IMHO, hot tank bluing is NOT a home project. It requires three bluing tanks (a degreaser, a bluing tank, and a rinse tank, all with electric or gas heating. You also need an emergency shower area with a heavy water flow in case hot salts splash on you. Plus heavy rubber boots, a rubber apron, face/eye protection, and so forth. It is a damned dangerous business and not something you do in the kitchen unless you have a very unusual kitchen.
Again, IMHO, none of the "cold" blues are much good. No matter what the sellers say, cold blues only give a temporary color that comes off easily. Rust blue is OK, but requires extensive preparation and also needs a heated tank large enough to boil the gun during applications, and a rinse tank that does not need to be heated.
In short, unless you want to set up in business, have bluing done by a professional who is set up to do it.
Note: Some people are promoting "home made" bluing salts for "easy use." The salts are the same as those bought from gun shop suppliers, so the above applies to them as well, no matter what claims are made about easy DIY. Plus, the ingredients, if available, will usually cost MORE than the cost of commercial bluing salts and may not do as good a job if the chemicals are not as strong or are not mixed properly.
Jim
