Black Varnish.
Asphaltum, dissolved in Spirits or Oil of Turpentine.—The asphaltum may be coarsely pulverized and put into a bottle containing the turpentine, and in a few hours, if it be occasionally shaken, it will be dissolved and ready for use. It should be of about the consistency of thick paste.
I use the above, but will now give two more compositions, for any who may wish to adopt them:
Black Japan.—Boil together a gallon of boiled linseed oil, 8 ounces of amber, and 3 ounces of asphaltum. When sufficiently cool, thin it with oil of turpentine.
Brunswick Black.—Melt 4 lbs. of asphaltum, add 2 lbs. of hot boiled linseed oil, and when sufficiently cool, add a gallon of oil of turpentine.
The following is from Humphrey's Journal, Vol. viii, number 16.
Black Varnish.—I generally purchase this from the dealer; but I have made an article which answered the purpose well, by dissolving pulverized asphaltum in spirits of turpentine. Any of the black varnishes can be improved by the addition of a little bees'-wax to it. It is less liable to crack and gives an improved gloss.
Before closing this chapter, it has been thought advisable to remark, that one of the most important departments of Photography is the practice of its chemistry. Many of the annoying failures experienced by those who are just engaging in the practice of the art, arise from the want of good and pure chemical agents, and the most certain way to avoid this, is to purchase them only from persons who thoroughly understand both their nature and mode of application. As many who may read this work might wish to know the prices of the various articles employed in the practice of the processes given, they can be informed by addressing the author, who will furnish them with a printed Price List.