From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Method for applying a black finish to brasswork.
| Identifier | ExFiles\Box 38\6\ Scan151 | |
| Date | 12th January 1925 | |
| X. 3424. BLACK FINISH ON BRASSWORK. A method of blackening small brass parts, and one that is practically a standard method, may be given, particularly as it requires no special appliances. For this method a strong solution of nitrate of copper is prepared by dissolving scraps of copper in concentrated nitric acid until it can dissolve no more. This must be done in the open air by reason of the noxious and corrosive fumes produced by the chemical action. The clear liquid is decanted off after it has cooled and settled. The parts to be blackened are then cleaned in strong soda and well washed and then dried in saw-dust. They are then heated in a Bunsen burner (by securing to them a piece of wire for holding) to a temperature of 212 degrees Fahr. and dipped in the nitrate of copper, then heated again to dry off the solution. The process may then be repeated to obtain a sufficient deposit. The part may is then well brushed and dipped in ammonia. Finally the part is again warmed so that it is not too hot to hold and some olive oil rubbed over it with a leather. The oil is then dried off by heat. The results is a black surface that will resist any wear short of frequent rubbing, which is quite unnecessary. The worn condition of the black plating of the lamps that one notices on many smartly kept cars is due to thoughtlessness in appreciating that the black finish is very thin and that | ||