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Glaze comes out matt

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I know this has probably been addressed here before but I can't find the explanation. Two glazes that I use a lot come out of the kiln occasionally with some matt areas. This usually happens when the glaze pools in the bottom of a bowl. Can a glossy glaze become matt with overfiring or underfiring; or is there just too much glaze in this one spot?

Thanks.

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Underfiring can definitely cause matteness. Overfiring can do it too. Glaze puddles will often be more matte as well. Cooling rates can also do it. You'll need to start narrowing down all the possibilities to figure out which one is the culprit in your case.

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Ceramics are mysterious. You couldn't predict the result exactly, even you use same technique and recipes. You must hope to the fire god for succeed the pieces, just kidding guys..

Actually, your experiences is rather odd to me. Usually a matte glaze become a glossy one not opposite. If happen may be it's special condition. May be I need more input for this phenomena.:rolleyes:

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post-2374-132708067908_thumb.jpgpost-2374-132708066417_thumb.jpg

 

Thanks for your replies. I just started firing on my own about a year ago and have much to learn. I like the effect with the ice blue but sometimes Ancient Jasper comes out rather dull and I think this is because it has to be applied so thick.

You can see the crystal formation on the ice blue pieces which I love but not so in love with the jasper surface.post-2374-132708064836_thumb.jpg

post-2374-132708064836_thumb.jpg

post-2374-132708066417_thumb.jpg

post-2374-132708067908_thumb.jpg

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I know this has probably been addressed here before but I can't find the explanation. Two glazes that I use a lot come out of the kiln occasionally with some matt areas. This usually happens when the glaze pools in the bottom of a bowl. Can a glossy glaze become matt with overfiring or underfiring; or is there just too much glaze in this one spot?

Thanks.

 

 

Most matts can go glossy with more heat-also the thickness of application can matter-matts tend to be thicker-and this is why when yours pools in bottom it matts up

you also can get a matt with less heat from a glossy glaze say put in cold flue area

My answer with what you have said is its to thick in this one spot

 

Semi matts are one of my most favorite glazes and have a buttery feel not dry or shiny-they are hard to get consent results with-I have one thats green in cone 10

Mark

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The inside of the bowl appears to be showing crystals. Crystals can form when a glaze cannot keep a dissolved ingredient dissolved. It could be that the thicker area in the bottom of the bowl allows for the glaze ingredients to settle into layers. The top layer might be over full of some ingredient/s that are in a concentration too high for the glaze to keep them in solution.

Try putting a witness cone next to this glaze in the next firing to eliminate any guesswork about the temperature.

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Ben,

This glaze does need to be stirred between every coat(I brush on glazes), so you are probably right. I do put cones in for firing but have not noticed if they were near one of these pieces. Cones show that the kiln reached a full cone 6 and cone 7 is slightly bent. Ice blue is a cone 6 glaze. I love the crystals and would like to keep them so maybe I'll try a lighter coat on the bottom of the bowl to try and avoid the small matt pool.

Thanks

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