[CalvinMD]

How brave are you? Years ago I blued guns with a solution of water, Ammonium nitrate and lye. after more than a few years and the finish is still a pretty dark lustrous blue. Be aware of the dangers of using this type of hot bath and am equipped to safely handle the parts and chemicals with gloves and eye protection. Heres the formula utilizing Ammonium nitrate that you can get at a fertilizer store...if you want top results take your time prepping and during the process..you should do it outdoors in an area protected from wind so you have no fume or fire hazard..I do it on a old Coleman camp stove
-------------------------------------------------------------------------------Basic Formula

5 pounds lye
2 1/2 pounds ammonium nitrate
per gallon of water

Heat mixture until working temperature 285-295 degrees, soak 15-40 minutes depending on the hardness of the steel.
after removing parts from solution remove and dip into pot of very hot water to rinse...then let dry from evaporation..then a lil pan of cheap motor oil
Well prepared (polished and cleaned) parts will come out with a durable black finish that can take a wire brush test without damage.
IMPORTANT!: Have lots of ventilation when adding the ammonium nitrate as there are a lot of ammonia fumes.
NOTE: This Will eat solder or lead so know what you the parts you are planning to blue are made of.

If you attempt this YOU DO THIS at YOUR own risk!!! I had no trouble but theres lots of info how to do this in many places...read as much as possible before attempting until you are confident with being able to perform the process