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shonnie

What’s causing this crawling?

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  I am perplexed why I get this crawling in about 1 in 10 mugs. The mugs are poured in an old hand built mold, from large batches of slip.  At leatherhard cleaned up and sanded when dry. I rinse them all well with a clean sponge after bisquing and allow to dry 24 hours before glazing. The glaze is a large batch I’ve been using for a year. I’ve never seen this on anything but these mugs. 

40182C0F-DF37-4EAA-8714-0AC6FFD5C5AF.jpeg

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Looks like you're copying and pasting "thumbnails", rather than the actual images.  I see a "Photofy" watermark at the bottom corner.  I'm not familiar with that app/site, so can't offer much help in getting the full-size pictures... maybe there's a "share" button that will generate a link - or, maybe you can upload directly from your computer (or device you took the pic's with)

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If you have a glaze with a high amount of uncalcined clay it is going to shrink a lot during drying. Hard to tell by the pictures but are the mugs thin walled? If so when you combine that with a glaze that contains a lot of clay you have a double risk of crawling. (If there are any cracks in the raw glaze before firing then it's pretty certain to crawl when fired.) Are your pots really dry after 24 hours? If they're still damp this is also going to compound the problem of the glaze not bonding with the pot because of being oversaturated. Other things can cause crawling also, dirty bisque from greasy hand lotion or dust or just putting the glaze on too thickly.

On 7/14/2018 at 4:11 PM, shonnie said:

sanded when dry

Can you damp sponge them instead? Not a good idea to do sanding unless you have super good ventilation, or working outside, and wearing a respirator. 

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I downloaded the pictures using my iPhone as I don’t have a computer so they might not work for some of you. But I think Min hit the problem. I’ve noticed it’s more likely with the thinner walled pieces. And only with this tenmoku glaze.  Thanks Min

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