Very fine silicon carbide can be added to electric kiln-fired ceramic glazes to create glaze reduction. Copper red, for instance, can be made by adding 0.3% SiC, 0.3% copper oxide and 1% tin oxide to a clear base glaze. Fluid glazes that allow CO2 bubbles to escape give the best results.
For more information on silicon carbide, see the Digitalfire.com Reference Library of ceramic materials.