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Dalva88

Will it break/crack when firing ?

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Hello,

I just finished modeling some clay for ceramics (it's called Faïence in french, which translates to earthenware in english ?)  and I would like to know if I should hollow it out more or if it might break/crack when firing ?

 

The object (which is a grenade) is about 1 to 1.5 inches thick, and the top isn't hollow at all. ( see it in picture  1 : the circled part is all full mass) 

 

I'm a beginner, bur I worked a long time on this and now I'm starting to panic because it's pretty dry and  I don't know  if I should have hollowed it out more or if after all this work it might break when firing.....

 

Thanks for your help.

grenade.jpg

grenade 2.jpg

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There are two problems:

Uneven thickness can cause cracking while drying.  Keep it covered with plastic so it can dry very (very) slowly.

If it survives, the next problem is the firing.  The solid parts will likely still be damp, even if the surface is dry.  As moisture evaporates from the surface, the moisture left in the thick parts has further and further to travel to escape, and the outer surface is shrinking, making it harder and harder for the moisture to escape.  It is moisture left inside the thick parts of the clay that causes explosions.

When you fire it, take it very slow to 100C, hold it there for some time for the moisture to warm up and evporate, then take the temperature up slowly for another 100C, then fire as normal.  Be warned that if it does explode it could destroy everything on the same shelf, and may even damage pots on other shelves.

Good Luck

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