Steve;

The Metals Handbook could also be considered to lack specifics. After an introductory paragraph, it continues;

"Various types of black finish can be secured. these depend principally upon the finish of the part before the special treatment is given. Cold drawn or highly polished parts will take a glossy black finish. Parts made from ordinary stampings will have a somewhat duller finish, while work which has been sand blasted prior to applying this treatment will have a black matte-like finish.

While not an entirely rust preventative coating, this finish acts as a retardent to the formation of rust.

To apply the gun-metal or carbonia finish, the work is placed loosely in a retort with a small amount of charred bone and heated to 700-800F. After the articles are thoroughly oxidized the temperature is allowed to drop to about 650F, when a mixture of bone and 1 or 2 tablespoonfuls of carbonia oil are added. Heating is then continued for a period of several hours. When the work comes from the retort it is a dull grayish-black and by dipping in sperm oil or tumbling in oily cork a uniform black finish is secured.

If the temperatures given will temper too much, a temperature as low as 500F can be used, but this lower temperature requires a longer time at heat to color the articles and the color is not so lasting as the color produced at the higher heats.

Gun- metal or carbonia finish may be applied to articles which have first been nitrided, resulting in a pleasing finish resistant to rusting and retaining the surface hardness on the articles, since these coloring temperatures do not temper the nitrided articles.

When a rotary retort is used and when the work is of such a nature that the slow rotation of the retort would cause scratches or in any way mar the finish, special fixtures may be used to hold the work in place. These fixtures are usually necessary only when large parts are to be finished."

As I said, a lack of specifics; 1 or 2 tablespoons in how much bone? etc., but, maybe there's another clue for those who are more knowledgeable than me.

I was in your part of the world this time last year, during a five week visit to the U.S. I have single shot rifle friends in Cody so visited them and spent a few days around Big Timber, Livingston and Bozeman. I've seen illustrations of your work and did consider trying to make contact.

Frank,
SWCA 2052
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