Underglazes are used in pottery to create designs and patterns that come up through the glaze covering them. This can give the surface more visual depth and character. Although they are often used under clear glazes, they can also be used under other, generally light-colored, transparent glazes. So, what really are "underglazes"? There are different types, and they can be confusing.
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Commercial underglazes used to be formulated to be basically highly pigmented colored slips: raw pigment, plus clay, plus water. Like all slips, they were made to be applied to the wet or leather-hard clay before it was bisqued.
Today, most underglazes on the market are formulated more like engobes. They are created using fritted material, which reduces shrinkage and allows them to be applied to bisqueware. (In some cases, they can be applied to both greenware and bisqueware.)
Besides liquid underglazes, there are increasing options available for underglaze application. These include underglaze pencils, crayons, chalk, and semi-moist pads which can be used like watercolors.
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Underglaze Product Options
There are many products to use for the underglazing process and a few good ones we can recommend are as follows:
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Slips have been used since prehistoric times as a pottery decoration. Slip is, at its heart, basically nothing more than clay particles suspended in water. Since there are many naturally occurring colors of clay, the earliest slips were able to add several distinctive colors to the pottery they adorned.
Slip can be used in a wide number of techniques, from simple brushed on patterns to the bas-relief embellishments of paste-on-paste.Continue to 5 of 5 below.
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At their simplest, stains are raw ceramic pigments suspended in water. Commercial stains are carefully prepared and blended so that pigments are consistent and reliable in color and how they handle.
If you are using raw oxides or carbonates to make your own stains, be sure to use a respirator and rubber gloves as you work with them. Find out which raw materials are hazardous, and how to handle them safely.