Sunday, August 5, 2012

A Tale of Two Lidded Jars



I unloaded a bisque today, including several of these single-piece lidded jars, that are thrown as closed cylinders, then cut. One of them cracked in a pinwheel pattern. They always do when I forget one step, but let my error be your learning opportunity!

To prevent these sorts of cracks, after I cut the top off ("and after it's leatherhard...!" interjects Captain Obvious), I turn the lid upside down and trim out a small circle in the middle right where the dimple of the joining occurs. It may be the the trimming compresses the clay just enough, or perhaps it removes little microscopic cracks before they can turn into big ones; what I do know it that the failure rate without that step is pretty much 100%, and trimming stops pretty much all of it.

7 comments:

Barbara Rogers said...

Hi Lori: I never learned that trick, so I'll be so glad to do it the next time I make a lidded box. Thanks.
Barb at Alchemy of Clay

Sue Pariseau Pottery said...

Very interesting tidbit. Thanks. I'll have to remember that.

littlewrenpottery.co.uk said...

Oh dear, shame about the cracking - I always think its the little details that make the difference on a pot

Chuck Billy said...

I think you are right about the compression, I once saw Bill Campbell turn a lid over, and he put a little ball of clay in the center, and pressed it in firmly. Then he stamped his chop there, and he said this helped him avoid those cracks.

Nancy Blokland said...

thanks for that tip. that cracking just ruins a pefectly good piece. That happened to pumpkin pots I did last fall and so didnt make them this time. Oh well, maybe I can do bell type forms for the Christmas sales, now that I know.

Nancy Blokland said...

thanks for that tip. that cracking just ruins a pefectly good piece. That happened to pumpkin pots I did last fall and so didnt make them this time. Oh well, maybe I can do bell type forms for the Christmas sales, now that I know.

Nancy Blokland said...

thanks for that tip. that cracking just ruins a pefectly good piece. That happened to pumpkin pots I did last fall and so didnt make them this time. Oh well, maybe I can do bell type forms for the Christmas sales, now that I know.

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