Rutile is the mineral name for natural crystals of titanium dioxide. In nature rutile is always contaminated by up to 15% other minerals (especially iron but also things like tantalum, niobium, chromium and tin). Rutile is considered an impure form of titanium. Rutile is used in welding rods and for this reason bags of rutile might have labels like "Welding Rod Titanate". Rutile is available in light calcined ceramic grade powder. In glazes it is generally better to use the ceramic grade since the decomposition of raw rutile during firing can be a source of glaze imperfections like pinholing. Rutile produces many crystalline, speckling, streaking, and mottling effects in glazes during cooling in the kiln and has been used in all types of colored glazes to enhance the surface character. It is thus highly prized by potters, many attractive variegated glazes are made using it.
