Pottery and Ceramics Glaze Decorating with Oxides

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More than likely, you have never heard of oxides and you probably never will unless you work with pottery or ceramics.
Even working with pottery and ceramics, in this day and age, you won't be introduced to the word, because the stains and glazes that you will be working with are ready made.
Oh, I take that back, you might see the word if you read the labels on the glazes that you are using!!!!
I thought I might tell you a bit about oxides in case you want to do some experimenting.
Oxide is described in the dictionary as any compound of oxygen with another element.

How does oxide compare to stain?
Oxide is a raw material.
A stain is a blend of raw materials, including oxides to achieve a consistent color.
Glazes and slips made with stain will generally be more uniform, but those made with oxide will be more splotchy, specked, which some people see as beautiful!
There are four main color additives used.
Some are called oxides and some are called carbonates, such as cobalt oxide and cobalt carbonate.
The oxides are usually stronger in color and more speckled.
The carbonates have finer ingredients.

Oxides can be mixed with water and added to clay and knead in, but this would be quite expensive for deep coloring of large pieces.
They can be added to slip or glazes.
Mix with water and mix often as it settles out fast, brush on bisque and fire.
This is a way to get natural looking surfaces.

Iron Oxide

This comes in many types and can provide a wide variety of colors under different firing conditions.
Types of iron oxide are red iron oxide, black iron oxide and yellow ochre.
At earthenware temperatures, up to 4% oxide will produce amber and honey glazes.
At stoneware temperatures it can be applied directly to stain the clay surface.
It is often used in this way to highlight textured surfaces.
It can also be added to the glaze.

Cobalt Carbonate - Cobalt Oxide

This is the most powerful color and produces various shades of blue.
It can be harsh if used by itself, so is sften mixed with iron, manganese, magnesium or copper to create more subtle colors.
Like iron oxide, it can be added to the glaze or can be applied to the clay surface and fired to stoneware temperatures.
By itself it will tend to create a dark slate metallic finish.
It can be mixed with manganese and iron to product rich black slips.

Copper Carbonate - Copper Oxide

Copper should not be used in soluble glazes for food and drink containers, they are not food safe and will leach into tea for example, making your tea have a coppery taste.
It is not very effective used on it’s own.
Better to add to or cover with glaze.
In an electric kiln it will create a variety of green shades.
In alkaline glazes it will create turquoises.
It can achieve red colors in a reduction kiln.

Manganese Dioxide - Manganese Carbonate

In glazes these create colors such as mauve, purple and brown depending on the other ingredients.
By itself it produces an attractive brown with tiny metallic specks at stoneware temperatures.
The dioxide is more speckled than carbonate.
It is often mixed with other oxides such as cobalt to create purples and iron to produce rich browns.

There are others like chromium and nickel, but they are not as predictable throughout all of temperature ranges and should be handled carefully as they are toxic.

If you make your own glazes, you already have seen many oxides used in glaze recipes.
It is probably best, when first starting out, to stick with recipes for colored glazes.

How to experiment with oxides.

Brush oxides on greenware, bisque and glaze.

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Make some slip and add some oxides to create your colors.
Mix well to get more uniform colors.
To get more random, blotchy colors, don’t mix well.

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Brush oxide wash over an unfired glaze, then fire.
Be very careful when handling because you can smudge the oxide.

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Brush oxides on, then apply glaze.
Best to dip or spray to avoid brushing the oxide off, and if dipping it is best to put some glaze aside so oxide doesn’t contaminate your whole batch of glaze.
Generally the stronger the oxide wash, the more it will bleed through the glaze.
Where specified by the manufacturer this is explained on the specific glaze label.

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Mix ball clay with your oxide and water.
It give you a better consistency and tones down the color.

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Brush a couple different oxides on and overlap in areas.

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Sgraffito
Brush on oxide.
When dry, scratch with a sharp tool through the oxide to show the clay underneath.
Cover with transparent or translucent glaze.
You can do the same thing with oxide over unfired glaze too.

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Spatter wax on the surface and paint the oxide wash over that.
Once the piece is fired, the wax will burn off and give you an neat effect.

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Use other masking techniques, such as torn, wet newspaper and paint an oxide wash over it.
When this is fired, the paper will burn away and it will give you a different effect.

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Sprinkle a variety of different oxides on a newspaper.
Lay leather hard objects onto the newspaper and oxide mixture.
You can also use a piece of styrofoam or a sponge to pick up the oxide and blot it on your piece.
Keep the pattern as it is blotted or you can smear it around.
If you’re once firing you can add glazes.
Otherwise fire to bisque and apply glazes, the oxides will still interact with the glazes when fired together.

Oxides are strong colorants, so a little bit goes a long way.
In a solution you will probably only want about 2 to 8% or you will end up with black.

Always use a respirator or mask when handling the dry oxides.

Using oxides like this will provide unpredictable, but sometimes beautiful results.

Test!
Take Notes!