Copal varnish is made as follows: Pale African copal, 7 pounds; fuse; add clarified linseed oil, one-half gallon; boil for 5 minutes. Remove it into the open air, and add boiling oil of turpentine, 3 gallons; mix well; strain it into the cistern and cover it up immediately. This is used to varnish furniture, and by japanners, coachmakers, etc. Dries in 15 minutes, and may be polished as soon as hard.
A good varnish for coating wood and iron is made by placing 3 pounds powdered resin in a receptacle, adding to same 2 1/2 pints spirits of turpentine, shaking well and allowing same to stand, shaking from time to time, for two days. After the elapse of two days, 5 quarts of boiled linseed oil are to be added, and the whole shaken together. Then decant the clear portion, reducing same with spirits of turpentine, in order to acquire the right consistency.
Rub to a fine powder 30 parts of crystallized acetate of copper, and leave it in a thin layer on porcelain for a few days in a moderately warm place, to drive off the water of crystallization and a portion of the acetic acid. Rub the bright brown powder that is left with a small quantity of turpentine, and add it with constant stirring to one hundred parts of fine copal varnish heated to 167 degrees F. If the acetic acid was sufficiently finely powdered, it will dissolve on stirring it about a quarter of an hour. Pour the varnish into a glass vessel and set aside for a few days, with occasional shaking. The varnish is dark green. Four or five applications to tinned iron give a fine green, lustrous tint. If heat is applied two coats will give greenish, yellow, dark yellow, orange, or reddish brown tints, according to the temperature. The source of heat may be an oven or an equally heated iron plate. Success depends on the uniform application of the varnish and the heat.
A varnish for iron is made by mixing, when warmed in an iron kettle, 1/2 pound powdered resin, 1/2 pound asphalt and 2 pounds tar oil. The mixture must be dissolved and care must be taken to prevent any contact of same with the flame.
A varnish for iron patterns is made by dropping strong sulphuric acid drop by drop into oil of turpentine. This will cause a precipitation in the oil of turpentine of a syrupy nature. The acid should be added until the precipitation no longer forms. The liquid is then poured out and the syrup washed, when it is ready for application. The iron to be varnished is to be heated to a luke-warm heat and after the application of the varnish allowed to dry.
White lava varnish is used to preserve polished edges from rusting and at the same time not detract from their appearance. Also white varnish may be used; or dissolve as much white resin in one-half pint of turpentine as it will take, and apply with a paint brush.