It is an oleo-resin (see resin) obtained through the exudation of a conifer. Its consistence is viscous and it is yellowish in colour, with a strong aromatic odor. Known since the end of Antiquity, it was used in the composition of varnishes and mediums employed in the technique of glazing. In restoration it is used in the composition of the mixture for lining, to which it gives elasticity and softness.