Copal Varnishes. - Best Body Copal Varnish.2 - Fuse 8 lbs. of fine African gum copal, add 2 gallons clarified oil. Boil very slowly for four or five hours till quite stringy, and mix with 31/2 gallons turpentine.
This is used for the body part of coaches, and for other objects intended to be polished.
The above makes the palest and best copal varnish, possessing great fluidity and pliability, but it is very slow in drying, and, for months, is too soft to polish.
Driers are therefore added, but they are injurious (see p. 431).
To avoid the use of driers, gum aninie is used instead of copal, but it is less durable and becomes darker by age.
The copal and anime varnishes are sometimes mixed; one pot of the latter to two of the former for a moderately quick drying varnish of good quality, and two pots of the anime to one of the copal for quicker drying varnish of common quality.
Best Pale Carriage Copal Varnish.3 - Fuse 8 lbs. of second sorted African copal, add 21/2 gallons of clarified oil. Boil slowly together for 4 or 5 hours until quite stringy; add 51/2 gallons of turpentine mixed with 1/4 lb. dried copperas, 1/4 lb. litharge; strain, and pour off.
3 Ure, Spon.
In order to hasten drying, mix with the above while hot 8 lbs. of second sorted gum anime, 21/2 gallons clarified oil, 1/4 lb. dried sugar lead, 1/4 lb. litharge, 51/2 gallons of turpentine.
This varnish will, if well boiled, dry hard in 4 hours in summer or 6 in winter. Some copal varnish takes, however, 12 hours to dry.
This varnish is used for carriages, and also in house painting for the best grained work, as it dries well and has a good gloss.
A stronger varnish is made for carriages, known as Best Body Copal Varnish.
8 lbs. of second sorted gum anime, 23/4 gallons fine clarified oil, 51/4 gallons turpentine, 1/4 lb. litharge, 1/4 lb. dried sugar of lead, 1/4 lb. dried copperas, boiled and mixed as before. Used for varnishing black japan or dark house painting.1
Pour 2 gallons of hot clarified oil on 6 lbs. of very pale transparent amber. Boil till strongly stringy, and mix with 4 gallons turpentine. This will work very well, be very hard, and the most durable of all varnishes, and improves other copal varnishes when mixed with them; but it dries very slowly, and is but little used on account of its expense.2
White Coburg Varnish is of a very pale colour, dries in about 10 hours, and in a few days is hard enough to polish.
Wainscot Varnish is made of 8 lbs. gum anime (second quality), 3 gallons clarified oil, 1/4 lb. litharge, 1/2 lb. sugar of lead, 1/4 lb. copperas, boiled together till strongly stringy, and then mixed with 51/2 gallons turpentine.
It may be darkened by adding a little gold size.
This varnish dries in two hours in summer, and is used chiefly for house painting and japanning.2
Oak varnish is used for common work. It dries generally in about 10 hours, though some is made to dry in half the time, and known as Quick Oak Varnish; another variety is called Hard Oak Varnish, and is used for seats.4
"Copal Varnish (spirit). - By slow heat in an iron pot melt 1/2 lb. of powdered copal gum, 2 oz. of balsam of copivi, previously heated and added. When melted, remove from the fire and pour in 10 oz. of spirits of turpentine, also previously warmed. Copal will more easily melt by powdering the crude gum, and let it stand for a time covered loosely." 3
White Hard Spirit Varnish may be made by dissolving 31/2 lbs. gum sandarach in 1 gallon spirits of wine; when solution is complete adding 1 pint of pale turpentine and shaking well together.
Brown Hard Spirit Varnish is made like the white, but shellac is substituted for the sandarach. It will bear polishing.