Artists should mostly apply glaze to pottery pieces that have been "bisque" fired. These pieces are already in their final form, and glaze is added as a final decorative step. Most glazes are opaque or semi-transparent. Artists who want to cover an entire piece with a singular color of glaze should put on two or three coats at least to ensure complete coverage. Glaze should be applied evenly, as most chunks or heavy brushstrokes will appear in the finished piece. Artists can apply glaze in a few different ways. They can dip entire pieces into a pot of glaze, pour glaze over a piece or apply glaze through painting and spraying methods.
Underglaze is often used for decorative purposes. Artists can paint underglaze directly onto the surface of unfinished, or "bisque" fired pottery. The underglaze can be applied into a particular image or pattern, or can just be of a different color than the regular glaze layer. A transparent wet glaze can be applied on top of the underglaze before the piece is put back into the kiln for the final time.
Potters and sculptors can combine different glazes in unique ways to come up with interesting patterns and designs for their ceramic pieces. For example, artists can use a technique called sponging. Sponging involves first dipping a piece into one glaze color and then going over that layer with a sea sponge dipped into another color of glaze. Another glazing technique is etching, which involves submerging a piece first into one layer of glaze, and then into another. Once both glazes are applied, the artist can use an open-ended wire tool to etch away pieces of the first layer of glaze, leaving the second layer to poke through in a planned design or pattern.
Non-leaded and leaded glazes should not be mixed together on one piece. When these two combine, they can cause the ceramic piece to crack or shatter. Glaze melts when it is fired. It is important to apply wax underneath a piece of pottery so that the glaze does not melt it to the kiln during firing.