tech notes: underglaze/glaze

CLAYS, GLAZES and UNDERGLAZES

SILICA CONTENT: clay, glaze and under glaze all contain

UNDERGLAZE ….is a colored slip
•    Can be can be applied to green ware or bisque ware
•    The commercial under glazes that we are using in the lab contain no lead or heavy metals
•    Should be applied thickly, read the bottles for suggested thickness
•    Can be mixed with glaze for varied results.
•    Can be mixed together like paints to create a greater range of colors
•    Can be watered down for watery washes of color.
•    Can be used on the bottoms of works.
•    Some under glazes *MAY* begin to vitrify at our clay body’s maturing temperature (CONE 6), so be careful and always make a test tile first.

GLAZE, the glassy coating that people use to make works shiny or waterproof has a much higher concentration of silica in it. Applied after bisque firing the piece.

TEST TILES
•    are small pieces of clay used to test glaze materials before you use them on your larger finished piece (and potentially ruin your work).

•    You should always use a test tile that replicates the texture of the piece that you will ultimately be glazing.

MIXING GLAZES and APPLYING GLAZES
•    When mixing your own glazes from powdered chemicals (in Ceramics II for instance) you will always work under the vent and always wear a respirator and rubber surgical gloves.

•    NO eating in the studio. You may have coffee out of a lidded container that is kept away from glazing areas.

•    Always wash your hands after handling glaze materials and before you eat.

ALWAYS MAKE A TEST TILE FIRST