Ceramic stains can refer to ceramic colorant oxides suspended in water or to prepared coloring oxides (commercial stains). Colorants generally are sold in powder form and commercial stains may be either sold in powder or liquid form. Stains can be used by themselves as an underglaze color, in slips, in clay bodies, in glazes, painted on glazes, and in overglazes. One of the biggest draws for using stains is to achieve very consistent color, as sometimes using a coloring oxide can have a less predictable outcome.
Many commercially available stains are fritted for safety, then reground. A frit is a ceramic material that has been 'fused, melted or sintered together' in a kiln. According to Ceramic Arts Daily some of the earliest recordings of this kind of method date right back to 2600 BCE. For example the beautiful Egyptian Blue. The reason frits are added to stains or coloring oxides is that they help the melting process. Some, especially oranges, reds, and yellows, have their volatile coloring oxides encapsulated in a coat of zirconium silicate, (zirconium silicate is a colorless chemical compound). This manufacturing technique has significantly increased the firing range for many colorants.
Depending upon the strength of the colorant, full color can be achieved in a transparent glaze anywhere from 1 to 5 percent, in an opaque glaze from 5 to 10 percent, and in slips and clay bodies from 10 to 15 percent. Stains, like all colorants, can result in very different colors depending on the firing range and, especially, the firing atmosphere. Also, glaze components can have a significant impact. When using commercial stains, note and follow all directions for use, including what types of glazes are appropriate for that particular stain. It is important to note that the more stain that you use on your piece, the darker the color will be.
Because ceramic stains consist of metallic oxides, always consider safety. A stain is a mix of metal and ceramic oxide that has been ground into a powder. Stains and oxides can be very toxic, so you must make sure not to have food or consumable liquids when you are working with them. Even if you are working with fritted stains you should make sure you use a respirator with dry materials and control all dust created.
Note: There are also organic dyes which are sometimes used to color raw stains. These dyes help potters have a better idea of what a fired ceramic stain may look like (but is by no means exact). Because they are used only to help identify raw stains, they are sometimes referred to as distinguishing stains. These organic compounds burn out during firing and do not affect the final product.
Also Known As
Prepared stains, prepared oxides, modified oxides, inorganic colorants, coloring oxides
How to Use Stains
When introducing a ceramic stain into a glaze recipe, it is best to mix powdered stain with hot water, sieve through a 200 mesh screen, then add to the wet raw glaze batch. This aides dispersion and reduces speckling.
Another great benefit of using a ceramic stain is that they will look very similar once fired, so it is easy when glazing to apply the exact color that you want.
Stains are great if you have highly decorative work to fire and they can be fired at a range of different temperatures. There are several factors you should consider when picking your stain including glaze chemistry and working out how the glaze will react with the clay body, exact color (which is easy to see with a ceramic stain), and also the temperature in which you will be firing your stain at. Your stain can also have varying densities, depending on how many layers of color you wish to apply.
With ceramic stains your creativity can run wild as the spectrum of colors that you can mix and produce is vast. If you want to create a painted effect on your ceramics, then this is one of the best ways to achieve it as you have complete control over the range and the density of your color.