ill have alook over there Maca .
just a bit more description on bluing than the other post -great what you can find on line and educate yourself with!!
Hot salts bluing.
This is todays bluing system as used by all gun makers.
The metal is boiled in a tank of chemicals which gives it a black-blue color.
This is actually "oxidation" or a controlled form of RUST, which has a blue-black color and is smooth.
Rust blue.
Rust blue is a process in which the metal is caused to rust with a chemical that gives a blue in color instead of the usual rust-red color.
The parts are boiled in water, removed and swabbed with the chemical.
The parts are allowed to rust, then "carded" off with steel wool. At this point the metal has a grayish streaked color.
As the process is continued the color deepens and darkens into a satin blue.
There are a number of processes in which rust blue can be done.
Rust blue has a more satin finish that's blue but not the glossy blue of other methods.
It is a durable, tough blue, and is one of the few methods by which double guns with soft soldered barrels can be blued.
Due to the amount of time and hand labor, rust blue is expensive.
Carbona blue.
Carbona is an advanced form of heat bluing.
This is the process many gun companies used years ago, especially Colt.
The cleaned parts are put in steel drums along with a mix of various materials, including charred leather, charcoal, bone meal, and other often "secret" materials, then the air-tight drums are put in a furnace at carefully controlled temps.
The materials give off a gas that drives out moisture and air, and the metal takes on a deep shiny black-blue color.
Heat bluing.
There are a good number of heat bluing methods, known by various names like "Fire Bluing". These are basically simply variations of heating the metal until it changes color.
The simplest method is to just polish the metal, clean it then heat it up.
As the metal heats, it starts to change colors, first a light yellow "straw" to a darker golden, to a brown, then purple, and finally a brilliant blue.
Most heat blues are very colorful, but very delicate and easily worn off.
All heat blues must take into account the hardness and temper of the metal. Some guns parts should not be heat blued.
Cold blue.
Cold bluing is a commercial chemical that works for touching up worn areas or scratches.
It's not very durable, tends to turn brown as it ages, and usually doesn't work well for large areas.
When used to blue a large area, it tends to give a streaked, cloudy gray-blue color.
Nitre Blue.
This is another heat blue method, only using a salts compound that melts when heated.
When the metal is submerged in the liquid hot salts, it changes color like heat bluing, from a light straw to a brilliant blue.
Again, nitre bluing is rather delicate.
Some people have done nitre bluing using stump remover chemical from the hardware store.
Charcoal bluing.
Simply another name for a variation of Carbona bluing.
There are other methods, all of which are variations of the above methods.
They all use either a heat system to heat the metal until it changes color, or a chemical that causes the metal to rust with a blue or blue-black color.
With all these systems, the color and how shiny the finish is depends entirely on how well the metal is polished BEFORE the bluing process.
As example, the only real difference between the Ruger's satin black color and the deep, dark blue mirror-like finish of the 1950's Python was the degree of polishing the metal received before the metal was put into the hot salts bluing tanks.
