Manila Copal

Copal is a hard diterpene resin - the hardest being the fossile ones. The term "Copal" denotes a variety of different countries of origin and provenance; they usually form hard oily varnishes, by means of a somewhat complicated cooking process which renders them soluble in oils and turpentine. In the Middle Ages, copal was confused with amber. Often used as an insulating varnish over tempera underpaintings.