Optical polishing pitch from Meller Optics is available in five different grades

Gugolz Optical Polishing Pitch is offered in five grades for polishing CaF₂, germanium, quartz, ZnSe, ZnS, silicon, and other materials. Made from an all-natural wood resin, it has melting points from 52° to 87°C. Users can exactly match the pitch to their optical substrate without screening, filtering, and mixing additives.
Meller Optics
Providence, RI
www.melleroptics.com