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Nancy S.

Glaze Flaking Off

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I looked around and didn't find any other posts on this, so hopefully it's not a stupid question.

 

I have a bowl that I glazed today with two others. They were all bisqued to 05, all made of Standard 630. I sponged them all off and glazed them in Coyote black, then one got a few layers of Plum Shino, while the other two got Leopard Shino. One of the latter two...well, it looks like the Shino flaked but the black is still on. What caused this? Too much water when cleaning them off? Or something else? Also, what's my best option to fix this one? Scrape off the flaky bits and reapply? Or do I have to wash it all off and start over?

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Did you put the second and third coats on fairly soon after the base coat? Sometimes get flaking if the base coat is too dry. Another cause is from having a lot of kaolin in the glaze but since these are commercial glazes there is no way of knowing this.

 

I would wash the glaze off, dry the pot and start over. Try the combo on a test tile first so if it flakes off again you are not wasting as much glaze.

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It was my understanding that most shino glazes contain a higher percentage of clay than other glazes and should be applied to the pot first. I think that because of this, shinos do not generally work well over other glazes and will tend to curl up and flake off, as you experienced.

I am not sure if this holds true for commercial glazes however and hope someone else with more experience will weigh in here. 

 

 

Susan

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This is a commercial glaze called a shino; meaning, it is a glaze that is manipulated and intended to look like a shino after it is fired.  I doubt the glaze is actually formulated like a shino glaze one would mix themselves from raw materials. 

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Chilly, this wasn't even fired yet, so the other post doesn't quite apply.

 

These 'shinos' actually do quite well over other colors, especially the black...usually. Upon closer inspection it looks like the black got pulled up, too. But the really odd thing is that this only happened on ONE pot. The other, done the same way on the same day, is fine. I'll scrub it off and try again. How long should it dry after cleaning?

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Another appreoch is to lip dip as soon as you dip the 1st glaze so both layers are wet. This works well with a few of my glazes-if the first one is dry the second peels-so I do them both wet and as claose together as I can time wise.

Mark

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Chilly, this wasn't even fired yet, so the other post doesn't quite apply.

 

 

Nancy - that thread was about bisque'd items that were glazed, then flaked before they were fired.

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Chilly - Ack! Sorry, I misread the post (same as someone else)...I think because I saw "in the kiln" and jumped to the wrong conclusion.

 

So how'd that "brushing medium" work for your flaking problem? And is it just sodium silicate? (Because I do have some of that handy!)

 

 

Mark - I don't have enough of the glaze to dip. It's all being brushed on.

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So how'd that "brushing medium" work for your flaking problem? And is it just sodium silicate? (Because I do have some of that handy!)

 

 

 

It worked.  I used around 12% and it did crack a tiny bit, but didn't flake off.  I had to us a toothbrush to remove it.  I've no idea what it is, it's different to the sodium dispex that I have.  Been meaning to reply to them and ask......  I'll let you know what they say.

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Have you layered these glazes successfully before? It's rare, but in my experience some commercial glazes just don't "play nice" with each other.

 

It's also possible that the total number of layers applied resulted in too much total glaze thickness. If you're brushing, most commercial glazes seem to prefer no more than three total coats before excess thickness can cause problems (for example, 2 coats black plus 1 coat other glaze for 3 coats total). Of course, the liquidity of your glaze will impact that...I'm basing the 3 coat norm on the glaze having the consistency of heavy cream.

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If my brush on glaze is all gunked up and hard in the container, can I add a little water and mix it up well to a consistency that I can then brush on? 

thanks, Hetty

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Hi Hetty!

My guess would be yes; likely it's the water that has evaporated. Once you've restored the consistency, try brushing a bit of it on a comparable potshard, or on a piece you don't mind washing off, waiting on drying, an' starting over should it rope up on you. I'm not using commercial glazes, but I do re-wet underglaze that's dried up without issue...

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On 4/1/2019 at 3:07 AM, Hetty said:

If my brush on glaze is all gunked up and hard in the container, can I add a little water and mix it up well to a consistency that I can then brush on? 

thanks, Hetty

Maybe. Add water and use a stick blender to get it smooth. It may or may not brush well, though. If it doesn't, you'll need to add a brushing solution to it.

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16 hours ago, neilestrick said:

Maybe. Add water and use a stick blender to get it smooth. It may or may not brush well, though. If it doesn't, you'll need to add a brushing solution to it.

Yeah, water isn't always the answer.  I have a particular commercial glaze, that thickens in the bottle, sometimes before the seal is even broken.   I've tried adding water, a brushing additive, and even tried to deflocculate it.  I haven't found the specific solution yet.  I just need to contact the company, and see what they say...

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