1. Copal Varnishes

1. Oil of turpentine one pint, set the bottle in a water bath, and add in small portions at a time, three ounces of powdered copal that has been previously melted by a gentle heat, and dropped into water; in a few days decant the clear. Dries slowly, but is very pale and durable. Used for pictures, etc. 2. Pale hard copal two pounds; fuse, add hot drying oil one pint, boil as before directed, and thin with oil of turpentine three pints, or as much as sufficient. Very pale. Dries hard in 12 to 24 hours. 3. Clearest and palest African copal eight pounds; fuse, add hot and pale drying oil two gallons, boil till it strings strongly, cool a little, and thin with hot rectified oil of turpentine three gallons, and immediately strain into the store can. Very fine. Both the above are used for pictures. 4. Coarsely-powdered copal and glass, of each four ounces, alcohol of 90 per cent one pint, camphor one-half ounce; heat it in a water-bath so that the bubbles may be counted as they rise, observing frequently to stir the mixture; when cold decant the clear. Used for pictures. 5. Copal melted and dropped into water three ounces, gum sandarach six ounces, mastic and Chio turpentine of each two and one-half ounces, powdered glass four ounces, alcohol of 85 per cent, one quart; dissolve by a gentle heat. Used for metal, chairs, etc.

All copal varnishes are hard and durable, though less so than those made of amber, but they have the advantage over the latter of being paler. They are applied on coaches, pictures, polished metal, wood, and other objects requiring good durable varnish.

2. Copal Varnish

Hard copal, 300 parts! drying linseed or nut oil, from 125 to 250 parts; oil of turpentine, 500; these three substances are to be put into three separate vessels; the copal is to be fused by a somewhat sudden application of heat; the drying oil is to be heated to a temperature a little under ebullition, and is to be added by small portions at a time to the melted copal. When this combination is made, and the heat a little abated, the essence of turpentine, likewise previously heated, is to be introduced by degrees; some of the volatile oil will be dissipated at first, but more being added, the union will take place. Great care must be taken to prevent the turpentine vapor from catching fire, which might occasion serious accidents to the operator. When the varnish is made and has cooled down to about 180 degrees of Fah., it may be strained through a filter, to separate the impurities and undissolved copal. Almost all varnish makers think it indispensable to combine the drying oil with the copal before adding the oil of turpentine, but in this they are mistaken. Boiling oil of turpentine combines very readily with fused copal; and, in some cases, it would probably be preferable to commence the operation with it, adding it in successive small quantities. Indeed, the whitest copal varnish can be made only in this way; for if the drying oil has been heated to nearly its boiling point, it becomes colored, and darkens the varnish.

This varnish improves in clearness by keeping. Its consistence may be varied by varying the proportions of the ingredients within moderate limits. Good varnish, applied in summer, should become so dry in twenty-four hours that the dust will not stick to it nor receive an impression from the fingers. To render it sufficiently dry and hard for polishing, it must be subjected for several days to the heat of a stove.