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Cracking Prevention


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#1 GA_Clayman67

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Posted 02 December 2012 - 11:54 AM

Back into the clay after 37-years away and I'm having what has to be a simple problem, but I'm flummoxed!

Making very basic business card holders from slabs. I'm draping the cut piece of clay over a plastic covered 2x4 and letting it sit for 24-hours - also covered. Then, removing the plastic and allowing the pieces to dry on the 2x4.

My problem: nearly all the pieces are cracked after the second day and unusable.

What can I do to prevent this?

Many thanks in advance!

Art Carlson

#2 bciskepottery

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Posted 02 December 2012 - 11:59 AM

Your clay is shrinking against the rigid form. You need to remove them from the form sooner and be allowed to dry on their own.

#3 GA_Clayman67

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Posted 02 December 2012 - 12:01 PM

Your clay is shrinking against the rigid form. You need to remove them from the form sooner and be allowed to dry on their own.



Thanks - makes perfect sense.

#4 Marcia Selsor

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Posted 02 December 2012 - 12:43 PM

Or you could work within a negative right angle. When using wood forms, try sprinkling bal clay or corn starch on the surface to eliminate the clay from sticking to a rigid form. I use newsprint paper between clay and forms when necessary. The link is definitely overkill for business card size, but you will get the idea.


http://ceramicartsda...amic-sculpture/

Marcia

#5 GA_Clayman67

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Posted 02 December 2012 - 02:11 PM

Or you could work within a negative right angle. When using wood forms, try sprinkling bal clay or corn starch on the surface to eliminate the clay from sticking to a rigid form. I use newsprint paper between clay and forms when necessary. The link is definitely overkill for business card size, but you will get the idea.


http://ceramicartsda...amic-sculpture/

Marcia


Thank you! I like the idea of corn starch - will try that next time around.

#6 weeble

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Posted 03 December 2012 - 03:59 AM

IF you're draping around two corners, it won't work because the clay is shrinking as it dries and the board is not. If just around one corner, you could get away with putting something between the form and the clay so its not stuck to the form as it dries. My current go-to favorite is an old paper towel, but if I'm drying slowly a piece of saran wrap works just fine as long as I cover both sides
Maryjane Carlson

Whistling Fish Pottery

#7 GA_Clayman67

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Posted 05 December 2012 - 03:12 PM

IF you're draping around two corners, it won't work because the clay is shrinking as it dries and the board is not. If just around one corner, you could get away with putting something between the form and the clay so its not stuck to the form as it dries. My current go-to favorite is an old paper towel, but if I'm drying slowly a piece of saran wrap works just fine as long as I cover both sides



Maryjane...

thanks... Saran Wrap's a real pain - delighted to hear a paper towel works as well!

#8 weeble

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Posted 06 December 2012 - 02:09 AM

Yep, just be sure to get CHEAP paper towels... I ran into some of the spendy ones that have some sort of softener in the paper that actually left marks on the fired piece. VERY strange, almost like a series of very fine wax resist dots anywhere they were in contact with the clay, even after the bisque. Would have been great if that was what I was looking for, but they wouldn't take the terra sig I was TRYING to apply.
Maryjane Carlson

Whistling Fish Pottery




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