You would want to rust blue everything to be the same color. But small parts don't come out the same way and it's a pain. Nitre bluing is not the same color. Rust blue is a dark blue/Black depending on polish, method of application, length of rust time, carding frequency, style of carding and method to convert rust to black oxide. Nitre blue is a heat blue 550-700 degrees and it turns the color anywhere from straw to a purple-black. Most commonly an electric light blue. And it's polished much higher than a piece prepped for rust blue.
Ryan
