Spectrum's Underglaze Base is formulated as a base media for preparing your own underglaze colors similar to the 500 series underglazes. The 1050 Underglaze Base has some frit in it, which acts as a flux to help the stain be a compatible fit with either greenware or bisque. It also has various additives, which keep the frit and stain suspended and make it brush on smoothly and easily.
It is lead free, non-toxic and dinnerware safe when covered by a dinnerware safe clear glaze.
In order to achieve an underglaze of a strength similar to the 500 series Underglazes, you should mix 1 part of dry powder ceramic stain to 2 parts wet underglaze base by weight. For example, if you put half a pint (8 ounces or 228 grams) of 1050 underglaze base in a container, you should mix 1/4 pound (114 gram) of stain in this.
This recommendation is only a general guideline as the strengths of different color stains vary and you should test colors, particularly the first time you mix them, to determine the correct strength for your application.
One Pint (16 oz.)