No, Wade, there are at least three general types. First there is the Rust Blue, talked about here, then there is the modern type used commercially today using chemical salts, no rust involved, and then there is charcoal bluing, where the parts/barrel is sealed, and buried in a charcoal fire, and the metal is cooked blue. The archives have some comments, and examples of this method. Also I guess there also is the touch up cold blue.
bill