Glass grinding pastes are used to sand and polish glass. Grinding glass is a cold process and is important in removing devitrification--white scum that sometimes forms on the surface of glass when glass is held at too high a temperature for too long during kiln firing. It also removes rough edges from glass. Glass grinding and polishing are usually the final steps in producing kiln-formed glass objects. The same process, however, can be used to repair scratched glass. Although there are many commercial glass grinding pastes on the market, artists, home hobbyists and homeowners with damaged glass goods often like to mix their own pastes to save money and to create specialised products tailored to the needs of particular types of glass.
Place silicon carbide in a mixing bowl. Silicon carbide can be purchased at most stores selling supplies for ceramics, stained glass or fused glass.
Add water to silicon carbide. Mix the silicon carbide with the water until you form a slurry the thickness of paste. The amount of water you need will depend on your altitude and the atmospheric conditions in your area. Take notes as you work so you can replicate your results in the future.
Place the silicon carbide paste on a glass grinding wheel to sand and polish the glass. If you do not have a glass grinding wheel, work the glass grinding paste into the material by hand by placing the silicon carbide paste on a felt rag and rubbing it into the glass using medium pressure in a circular motion.
Rinse the glass with water to remove all grinding material.
Repeat with increasingly finer grits of glass grinding paste until the scratch is removed or the glass is polished. To make finer grits of glass grinding paste, substitute pumice or cerium oxide for the silicon carbide. Pumice and cerium oxide can be purchased at most stores selling supplies for stained glass or fused glass.
Wear a dust mask when working with abrasives to protect your lungs from particulates. Never sand glass dry. Keep glass well lubricated when sanding, grinding and polishing to reduce airborne dust containing glass shards.