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Cavy Fire Studios

Wedging Lesson

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So, a long while back, my hands were in a good mood, so I threw some pieces on the wheel. I had forgotten to wedge one of the balls of clay, and like a VERY BAD guinea, I said, "Ehh, I'll just throw it anyway."

 

Well, I trimmed the mug, and it was dry for WEEKS before I decided to decorate it. I made a cute stylized kitsune fox on it, and intended it for my hunny's Xmas present.

 

It. Blistered. Like. Chicken pox.

 

That mug was the ONLY PIECE that came out like that (of course). I was like, wtf??? So, I sanded down the blisters, filled them with more glaze, and refired.

 

Blistered AGAIN...and my underglaze started to bleed.

 

HNNNGGGGHHHHH!!!

 

Lesson learned!! Just because a clay ball is squishy, it doesn't mean it's ready to throw!

 

Do any of you oldschoolers think that might've been the problem?

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I have no explanation for glaze blisters. I have had it happen to me once on one piece. It was made of the same clay, glazed with the same glaze at the same time as a piece of about the same height that was next to it in the firing without issues. They didn't all go away after being refired twice.

 

I don't think it has anything to do with wedging the clay though. I have thrown many pieces of reclaimed clay that weren't wedged except for the quick coning on the wheel.

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Wedging is very hard on my hands so for small pieces, which is mostly what I make, I don't wedge clay straight out of the bag.  I just cone it on the wheel. Naturally, I do wedge reclaim.  Intuitively, it doesn't seem like that ought to be the problem, but then I'm not one of those been around the moon twice potters. (Old timers)

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Too sad to think of all the time you spent on this piece!

I find it hard to imagine any lack of wedging would cause the clay to blister. It seems more likely that the surface became contaminated after it was thrown - potato chip fingers?, hairspray overspray?, guinea pig snuggles?

Were there blisters on unglazed areas?

Is there any kind of pattern to the problem areas (spaced like fingerprints?, one side only?), or is it all over? Inside and out?

Curious . . .

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Just my blue glazed parts, but the clear was fine as wine! :( Also, I'm suuuuuper paranoid about having clean hands when working with clay. I even strip the oils off my skin with cheap dish soap before I glaze! :D I put so much time into the surface decoration that I rarely take risks or shortcuts. I think maybe it was just a freak accident, lol...

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Just a side note -I never wedge my porcelain for work under 6 #s-never been an issues . I used to wedge  all clay over 3# but after wrist surgery I gave kit up except for larger work.

No issues in glazing

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 I think maybe it was just a freak accident, lol...

Wheeeeeeek !!! Sorry this happened... That is so very odd... I would think pinholes before bigger blisters with a some blue glazes... Usually the more Maganese you have the more likely it is to blister... I had a Black clay that was loaded with Mag. wow that body gave me fits until i let it set long enough in the bisque to burn it off.. I think Joe told me about that? not sure... Pinholes can be fixed pretty easy, just down fire it to let it cool slower... I have had blue glazes and some glazes i applied to thick pinhole ... we call em moon art LOL...

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We ALWAYs get the pox blisters when we use our matte alabaster glaze in Standard 710 or Laguna B3, both are black of bear black bodies. The same glaze never blisters on our white stoneware or porcelain. We have never investigated the reasons, only avoided the combo. I suspect that these blisters are more due to a specific out gasing from something unique to these clays (manganese?)

 

We get smaller blisters that pop and form craters in the glaze surface. These tend to be less numerous, flatter, and smaller. These can show up in just about any glaze / cljay combo under the right conditions. We can eliminate these by slowing the downfire, in our case to 100 degrees to 1900. We've been able to elimate 100% of this type of blister.

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