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Base Of Pots 'chipped Edge' After Glaze Firing - Why?

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#1 oly


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Posted 18 August 2014 - 04:41 AM

The attached picture shows the chipping that has occurred to the bottom edge of pots as they have come out of glaze firing (c1240 degrees centigrade – cone 6-7). The edge was perfectly smooth when it went in the kiln.


Larger pots affected worse than small ones.


Clay has some grog in it.


There is a layer of bat wash on the kiln shelves.


Any help gratefully received!

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#2 Biglou13


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Posted 18 August 2014 - 05:14 AM

Could be pluckng?
What kind of clay?
That's not a problem, a few passes with diamond pad and you're back to new.
Try putting some silica on shelf before next firing. See if it does it again?
Did all pots have this!
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#3 TJR


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Posted 18 August 2014 - 08:56 AM

The term is "plucking". It happens with porcelain quite frequently. When waxing the feet of my porcelain bowls, I put a bit of alumina hydrate in the wax. Problem solved?


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#4 sankayknow



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Posted 18 August 2014 - 02:29 PM

I had this happen recently.  My chips were much larger and could not be sanded out too look decent enough for selling.  I have never had it happen before.  I lost about 4 mugs to this.  The studio manager thought it might have been due to the kiln wash being too thin on the shelf, or at least needing to be redone.

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#5 neilestrick


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Posted 19 August 2014 - 08:23 AM

You need a fresh coat of kiln wash on the shelves.

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#6 Brian Reed

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Posted 19 August 2014 - 03:37 PM


I do not use Kiln wash I simply brush a light dry coat of Alumina Oxide on my shelves and call it good.  No more chips on my large porcelain bowls.  I believe this happens during cooling where the pot cools at a different rate than the shelves while the pot has stuck slightly to the shelf. 

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Brian Reed

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