Underglaze

[AWPottery]

I painted an underglaze design on top of a glaze and it doesn't really seem to want to stay on the pot.  The edges on part of the design are starting to curl away from the surface of the pot.  Typically I know underglazes are meant to be painted on in the greenware or bisque state, but where I take classes they have been painting underglaze on top of there glazes in cone 10 reduction.  I was wondering if there was something I could do to make it work?  Do you think the underglaze will stay on the pot even though it looks like it might be curling away from the pot a little?  Thanks.

[Marcia Selsor]

Underglaze means just that. Under the glaze.

Some overglaze decorating colors will work under a glaze, but underglaze does exactly what you describe.

 

Marcia

[Benzine]

Underglazes, just do not look good on too of glaze. As Marcia said, that's not what they are designed for.

 

In my experience, an underglaze on a glaze, gets a "foamy" look to it. I would wager, that is because the underglaze, which isn't designed to melt, begins to do so, because the glaze underneath, is acting as a flux of sorts. With low fire, this is as far as it gets, and it just look generally bad. With high fire, it could perhaps melt enough from the glaze, to look decent. I know quite a few underglazes are rated for low and high fire, so firing them at the upper end of things, combined with the melt glaze underneath might do something interesting...

 

For me, this is all a guess, as I've never tried it at higher temps, and those I've seen at lower temps, were students doing it accidentally.

[potterbeth]

In our studio, we do use underglazes OVER glaze with success. The best results are over a whilte glaze and create a majolica-like effect at cone 6. Many will not completely meld into the glaze if they are applied too thick. Students are encouraged to seek a thinner "watercolor-like" application rather than trying to make solid color blocks. That said, some combinations are simply NOT compatible. This goes for some glaze combinations as well.

[High Bridge Pottery]

Is it curling off before you have fired the pot or after? I couldn't get that part from your post.

 

I have started trying to make myself some good cone9/10 overglaze but only done tests the past week. Right now the recipe is 

 

Red iron oxide 1 tsp

China Clay 1 tsp

Gerstley Borate 1 tsp

 

Somewhere to start.

[AWPottery]

High Bridge- it is curling up around the edges of the pot before it has been fired in the cone 10 reduction kiln.  I'm thinking it will possibly fall off or maybe not stick to the pot when fire; or maybe it will melt onto the pot w/the glaze.... I don't know.

[Babs]

sounds like it truly is an undrglazeandd its composition willnot it allow to be applied to a unfired glaze surface. You could play around with it by adding cmc or even a bit of hte glaze, or gerstley borate. Need to test.

[AnnaM]

AW, do you have access to onglaze powders where you are? I use then to screen print my own decals. They are essentially flux and pigment from what I understand. The ones I use have a firing range of 780-800° C.

If you mix these with a decal medium you would essentially have a type of paint that you could use over your glaze, you could even do some tests and add a bit of whiting to see if that gives them a bit more opacity (whiting doesn't flux at such low temperature)