Yes Paul, any Brown will turn blue/black if boiled, providing it hasn't been sealed. The higher the polish of the metal, the bluer it will tend to look. The high polish also requires more applications of brown, then boil, with shorter times between app's to keep the pitting at a minimum. I have an engraved lock plate I just got back from Jerry Rice, that I'm going to rust blue, then work back to highlight the engraving. I'l take and post some pic's. of the process.
Bill