Beginning potters can easily make mistakes when starting to glaze. Because glazes work differently than paints, ceramicists must take time to learn how and when to use certain glazes. With practice and experience, potters will understand how glazes work best on a piece of pottery.
Applying Glaze to Ceramic Bisqueware
All glazes are not made equally. Glazes come in many forms including underglazes, low-fire glazes, high-fire glazes and overglazes. It is important to understand the differences in glazes to use them appropriately.
First, underglaze is a glaze that is used primarily for painting designs onto a piece of pottery. The underglaze is painted on a piece of bisqueware before any other glazes are added. It is important to note that liquid glaze color can differ dramatically from fired glaze color. Because glazes are made from silicates and chemicals, the color can go through drastic changes during firing. Because of this, it is important to read directions and color information on each jar of underglaze.
The underglaze is intended to be used with an overglaze that will create a glossy finish on the pot. Underglazes are usually paired with a clear overglaze so that the colors of the underglaze will be clear and bright. The overglaze can be applied by dipping after the underglaze design has been painted.
Glazes also come in low-fire and high-fire varieties that are fired to a specific cone. A cone in ceramics refers to the temperature at which the kiln is set. The low-fire glaze is intended for use in kilns that fire to a ceramic cone of 06-04, which is around 1800-2000 degrees farenheit. High fire glazes are fired between cones 8 and 9, which is around 2200-2400 degrees farenheit. If pots are glazed with the wrong type of glaze for the temperature of the kiln, the pot can become discolored and damaged.
Glazing Pottery to Fire in a Ceramic Kiln
Glaze acts like glue when heated. It becomes tacky with heat and will stick to any surface it is touching at the time, including kiln shelves. Because of this, it is important to glaze a pot so that the bottom will not permanently attach to the kiln shelf. There are a couple of ways to keep the base safe when firing.
First the bottom of the pot can be waxed before glaze is applied. Paraffin or beeswax can be heated in a shallow electric skillet and the base of the pot can be dipped in the skillet so that the wax coats the bottom. After the base has been waxed, the pot can be dipped in the desired glaze. After the glaze has dried, the bottom of the pot can be wiped with a wet washcloth to remove any residual glaze. The pot can then be fired safely and should not stick to the kiln shelf.
A pot can also be glazed normally when using a tripod. A tripod elevates the pot so that it does not touch the kiln shelf. It is still necessary to use less glaze on the underside of the pottery when using this technique. Before using the tripod, it is wise to wipe off the area on the base of the pot where the three tripod points will touch the pottery. These spots can be wiped clean with a wet washcloth. The pot can then be fired on the tripod without fear of damage.
Practice Glazing Techniques to Create Beautiful Pottery
Finally, it is important for potters to practice and test different glazing techniques to understand how the glazes work during firing. By testing and experimenting with different glazes, the potter can discover successful glazing combinations that result in beautiful ceramic works of art.
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