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Tips Needed For Using A Press Mould


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#1 Chilly

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Posted 02 February 2014 - 04:17 AM

I'm now onto Mark II of a press mould (I broke Mark I three times), but I'm having a problem with the clay.

 

It's terracotta, and I have no idea of it's make or where it came from or anything about it, other than it was given to me last summer, rock solid, in a small dustbin.  When I got it home I topped the bin up with water and left it.  It's now very wet, so I've dug some out and left it on a load of wooden throwing bats to dry out.

 

If I let it dry too much, I can't work it.  If it's anything less dry it's the stickiest stuff I've ever come across.  It sticks to everything except my press-mould.  It sticks to me so much I have trouble squishing it into the mould.  I don't want to let it dry too much as the mould is casting plaster and I don't want to break another one, although this is three times thicker than the original.

 

I'd be grateful for any tips as to what I can do with this clay to stop it sticking to me.  It's so bad I've had to knead/wedge it wrapped in a cloth.

 

For info, here is a picture of the mould, I spent a whole day carving it, which is something I'd never done before, so feeling quite pleased with the result.  The deepest surfaces are not very level, but the end result can be flatten with a bit of wet'n'dry, and the results are good.

 

 

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Ann

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#2 Evelyne Schoenmann

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Posted 02 February 2014 - 06:42 AM

Are you sure it is clay and only clay you're dealing with? Since you don't know of it's make, can it be possible that it isn't clay at all? Try to wedge/knead some fine sand or other (fine) grog into the clay to take away some stickiness. I like your carving! Evelyne


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#3 Mart

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Posted 07 February 2014 - 01:55 PM

If it was sticking to your mould too, you be in real trouble. :)

Before you waste too much time with this "clay", test fire a small piece of this stuff in a bowl. If it melts, it can not ruin your kiln shelves.

BTW, someone's free crap can cost you your kiln.

LOL, what if it's not terracotta at all but a red iron oxide rich glaze? If so, this will be one of those o_O moments. 

#4 Chilly

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Posted 08 February 2014 - 03:47 AM

If it was sticking to your mould too, you be in real trouble. :)

Before you waste too much time with this "clay", test fire a small piece of this stuff in a bowl. If it melts, it can not ruin your kiln shelves.

BTW, someone's free crap can cost you your kiln.

LOL, what if it's not terracotta at all but a red iron oxide rich glaze? If so, this will me one of those o_O moments. 

 

 

Uuurrrrgh.  Odd you should say that. There is some really red/magenta gloopy stuff at the bottom of the bucket.  When it was given to me, the solid lumps resembled blocks of clay, with the crease marks you get from the plastic wrapping, so I don't think it is glaze. :unsure:  

 

Six of the coasters went into the kiln on Thursday, and there's no class again for two weeks. :unsure:   That might be another shelf I have to fix.  Before I went to this class, none of the shelves had batt wash on them.  At least now they almost all have.

 

I found some other "still in the original bag" terracotta that I opened while teaching at a school, so I know it is clay. Although a lighter colour it was only a little less sticky. There's a dozen of these in the kiln too.  Can't wait..........

 

Wonder if they've been freeze/thawed too many times?


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#5 mregecko

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Posted 08 February 2014 - 11:36 AM

Could it have been turned into a slip at some point? Residual sodium silicate might affect the consistency.




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