Dragon's blood (resin)

A transparent, resinous exudation, red in color, derived from several plants in 4 genera, having in common the primary red coloring component dracorubin. Dragon's blood is available as red sticks, cakes, or as a powder, and was traded as early as Roman times. It is used medicinally as an astringent, as a red colorant in medieval manuscript illuminations, to stain varnishes for violins, as a colorant for plaster, marble, and paints, and as a resist in photoengraving to protect zinc plates from acid. The red color is fugitive when exposed to light and air, but may be partially protected by a resin film layer.