Long before glazes were discovered, the primitive potter learned to make their objects more appealing by polishing the clay before they baked it. This polishing produced a soft satin sheen. It was accomplished by vigorously rubbing the surface of the item before the clay was completely dry using a smooth stone or soft piece of leather. It was found that by painting the pots with assorted colored clays that had been liquefied, multicolor effects were possible. Polishing specific colors made them stand out more than the ones not polished. American Indian potters still use these same methods to finish much of their wares.
The hobby ceramist can take advantage of polishing the underglazes without having to search out the different clays and making their own. Ordinary greenware can be polished to a fairly high gloss and pieces painted with regular commercial underglaze colors will also accept the polish because many of them are made from a clay base. Items made with the clay polish are porous when they are baked (modern term is fired) and should be used for decorative purposes only. The interior of vases, jars, and other containers can be glazed to make them more functional and easier to clean after use.
The best tool to uses for polishing process is an absolutely smooth stone such as a piece of quartz or agate. Any stone with a glass-like surface can be used. You can often find suitable stones alongside river or creek beds. As an alternative, you can use a soft, lint free cloth such as T-shirt material. There is, or was a product on the market called underglaze conditioner that can be of great help with this technique.
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