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About Polishing Underglazes: Article or Project

Variety of underglazes, clear glaze, suitable greenware. Also, cleaning tools, sponge, bowl of water, smooth rock or small spoon, soft cloth.

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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.

Step 1 - Carefully clean the dry greenware. Then sponge the entire outer surface with a wet sponge.

Step 2 - Dilute your background underglaze color with an equal amount of water. Use a 1 inch soft glaze brush to apply one coat of the diluted color to the greenware. Then use the same brush to apply 3 smooth coats of the full-strength color. Always apply regular underglaze colors to freshly cleaned greenware or dampen the surface of the ware which has previously been cleaned. This makes for a better application of your color.

Step 3 - Allow the piece to stand until the final coat of underglaze color has lost the wet look. This should take no more than 2 or 3 minutes. You only want it dry to touch. Using a facial tissue or a piece of soft cloth, begin to rub a small area of the surface of the piece; continue rubbing until the color appears to darken and take on a soft sheen. In this manner, polish the entire surface of the piece. Remember you are working with greenware, so handle carefully. Unless the greenware is extremely large, enough moisture should remain from the cleaning and application of color to complete the initial polishing before the surface becomes too dry. Should the piece dry out before you are finished, use a sponge and lightly dampen the remaining area, again wait until it loses its shine. You could also lightly spray a mist of water. If you are using the underglaze conditioner, just apply more to the area as needed.

Step 4 - Using a polishing stone, or the bowl of a spoon, vigorously rub the surface of the piece to burnish the underglaze color until it is shiny. Dampen the piece as your work progresses so that the burnishing is always being done on a damp area.

Don't hurry with this step. The degree of sheen attained will be in direct contrast to the time spent in polishing. For an extremely high sheen, lightly rub the surface of the piece with a cloth saturated with lard, vegetable shortening or cooking oil several times during the polishing process. Indian potters of the Southwest lightly rub their pieces with lard, not only to attain a high sheen, but to prevent chipping the surface of the ware with the friction caused by the polishing.

Step 5 - With a blunt, soft lead pencil, lightly sketch a design on your polished item, or you may trace a pattern using a piece of graphite paper.

Step 6 - Place some assorted colors of your choice of underglazes in separate areas of your palette or a glaze tile for easy access. Do not thin the colors.

Fully load a wet sable brush of adequate size and paint your pattern. If you are doing something with flowers, you may want to use translucent colors. If you want something more defined, use 2 or 3 coats of whatever underglaze color you desire. *

Step 7 - Fire the piece with any lids in place to cone 05.

Step 8 - Roll the interior of any container with a diluted glaze approximately 4 parts glaze to one part of water. Make sure any spills on the outside are wiped clean from the exterior. (There are exceptions for diluting glazes, such as bold opaques may need to remain full-strength). Using a small soft bristle brush, paint two coats of glaze on any part of your design that you want to have contrast. I highly recommend you leave some of the design unglazed for greater accent.

Step 9 - Fire the pieces separated, to cone 06

* watch for patterns and project designs that could be utilized for this project.


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