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stellagroov

Can I add unfired clay to fired clay?

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Although I do not generally work at low temperatures, I would say unlikely to be strong enough.   The low fire aspect is the problem.  The way particle bonds are formed in low fire is different from high fire.  If you would have said high fire, no problem.  Grog, which is already fired, is a common addition to stoneware. 

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Probably not because the fresh clay, as it dries prior to firing, will shrink, while the fired clay will not shrink during the drying process. Then when you fire it, the fresh clay will shrink even faster and if it did not pull away from the fired clay while drying, it will surely do so in the kiln.

JohnnyK

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You might just get away with attaching a paper clay addition to biscuit, and re-firing. Whether the join would be entirely trustworthy, even if it survived the firing intact, I wouldn't like to say.

Quote

 

Paperclay is a mixture of clay and paper pulp or vegetable fibre. This mixture has characteristics that make it very different from normal clay. It’s lighter when the cellulose is burnt away; it’s stronger both at leather hard and bone dry state; it breaks with more difficulty and it repairs with ease; fresh clay can be joined to bone dry clay or even to biscuit ware !

Notes on paperclay - La Meridiana Ceramics School - (PDF)

 

 

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11 hours ago, curt said:

Although I do not generally work at low temperatures, I would say unlikely to be strong enough.   The low fire aspect is the problem.  The way particle bonds are formed in low fire is different from high fire.  If you would have said high fire, no problem.  Grog, which is already fired, is a common addition to stoneware. 

 

This is a sculpture / not functional.  but are you saying do bisque at a high fire?

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No I meant do the final firing at a higher temperature.

Bisque firing is at the usual temperature.     If your piece survives the drying process and the bisque firing, and the final firing is high enough, then particles may join together by melting rather than just sintering at the tips (which is what normally happens at earthenware and/or low fire temps)

However if it is just decorative, and your piece survives up to and through the final firing (at whatever temperature that is) then if you handle it very carefully for the rest of eternity you may be OK.  But it will probably be very fragile, and all the more so if your final firing is low temperature.

However, to say much more without knowing specifics like what temperature your clay is meant to fire at, what temperature you are actually firing to, etc makes it hard to conclude anything with more certainty.

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