Underglaze or engobe is a pigmented compound that fires to a dull unshiney surface.
It is made from ground up/ powdered colored chemical compounds.
Underglaze has no silica [ sand ] in it to form a glass like shiney surface.
Subsequently, it is very stable and does not flow, drip or stick to anything it touches
when firing in the kiln.
A cover coat of clear glaze gives underglaze or engobe a shiny surface. Traditionally,
ceramics were not shiny. You can see an example of a very old bowl at the Los Angeles
County Museum of Art web site @
collectionsonline.lacma.org
The formed head is ready to underglaze when it is at least leatherhard.
[ Almost, completely dry; with some water still in the clay and little or no flexibility left.]
Typically, this could be as soon as the day after forming in any climate.
Bone dry clay is okay, too. Although, it is more difficult to make corrections
or use
sgrafitto
techniques when it is bone dry.
Underglazing is fast and fun.
The physical properties of underglaze are very “WYSIWYG”
[ What you see is what you get. ] The color you see is very close to
the color you get after it is over glazed with clear and fired. The underglaze brushes
on with the same ease as tempra paint. It is best to brush on light colors first. Dark colors
easily cover light colors. All colors require at least two layers or coats. It is best to
put each color directly on the clay with very little over painting. i.e.
Brushing brunette hair on a head with brown and then trying to change to blonde with a cover
coat of yellow is not desirable. It will not work. The reverse, however, will probably work.
[ Dark over light ]
The head at the right, had lines drawn into the clay with a pencil during the forming stages.
The lines gave the student borders for each color. One clear advantage to decorating on unfired
clay is the ability it scrape off undesirable features or color.
