Glaze is a hard glassy coating on the surface of ceramic material. Most high- and low-fire glazes help to strengthen the material, while adding a smooth and impermeable surface, and adding decoration through color and surface treatment. Application of glaze is ideal for pottery intended to be used for food, due to its practical and durable qualities. There are, however, some firing processes and glazing techniques, such as raku and pit firing, where the glaze does not create a strengthening or impermeable layer. There are a variety of glaze application techniques which enhance the look of any ceramic item.
Basic dip glaze
The most common and basic glazing method is simply dipping the ceramic item in a large bucket of glaze. This method is widely used for functional pottery due to its ability to get a uniform coat of glaze on the surface of a pot. When glazing pots, apply wax resist to the foot, or base, of the pot and any areas you do not want glazed. Add a cup or two of glaze to the interior of the pot, and rotate the pot in your hands to coat the inside of the pot. Pour any extra glaze into the bucket. Once the interior is coated, hold the pot upside down and dip it straight into the bucket. Be aware of how your fingers or hands are holding the pot. Finger marks will mar the freshly glazed surface if the pot is not handled on an unglazed surface.
Wax resist can be used for practical and decorative purposes. Often times, a decoration is painted on the exterior of the pot using wax resist. Any wax resist on the pot will not allow glaze to adhere. Be careful using the wax. Once the wax has dried, glaze is applied on the pot using the basic dip glazing method listed above. This technique is also used with two colors of glaze. The pot is coated with a base glaze, and then wax resist is applied over that layer of glaze. The pot is then dipped into a contrasting color of glaze. The areas with wax resist will show the base color of glaze.
A pot can have two colors of glaze, similar to the basic glaze dipping method. Coat one-half of the pot with glaze. Once the glaze has dried, dip the other side of the pot in another glaze color. This can be done using multiple colors, but be careful not to add too much glaze or it will run and ruin the kiln shelves.
Underglaze is a colorant than can be used to paint decoration on a pot. Paint a desired motif onto the pot using a paintbrush and underglazes,. Once this is complete, the underglaze is dried thoroughly and then coated with a clear or translucent overglaze and fired in a kiln. This method helps to enhance the underglaze motif by creating a beautiful exterior surface. Underglaze does not vitrify like glaze, in order to have a shiny surface, a coat of glace over the underglaze is necessary.
Using a spray booth to spray glaze is another common application method. It requires a spray booth, air compressor and spray gun. The glaze consistency is usually thinner a glaze for dipping, in order to allow the glaze to flow freely from the spray gun. In a well-ventilated spray booth, the glaze is spayed onto the surface of the pot. This creates a very even coat. Often, the inside of a pot is coated with glaze by pouring and swirling the glaze around, while the exterior glaze is sprayed on. Lead glazes should never be applied with this method.