Case color HARDENING is a process by which carbon is added to a low carbon steel by heating the steel to a specific temperature while surrounded by carbon. In the case of firearms that carbon was provided by bone and charcoal. The colors are produced by the gases released when the steel is quenched in water. It is not considered a heat treating process because the steel is not hardened throughout, but only a few thousanths of an inch deep, typically .005 to .010 deep. Hence the term CASE hardening meaning it is only the outside casing of the steel. Another method of case hardening was done by using CYANIDE. This method would produce the type of finish seen on Delgreco restorations of Parkers or the type found on tools made by Starrett. In any case , case hardening is a way of providing a very hard outside surface to low carbon steel while keeping the inner mass malleable. It is done everyday all over the world as a manufacturing process. However as in any het treating process anything can go wrong if the process uis not followed correctly and the material is allowed to get too hot these things occur all the time in the manufacturing world and the results could be broken parts if they are allowed to get out of the plant instead of scrapped after the error was discovered
