This section is from the book "The Tinman's Manual And Builder's And Mechanic's Handbook", by Isaac Ridler Butt. Also available from Amazon: The Tinman's Manual And Builder's And Mechanic's Handbook.
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.
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 130 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 mis-i. Boiling oil of turpentine combines very readily with fused copal; and, in some cases, it would probably be preferable to com-mence 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.
1. Melt in an iron pan at a slow heat, copal gum, powdered, eight parts, and add balsam copaiva, previously warmed, two parts. Then remove from the fire, and add spirits of turpentine, also warmed beforehand, ten parts, to give the necessary consistence. 2. Prepared gum copal ten parts, gum mastic two parts, finely powdered, are mixed with white turpentine and boiled linseed oil, of each one part, at a slow heat, and with spirits of turpentine twenty parts. 3. Prepared gum-copal ten parts, white turpentine two parts, dissolve in spirits of turpentine.
Gum-copal is prepared or made more soluble in spirits of turpentine, by melting the powdered crude gum, afterwards again powdering, and allowing to stand for some time loosely covered.
Copal, fused, fourteen pounds; linseed oil, hot, one gallon; turpentine, hot, three gallons. Properly boiled, such a varnish will dry in ten minutes.
Damma resin, one pound; spirits of turpentine, two pounds; camphor, two hundred grains. Digest the mixture for twenty-four hours. The decanted portion is fit for immediate use.
Oil of turpentine, one pound; bees' wax, two ounces; colophony, one drachm.
1. Pounded and oxidixed copal, twenty-four parts; spirit of turpentine, forty parts; camphor, one part.-2. Flexible Copal Varnish. Copal in powder, sixteen parts; camphor, two parts; oil of lavender, ninety parts,
Dissolve the camphor in the oil, heat the latter, and stir in the copal in successive portions until complete solution takes place. Thin with sufficient turpentine to make it of proper consistence.
This is intended for the body parts of coaches and other similar vehicles, intended for polishing. Fuse eight lbs. of fine African gum copal, and two gallons of clarified oil, boil it very slowly for four or five hours, until quite stringy, mix with three gallons and a half of turpentine; strain off and pour it into a cistern. If this is too slow in drying, coach-makers, painters and varnish-makers have introduced to two pots of the preceding varnish, one made as follows: eight lbs. of fine pale gum-anime, two gallons of clarified oil and three and a half gallons of turpentine. To be boiled four hours.
Digest or shake finely powdered gum copal four parts, and gum camphor one part, with ether to form a semi-fluid mass, and then digest with a sufficient quantity of alcohol.
Sandarach, 250 parts; mastic, in tears, 64; elemi resin, 32; turpentine, 64; alcohol of 85 per cent, 1000 parts, by measure. The turpentine is to be added after the resins are dissolved. This is a brilliant varnish, but not so hard as to bear polishing.