From FORMULAS, PROCESSES AND TRADE SECRETS, 1937 ed., The Norman W. Henley Publishing Co., N.Y.

JAPAN BLACK - "The following is a good japan black for metal surfaces: Take 12 ounces of amber and 2 ounces of asphaltum. Fuse by heat, and add 1/2 pint boiled oil and 2 ounces of rosin. When cooling add 16 ounces of oil of turpentine."