Spectrum – Raku - 881 - Oxblood Raku - PintSpectrum Raku glazes were developed for firing in either electric or gas kilns. The firing process is described below. Eleven of the Raku glazes are lead free and non toxic (850,851,854,856,871,872,873,874,875,877,878). All of the rest are lead free, but are over the threshold limit for copper and are therefore not non toxic in the liquid state. Spectrum liquid glazes are formulated for brushing application. They can also be poured or dipped on