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Eléna

Cone 10 Clay Contamination With Cone 6

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Hi Everyone,

I am new to this forum. I have been making pottery for 14 years with both cone 10 or cone 6.

I just realized I made a mistake : I didn't pay attention when I recycled my clay, and I mixed around 20% of porcelain cone 6 with 80% porcelain cone 10. I threw several pieces with this..."new clay". I have never done that before. Can I fired them at cone 6 without creating any problems in the kiln? Or it would be better to throw my mixture away? Or, can I just fire my greenware (first firing) and forget the second firing (firing with glazes)? Does someone has an idea? Thanks

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Welcome to the forum!

You are not even close to being the first potter to do this ... Or the millionth ... I would guess we all have had a moment when we just guessed at unmarked bags of white clay.

Usually you can just default to the lowest temperature ... Cone 6 ... and fire on that schedule.

No problems with the kiln, but you might have problems with glaze fit, so test the functional wares.

Good luck!

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As Chris says fire to cone 6 and do not worry about it.

If you use two different temp clays its just a matter of time befor a mistake like this ahppens no matter what you do.

I used to keep my lower temp clay out of the studio until it sunck it and ruined a glaze load-then I tossed all lowewr temp clay and do not allow it on the property.

I will add again its just a matter of time-I have seen this disaster so many times at schools I cannot count them.

You are lucky and caught it early.

Mark

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I think that if your new mix is 20% of ^6 and 80% of ^10 clay then the pots we likely be weepy at ^6. I would fire one and test it's absorption before doing them all if you are making functional pots where leaky pots would be an issue.

 

Being porcelain, I think there's a good chance it will still be tight enough at cone 6. Always good to do a test, though.

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did the same thing with some of tom coleman's cone 10 porcelain and elaine coleman's cone 6 porcelain.  made a great vase, i love it, the color inside came out soft blue and the exterior is white.  thought it was the cone 6.  it wasn't and it leaks all over the place.  now it holds tools.  

 

maybe a way to keep them separate is to use black plastic bags for one and white for the other, once you solve the current problem.

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try putting a test piece in cone 10 firing, it might shrink a bit more but it will vitrify. Put a bit of extra kiln wash where you'll place the test in case it wants to fuse to the shelf. Should be usable, just test. If you are firing gas for cone 10 just place it in a cool spot in the kiln.

Wyndham 

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Standard 257 cone 10 grolleg porcelain is listed at 1% absorption at cone 8. Should still be well within acceptable range at cone 6. Highwater Helios is at 1% at cone 7. At cone 6 most cone 10 porcelains should still be around 2% or less. They start at less than 0.5% or less at cone 10, so at cone 6 they are still quite tight. It's not the same as a stoneware which is at 2% at cone 10.

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