece if the foot ring was much less bulky, like 1/4" to 3/8" thick. Also be sure you're attaching the ring when the slab and ring are at similar moisture level. It's also possible that the platter cracked or was at least stressed at the lip before it ever went into a kiln, and finally opened up in the glaze firing. But because the crack extends all the way into the foot ring it's probably because of the added mass there. Callie Beller Diesel and rox54 2 Quote Link to comment Share on other sites More sharing options...
Babs Posted December 1, 2023 Report Share Posted December 1, 2023 I am seeing the non glazed ring as a carved out ring to which the maker attaches a pedestal after the firing. Is that correct? If this is occurring in other platters, I would flick them on coming out of thr bisque firing to hear if they ring or thunk, ping or pung. The unevenness of thickness of clay. Proximity to kiln elements. Unevenness is in drying? Beuatiful onglaze decoration! Quote Link to comment Share on other sites More sharing options...
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