Der Ami. Rust bluing is exactly what it says. Slow rust bluing is only slow because it takes time for the rust to form. There are rust blue formulas that will rust the metal in seconds or minutes, these mixtures where instant or rapid rust bluing solutions. You do not see these rusting solutions today because of there high toxicity and high cost due to difficulty in obtaining all the constituents. This method of rust bluing had major advantages as far as the gun trade was concerned having extremely fast turnaround and the mixtures could be used to instantly touch up worn blue sections in barrels. I do still have a pint of this rapid solution for my own personal use. I do think that if people are interested in the art of bluing and browning the best investment people can make is purchase a copy of "Firearm Bluing and
Browning " by R,H. Angier an old book but thankfully always being re printed.
