Oxides over white glaze?

[Earthandwater]

Hello,

I have a question about glazes and oxides. Usually, I do my oxide brushwork on greenware, and then coat the bique with transparent glaze.

I often use darker clay, and then I usually apply some white slip or underglaze, before brushing on the oxides. But then I found a picture of a small pot from the potter Robyn Cove. I do similar style brushwork, and have always wanted a consistent white background, but on a darker clay. This potter does exactly that, but I have no idea how. It does not look like underglaze at all: it looks like everything was coated with a white glaze, and then brushed over with cobolt oxide. But at the same time, no bleed, and the oxide and the glaze looks very "melted together". I would love any tips on how I can archieve this!

I am attaching an example (the bottom left).

[Magnolia Mud Research]

1 hour ago, Earthandwater said:

it looks like everything was coated with a white glaze, and then brushed over with cobolt oxide. But at the same time, no bleed, and the oxide and the glaze looks very "melted together". I would love any tips on how I can archieve this!

I have no idea how the potter for the images got the surfaces you are referring, however:

I fire to cone 10 in reduction.  Occasionally I use a low-fire white  commercial  clay body (Longhorn White) as a glaze for my stoneware.   I  make a  smooth slip of the low-fire clay body and apply the slip at the construction stage;   I usually apply at or just prior to the leather hard stage.  Bisque the item and then apply any decorative stain ( for example: cobalt carbonate brushwork) and fire to cone 10.  This process was developed after testing to understand the resulting consequences of the low-fire slip at cone 10 reduction.   

There are white engobes that would do the same as the slip I used.   My guess is that the potter used a a white engobe at the leather hard or later step.  

LT
 

[oldlady]

yes, you can use a wash over a white glaze.   try it and you will see how it sinks into the glaze as it is fired, very much like the photo you like.    for the cobalt, try the carbonate, not the oxide to avoid the tiny specks of very dark cobalt that can happen with oxide.

[liambesaw]

Get a nice stiff tin white.  Oxides won't run (as much) in a stiff glaze

[Pres]

Van Gilder has a series of wash formulas you could use over a white glaze. You can also use commercial stains or underglazes over the white.   Myself, I have a series of glazes I use over a base white, brush work will hold up pretty well. Fired at Cone 6

 

best,

Pres

[Babs]

Can do that with a majolica glaze . 

Research Majolica glaze and Linda Arbuckle.

Majolica glazes allow decoration as in image.

[Earthandwater]

Thanks a lot, all of you!

I will try with a white engobe, and also get myself a nice stiff white glaze. And will def research wash formulas and Majolica.

I really had no idea that oxides could be used over glazes, as the glaze melts - but why not try, right? Very exited about this.

[Earthandwater]

Just one more thing: I I apply the cobalt on the outside, is it then food safe? If it melts into the glaze, I suppose so..

[Babs]

Italians have used the majolica technique for centuries.

Lind Arbuckle shares recipes and techniques freely.

Don't need a white engobe.

Traditionally used over red clay.

Some folk mix a little frit with the oxides and mix the oxides to "dilute" the vividness of the cobalt.

A second, cobalt cut with a bit of iron for a softer colour, then sgraffito to white glaze.

 

 

[Earthandwater]

Thank you so much! Will investigate. It looks lovely!

 

[Babs]

Fettle or smooth over any drips in glaze prior to decorating with oxides.

Some folk find the unfired glaze fluffy and do things to harden the glaze surface.

Think of laying the oxide on as opposed to painting with a bit of pressure if that makes any sense. Cobalt strong fingerprints show. 

Good luck.

Bowl fired to C 6

 

[Rae Reich]

On 4/22/2020 at 11:12 PM, Earthandwater said:

Thanks a lot, all of you!

I will try with a white engobe, and also get myself a nice stiff white glaze. And will def research wash formulas and Majolica.

I really had no idea that oxides could be used over glazes, as the glaze melts - but why not try, right? Very exited about this.

Mix some cobalt or cobalt carbonate into a bit of your white base glaze and use that (maybe thinned for brushability) for decoration on top of the white base glaze. Experiment with different proportions to get the color you like. A base glaze with tin in it produces those nice little white dots breaking through the blue. 

Fired cobalt glazes are food safe when fired to maturity.