To obtain a dense black stain for wood, boil together in an old iron pot 1 gal. of strong vinegar, 2 lb. of extract of logwood, 1/2 lb. of green copperas, 2 oz. of China blue, and 2 oz. of crushed nut-galls; then add 1/2pt. of acetate of iron, made by steeping rusty nails or iron turnings in common vinegar. Apply liberally with a brush. The wood must be perfectly free from grease and glue, and should be handled as little as possible.