What makes blue glaze?

What makes blue glaze?

Cobalt in a fired glaze usually absorbs all wavelengths of visible light except blue and this is why a cobalt blue glaze is blue. However, two or more colorants in a glaze interact so that the wavelengths of light absorbed are different for the combination than for either colorant by itself.

What is a high fire glaze?

High fire glazes are typically fired at cone 9-10. Mid and high fire were historically used to achieve more muted, earthy colors. But glazes have continued to improve and now many different glaze characteristics can be achieved at each of the firing temperatures.

What creates the color in a high fired glaze?

The color develops chemically as the glaze melts during firing. It comes from interaction between the gas, oxygen, and glaze ingredients. The colors in the glaze come from the metal oxides (such as iron oxide or copper oxide) we add to the glaze mixture.

What are the 4 main ingredients in glaze?

A basic understanding of glaze application and firing yields consistent and desirable results, as the key components of different glazes each have their own function.

• 01 of 04. Silica: The Glass-Former.
• 02 of 04. Alumina: The Refractory.
• 03 of 04. Flux: The Melting Agent.
• 04 of 04. Colorant: The Beautifier.

Why did my glaze turn brown?

High-fire, high-iron content glazes fired in reduction will yield glossy dark brown or brownish black. In thin areas, the iron may reoxidize during cooling. Reoxidization will result in those areas turning red or gaining red highlights.

What does copper oxide do in glaze?

Black copper oxide (CuO) is a blackish-grey powder used as a colorant in the preparation of slips and glazes. It acts as a flux and produces fluid glazes. Black copper oxide can also be prepared as a wash and used for brushwork application to bisqueware.

What Cone do you fire glaze?

For example, most commercial glazes recommend bisque firing to Cone 04, and glaze firing to Cone 06 (which is cooler). The reason for this is to make sure all the carbon and other materials in the clay burn out during the bisque firing.

What is the difference between low fire and high fire glazes?

Low fire is usually cone 06-04 (see chart), whereas High Fire (or some call Mid to High Fire) is cone 5-10. The difference between them is the temperature at which the clay matures “fuses” and glazes “melt”.

What does a base do in a glaze?

A base glaze is one having no opacifiers, variegators or colorants. Thus it should be transparent if glossy and translucent if matte. Developing or adapting a base glaze for your ware is a very important first step in developing a manufacturing process that produces good quality.

What does Whiting do in a glaze?

Whiting is the commonly-used name for calcium carbonate (CaCO3), which is the most common source of calcium in glazes. It is a high temperature flux which gives durability and hardness to glazes.

Can you glaze fire twice?

Pottery that has already been fired with a glaze can be re-glazed and fired 2 times. After the 3rd or 4th time, pottery starts to become brittle and weak, but that’s because of the firing and not the glaze itself. There are many situations in which you might need to reglaze your pottery.

What kind of glaze to use for blue celadon?

It is quite simple to create a blue celadon suited to your particular firing style using Tichane’s methods and triaxial blends. From a triaxial blend of potash feldspar, silica, and whiting I arrived at a recipe suitable for Orton cone 11-12 reduction firings: 56 feldspar, 30 silica, 14 whiting plus .6-.8 yellow iron oxide.

What kind of glaze can be fired at cone 10?

These glazes can be fired in oxidation or reduction. This is a very dark brown and fairly static satin glaze at cone 10. These are dark brown to black glazes that usually “break” to a straw colour, mid brown, or iron red where they are thin.

What kind of glaze is used in wood fired kilns?

In the wood fired kiln, the clay body had more influence on the appearance of the glaze. This was my own attempt at a “nuka” style glaze. A28 wood fired to cone 10 in reduction. The real thing is mostly made from rice straw ash, but East Otago New Zealand is not a great rice growing area, so an alternative needed to be found.

What kind of glaze to use on violet ring?

For violet with a dark “break” over rims or throwing rings, add 1 percent cobalt carbonate. An excellent book called “The New Potter’s Companion”, by Tony Birks gives a list of several useful stoneware glazes. One dolomite matt glaze has the mysterious name, “BNO”.