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Glaze Pooling At Bottom Of Fired Pieces


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#1 Kilini

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Posted 18 June 2011 - 01:25 PM

I just started 6 months ago so I'm a newbie. A couple of my pieces have had glaze pool in bulges at the bottom. I need to know why this happens - is the glaze too thick? Can I sand or file it down? (i've attached a photo)

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#2 bciskepottery

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Posted 18 June 2011 - 08:55 PM

Your glaze application is too thick. Possible reasons: holding it in the glaze too long; bisque is too porous; or glaze in the bucket is too thick and needs to be thinned. If you are in a studio situation, you can do a shorter dip in the glaze bucket and/or wipe the pot down with a wet sponge so it is not as absorbent when dipped in the glaze. If you are working with your own glaze, you could thin the glaze down by adding small increments of water to get a better consistency. You could also bisque to a higher temperature, which would make the pot less absorbent.

When making your pots, think about adding a glaze catch to the foot -- that can help prevent runny glazes from flowing down onto the foot and kiln shelf.

You could grind down the glaze drip; small ones can be done easily, but larger ones look like a glaze drip that was ground down. I use a Dremel with a grinding stone for touch up work. You could throw a couple of new pots in the same amount of time you would spend trying to fix the ones with drips. Not all glaze drips need to be ground; some are quite pleasing aesthetically -- especially oil spot glazes.

#3 Marcia Selsor

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Posted 19 June 2011 - 09:58 AM

I agree with the above. Too thick. I wash my pieces before glazing. Try to get less glaze on the surface. Also may have gotten hotter than the maturing temperature of the glaze. What was it suppose to look like?
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#4 Kilini

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Posted 19 June 2011 - 11:31 AM

I think the glaze was too thick - and probably should have been thinned with water a bit.

I have one vase that has a bit of this happening and it is actually esthetically interesting. But not in the case of this little pitcher. It's too bad because I am happy with the the glaze - other than the bottom!! I may try to grind it, but I hear what you are saying in that it might be faster/better just to do a new pot. It's all a learning process for me right now.

Thanks for your help!

#5 Natas Setiabudhi

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Posted 21 June 2011 - 10:49 AM

Another thing, may be you used oxides that make the glaze flow to much (running glaze), usually if the recipe contains much zink oxide and low alumina. But it can be interested thing (natural melted), your glaze dip just end at the middle, so if glaze melting and flow not drop to the shelf.
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#6 Guest_HerbNorris_*

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Posted 21 June 2011 - 02:53 PM

I just unloaded a kiln last week where the glaze ran just like that on about six mugs, the glaze was much too thick. I've been doing this for five years, so it can happen even after you have some experience , I guess.
I've tried grinding these drips with a Dremel, and it's rarely worth the time, it never looks quite right. Better to start over, as others have suggested, I think.




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