Today, most underglazes on the market are formulated more like engobes. They are created using fritted material, which reduces shrinkage and allows them to be applied to bisqueware. (In some cases, they can be applied to both greenware and bisqueware.) Besides liquid underglazes, there are increasing options available for underglaze application. These include underglaze pencils, crayons, chalk, and semi-moist pads which can be used like watercolors.
Speedball Liquid Underglazes: A good all-around liquid underglaze. Amaco Semi-Moist Underglaze Pans: Concentrated underglaze in pans that handles much like watercolors. Amaco Underglaze Crayons: A wonderful way to draw on your pottery.
Slip can be used in a wide number of techniques, from simple brushed on patterns to the bas-relief embellishments of paste-on-paste. If you are using raw oxides or carbonates to make your own stains, be sure to use a respirator and rubber gloves as you work with them. Find out which raw materials are hazardous, and how to handle them safely.