As other soft resins are sometimes substituted for mastic, so inferior hard resins are sometimes employed in the place of copal in the composition of varnishes celebrated as copal varnishes; but the simple solution of pure picked copal made by triturating and digesting it in oil of turpentine, as recommended by Mr. Cornelius Varley, is of more certain effect in painting and varnishing of pictures, and superior to mastic varnish in the permanence of its colours; - as a simple vehicle, it is nevertheless deficient of the tenacity and flexibility which render linseed oil so essential in painting; combined, however, with linseed oil and oil of turpentine, copal varnish affords a vehicle superior in texture, strength, and durability to mastic and its macgilp, though in its application it is a less attractive instrument, and of more difficult management: it is, therefore, a desideratum with the artist to form a macgilp of copal, which would stand up with the flimsy firmness of that of mastic; till which can be done, be must be content to mix it as above; for linseed oil is essential to prevent its cracking. The mixture of copal varnish and linseed oil is best effected by the medium of oil of turpentine, and for this purpose heat is sometimes requisite: strong copal varnish and oil of turpentine in equal portions with one-sixth of drying oil mixed together, hot, afford this vehicle; and if about an eighth of pure bees-wax be melted into it, it will enable the vehicle to keep its place in the manner of macgilp.