Hot dip Bluing

     Without getting into a historical overview of all the versions of bluing, suffice it to say that it is the oldest firearms finish and most popular in use on carbon steel firearms today. In my opinion, bluing is the finish that makes a firearm look like a firearm. Because it's a very dark, almost black finish, it does a good job covering or minimizing small flaws in metal finishing and preparation. The commercial bluing process is done by submerging the carefully prepped and degreased parts in a heated bath of water and bluing salts until the parts turn blue/black. The appearance of the blued steel can be varied from an eggshell matte texture (done by blasting with glass beads and high pressure air) to high polished blue (done by polishing with progressively finer grades of abrasives). The matte texture is normally applied to all the rounded surfaces and those that you want to have a non-reflective surface, while the flat surfaces are polished anywhere from about 400 grit up to 2,000 grit and beyond. Flat surfaces polished to that point and then blued have the appearance of looking into a bottle of ink. My bluing work is priced at 4 different levels of prep work. The only difference between them is how fine a grit the polishing is taken to. It's all done by hand, the hard way, never on a buffing wheel.
     Bluing is readily worn from use and easily rusted. A few dozen draws from a properly fitting leather holster and you'll probably be able to tell it, even if it didn't wear through to bare steel. Handle it with sweaty hands, then put it away without wiping it with an oily rag and your pretty blued gun will have a case of the "brown fuzzies" in a few days. This isn't to say that bluing isn't a valid choice for a finish for your pistol; just that bluing has some limitations. Wipe it down after handling and keep it out of kydex holsters and you can probably live in harmonious existence with a blued pistol. If you have "poison hands", carry concealed and keep the gun wet with sweat or live on a body of saltwater, bluing probably isn't the best choice.
     There are some limitations as to what materials are suitable for bluing. Aluminum parts will dissolve in a bluing bath. Stainless cannot be blued with the same baths used for normal bluing. There are some processes that will color stainless black, but they all have problems of one kind or another. Some steel alloys will not turn black, darkening to a plum color instead.

   Parkerizing

     Parkerizing has been around since before WW II and is still a process that delivers a useful finish today. The most common form of this finish is a deposit of manganese & phosphate, which are applied by soaking the parts in a heated bath. It must be done to parts that have been prepared by degreasing and sand or glass bead blasting. Parkerizing can only be done to carbon steel parts. The rule of thumb is if you can blue it, you should be able to Parkerize it. Parkerizing has a crystalline structure that will hold oils and waxes well. It varies in color between medium gray and charcoal black and has a sort of "soft" look to it. The old G.I. guns that had a greenish-gray color got that color from being coated with preservatives such as Cosmoline. The variation in color is due to differences in the base steel alloy and it's heat-treating and tempering. The color variation can occur on the same part, where a specific area was treated with induction hardening. A Parkerized gun is just a little more durable to abrasion than a blued gun, but is more rust resistant. Because it's been the finish on many of our military arms, it speaks to anyone that ever carried a U.S.G.I. M-1911.

   Sprayed Coatings

     Called "Spray & Bakes" by detractors, these coatings vary in quality from really awful to quite good. The process requires a bit more sophistication than simply hosing down your blaster with some "Gun Scrubber", squirting on some paint from an aerosol can and then sticking it in Mama's kitchen oven to dry, while supper's cooking. I've seen some jobs that I'm sure were done without disassembling the pistol.
     When it's properly done, it's a more durable black finish than either bluing or Parkerizing. Please don't assume that it's on par with hard chrome or electroless nickel; it's not. What it does do is to seal the gun's pores so that nothing can attack the base metal. This is a big plus for someone that (A) wants a black gun, (B) carry's concealed frequently (C) sweats (D) lives in an environment that has high humidity or salt water. The downside is that it's not as "bulletproof" as hard chrome. If you carry in a kydex holster, it will wear through at the corners. If you bang it into something hard, you may chip the finish. There are a couple of things worth mentioning at this point. Even when worn through to apparently bare steel, it's tendency to rust seems to be less likely than were it not coated. The other thing is that when bluing or Parkerizing wears through, they look better than a worn through spray coating finish does. Spray coatings must be applied to metal with a roughened up texture, such as bead or sand blasted. They will not adhere well to metal that has been polished first, because the mechanical bond is not strong enough.

   Hard Chrome

     As of this writing, hard chrome is the end-all, be-all firearms finish. Except for one thing: it isn't black. It is very hard, testing in the 70's in the Rockwell C scale. It is very wear resistant and durable because of this hardness. Applied properly, it bonds well to both carbon and stainless steel and has a degree of natural lubricity. Like bluing, different texturing techniques can be used during metal prep to give hard chrome differing degrees of gloss. Most frequently hard chrome is done in an all-over matte finish. Occasionally, you will see a combined texture of matte rounds and polished flats (the polishing is done to around 400 grit and called "brushed" usually). The combined texture hard chrome job needs to be reserved for a pistol with very good surfaces and true flats, as it will show any flaw easily. It can even be applied to metal that has been polished out to match the shine of the bumpers on your Dad's '59 Buick Roadmaster, should your tastes run in that direction.
     There are a few things to be aware of when you have your pistol chromed. The color is a bluish, whitish silver that will reveal any flaw in the base metal. While it is the most durable of all readily available firearms finishes, it is not impervious to damage. It can be rusted, if neglected. Banging it into something sharp and hard can scratch it. You can abrade the finish by enough draws in and out of a holster (of course, you will probably wear out a holster or two at the same time).

   Electroless Nickel

     Although it has some similarities to hard chrome, Electroless Nickel is a unique finish that holds it's own place in the firearms finishing world. Don't confuse this finish with Nickel electroplating. They are two very different processes that serve different purposes. Electroless nickel is a silver colored finish that has a golden cast to it, when compared to hard chrome. Electroless nickel provides a very uniform thickness of coating on all surfaces of the part being plated, where as nickel electroplating is typically heavy on the corners and thin on the flats. Electroless nickel doesn't test quite as hard as hard chrome on the Rockwell C scale, but is a good bit more corrosion resistant. It can be used as an undercoat to enhance the rust resistance of hard chrome. It can be applied to aluminum frames to allow hard chrome to adhere.

   Anodizing

     Aluminum has to have some help, in order to last as a firearm frame. The traditional way to increase the surface hardness of aluminum is to anodize the frame. A series of chemical baths with a small electric current will create a very thin skin of aluminum oxide that is much harder than the base alloy in it's natural state. Introduction of a dye during the process can finish the part in a variety of different colors, with black being the most often encountered.

   Combination Finishes

     One of the old standbys in custom 1911 finishes has been the two-tone look; a blued top end and a hard chrome bottom. This combination is unique, attractive and fairly practical due to the frame assembly having the attributes of being durable and rust resistant, while the slide assembly is more glare proof.