(taken from Photographic Facts and Formulas - 5th printing - Wall and Jordan
BLACK FOR WOOD AND METAL
Use vegetable black mixed with terebene or turpentine. When used on the inside of the bellows, the black is made into a stiff paste with raw linseed oil and then thinned down with turpentine.
BLACK FOR CAMERAS
This may be used for wood or leather, inside or out.
Nigrosine, spirit soluble . . . 2.5g
Bismarck Brown . . . 0.65g
Alcohol . . . 3.0cc
Aniline . . . 29.0cc
Heat the dyes with the alcohol until dissolved. Then add the aniline and apply with a brush and dry before a fire or in sunlight. For a dead mat varnish, lampblack may be rubbed up with gold size or shellac varnish, using as little of the liquid as possible. Then thin down with turpentine.
TO BLACKEN ALUMINUM
Clean perfectly free from grease by washing in soda solution, wash well and immerse in . . .
Ferrous sulphate . . . 1 part
Arsenious Acid . . . 1 part
Hydrochloric Acid . . . 12 parts
Water . . . 12 parts
When the color is deep enough, dry with fine sawdust, and then lacquer. This solution is intensely poisonous.
I have not used these formulas in any way. Just passing them along to APUG.