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Yawnoc

Glaze over underglaze

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Very new to pottery and first time I’ve created and used a underglaze. Made at instructed stain,general medium and a little water to cream consistency. Looked great. Glazed over with brush on clear gloss. When it came out the kiln the glaze peeled off. Any help please

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Hi Yawnoc and welcome to the forum. Could you give a little more information about the underglaze recipe you used? Also, a picture of the problem glaze/underglaze would help too. Peeling glaze could be shivering or glaze crawling back but it's hard to say without more info.

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5 hours ago, Yawnoc said:

When it came out the

Hi---it might also be helpful to describe the cone/temp fired to, and whether you control the kiln or is it a group kiln that someone else runs?

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Did it peel off everywhere, or just in spots?  Underglazes can be tricky to make, which is why many potters just use commercially made versions. 

I've had a few issues with something similar, where an underglaze flakes off, in spots, after being fired, sometimes after the glaze firing, sometimes after the bisque.  In some cases it was right after the firing, in others, it was months to years later. 

In most instances, I chalked it up to either a bad batch of that underglaze, or just applying it to a surface that had some type of contaminate that prevented it from adhering well.

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Hi

I mixed the underglaze 50g stain 37g general medium and added water till it was cream texture. Was only test so didnt want to mix loads.

I fired it to cone 04 (1050 c)  as it was earthenware and that's recommended by glaze supplier.

In the kiln was some items using the same glaze with the same  stain added to the glaze, they came out great.

All the glaze peeled off totally. It was like the underglaze didnt react at all. I'm going to check the temperature for the stain.

 

 

Edited by Yawnoc

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If the glaze was otherwise well behaved on other pots in the same firing, that makes me think there's something up with the underglaze. Some stains can be fairly refractory, so do you have the number of the one you used? Also, What general medium were you using? Is it a commercial product, or something you've made yourself? We really would love to see pictures of how the glaze is flaking off, as that would give us a world of information to help you diagnose. If you have a smartphone, photos can be very easily uploaded at the correct size to the forum through that.

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Aha Y if you post here you gotta give more info. 

I'm curious about general medium too. 

How thick was the underglaze you applied.  How did you apply and how many layers did you use. 

Did the rest of your class use the same underglaze or did you make yours separately.  

Though my knowledge of earthenware is very limited I must admit. 

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Think I've sorted it. I'd need exactly the same process on green ware and it came out great. I did read that some underglazes dont work on high bisque as the cant bond. I'm guessing that was my problem.

 

Thanks all 

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