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skessel1

What happened? Refiring earthenware pottery to repair

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Hi all,

I had a piece of pottery that developed a couple of cracks in the glaze on the handle and when my thumb rubbed it, a few chips came off.  I decided to repaint the undergalze color on where the chip was and did a thin layer of clear overglaze just where I had repainted.  Then THIS happened!!!  Can anyone tell me why?  There are places all along the handle that were perfect after the first glaze firing and after this second one (both at Cone 06), parts that I had not even touched basically burned away back to the bisque.  I am so confused.  Also, was I wrong to reapply the underglaze and overglaze and refire in an attempt to "fix" it?

Thank you in advance.  My heart is broken that this happened and I never want it to happen again!!

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2017-09-26 12.04.56.jpg

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That surface is rejecting the glaze. Is the blue an underglaze? That could be rejecting the glaze. Grind or sand the area that crawled and chipped. Clean it well. get rid of any grit from the sanding.  Try re-applying the underglaze and bisque first before applying the clear. Don't get it too thick.

Marcia

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I’ve had lots of similar problems...   and spent a long time trying to find out why they occurred.  Sometimes it seemed like one particular color underglaze might be problematic.   So, I learned that underglaze ages...  How long has it been since you opened the jar of  blue underglaze?  Underglaze does get old and separates, causing adhesion problems.  If that’s the case with your blue & you’ve had a while, adding some gum Arabic to the underglaze should help.  Because it only happened with the blue and not the other colors, this might be why...  Good luck!

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I've had the same happen.  Clear glaze repelled, when applying underglaze onto bisqued test samples .  I think some underglazes don't like to be applied to bisque, and some on't like to be too thick.

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It's called shivering, and it's not terribly uncommon with low fire white clays. I have never heard a good explanation of why it happens with low fire whites, but maybe @glazenerd will have a good explanation. Once it happens it's tough to get glaze to stick again, but some sanding may do the trick.

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We've had this happen a lot of times at the Paint Your Own ceramics studio I used to work at. We usually would repaint the area and reglaze it and most of the time it was fine. Like Neil said, this shivering is quite common in low-fire.

I don't know why it does this but for us, it usually happened when the pieces were quite dirty to start with (people eating chips while painting their pieces :D). So maybe making sure your piece is really clean before painting and glazing could help?

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