I would just like to add something to the discussion I have found over the many years I have been bluing and browning gun barrels. On guns made some 30 years before 1900 and up to the 1950s, barrel rust blueing always went well and with very little trouble even with changing rusting solutions. Then after the 1950s steel used in barrels started to have small amounts of Chrome Nickel and Cobalt added to name just a few, this started to cause me problems and the need to change rust bluing solutions to make things happen correctly. Though I did find that one bluing solution worked well every time and it stayed that way until I hung up the rubber gloves and let the younger generation take up the art of bluing and browning.
The bluing solution is named after the American gunsmith Hervey lovell it can be found in Angier's under rapid bluing solutions though it uses enough Mercuric Chloride in its makeup to kill an Elephant.
