Stains are mixtures of metalic oxides that have been fired and ground up
and combined to produce a variety of colors. Some metalic oxides are more
toxic than others.
Metals can be fluxes in glazes. If the Mayco clear glaze has a "frit" as
one of it's components, a stain containing copper carbonate can be a
significant problem in leaching of lead.
It's a good idea to have the MSDS sheets on all the raw chemical materials.
The MSDS sheets should tell you what chemicals are in the materials and
what the associated hazards are that go along with the use of that material.
If you are mixing Mason stains into your clear glaze make sure you use a
properly fitted respirator.
You can have Alfred University in New York test your glazes for leaching of
toxic materials. The tests run $10-40 dollars.
Dr. Roland Hale, Director
Alfred Analytical Laboratory
4964 Kenyon Road
Alfred Station, NY 14803