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Porcelain and white earthenware mixed up in kiln - which glaze to use?


LouiseB

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Hello, I’m new to ceramics and have been working with some mid-fire porcelain clay as well as white earthenware clay. I made several hundred small jewellery pieces from both clays and had them bisque fired at a local kiln service. Unfortunately they combined all my work together and now I don’t know which is porcelain and which is white earthenware, soI don’t know which clear glaze to use on which piece. 

Might anyone be able to give me some advice about what I could do? Are these pieces salvagable  or bound for the bin? 

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@LouiseB,this is a long shot but I noticed you used the word "bin" so I'm guessing you might not be in North America. In the UK for example there are some earthenwares that go to cone 6. What info do you have for the earthenware you are using? Might be lucky and have one that goes higher than lowfire temperatures.

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Thank you so much for your replies. 

I’m in Australia. 

I didn’t really phrase my question very well.  I’m very new to this. 

I have some pieces made from white earthenware clay and some made from mid-fire porcelain clay. I had them all bisque fired. When I picked them up the eatherware and the porcelain items were all mixed together. I now want to put some under glaze and clear gloss on them and fire them again, but I’m not sure which clear gloss glaze to use. I have purchased one tub of gloss for earthenware and another tub to use on porcelain.  Which one should I use?  And how should I fire them? Thank you soooo much! 

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I think if you look very carefully in good light you may be able to see a difference. The porcelain won't necessarily be smoother, but it may be whiter. The problem is that if you're wrong, the earthenware will melt in the porcelain firing. The only safe way to go is to fire everything at earthenware temps. You may have problems with glaze fit, though, if you use low fire glaze on porcelain.

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On 9/23/2019 at 11:30 PM, neilestrick said:

I think if you look very carefully in good light you may be able to see a difference. The porcelain won't necessarily be smoother, but it may be whiter.

If you can sort them into two sections, you can high-fire one from each section by putting them on a cookie (saucer shaped).  Document shape/size/section.

If you can't sort them, low fire them all.

 

Next time, get them fired separately, or carefully document the shape/size/clay type.

 

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