If you want to blue try this it sound very inexpensive. I have not tried it myself. I found it on the web some where.
I’ve never been one to like using any of the various cold bluing solutions, as the finish is both very temporal and lacking depth and color as well. So, what are the alternatives for the home hobbyist? My choice is simple, the deep, rich luster of niterbluing! The same process that used to make the deep blue/black finish found on fine custom European guns from a lifetime ago. Yes, yes, I know that I said a reasonable alternative for the home hobbyist, and that’s exactly what old-world niter-bluing can be! I hope I have your attention by this time, as when I first started doing niter bluing I was so excited that I simply couldn’t wait for my first project! It’s really too simple, and I can’t understand how in the world so many gallons of inferior cold-bluing solution are marketed every year when niter-bluing is so simple and so inexpensive.
Inexpensive? Yes, it surely is! Of course it isn’t if you’re looking through those high-priced specialty gunsmithing supply catalogs. Just the bluing salts alone will set a person back about fifty bucks, not to mention the specialty tanks to use the solutions! However, niter-bluing uses nothing except potassium nitrate for its active ingredient, and potassium nitrate in a suitably pure form is as far away as the local hardware store, nursery supply shop or home improvement mart! It’s called stump-remover, and it sells for about two dollars per one pound bottle of powdered potassium nitrate! For my purposes, a simple standard sheet-metal bread-pan filled with three pounds of stump-remover creates a bluing tank large enough for many small projects including handgun frames, the actions of many rifles (less barrels of course), and all sorts of small firearms component parts that benefit from bluing. Too, the three pounds of potassium nitrate in the bread pan is just about the right quantity of material when it expands and bubbles up when being heated to a liquid. Add no liquid of any kind to the potassium nitrate! The crystals will melt down into a liquid with heat alone, DO NOT ADD ANYTHING ELSE!
A Coleman stove or propane burner is perfect for heating and maintaining the temperature for our homemade bluing tank, and the potassium nitrate needs to be heated until it turns into a liquid form, whereupon it becomes a rather translucent yellow when fully up to temperature. When first melting down the powdered stump-remover version of this compound, it will bubble and foam with a brown almost glass-like formation as the crystals melt down, and the trapped air from the powder escapes. This is entirely normal, and merely stirring as the potassium nitrate comes up to temperature, and pushing the hard, clotted clusters of material that form back down into the liquid until all is melted, and the foaming action ceases is all that is needed to prepare your bluing solution. Once all of the material is melted into a liquid state, and the surface has been crystal-free for about fifteen minutes, you’re ready to blue those small parts that have been prepared ahead of time. Be aware that all parts must be completely free of oil and grease, and above all FREE OF ALL MOISTURE! Keep all water sources away from the liquid potassium nitrate, as a steam explosion will take place similar to getting water in molten lead! However, if you keep the bluing area free of water in all forms, you’ll have no problems at all in the bluing process.
I have a fairly large tablespoon that I’ve drilled with holes to make it almost like a small sieve and use it to support small screws for bluing, lowering the screws in the spoon into the liquid potassium nitrate for bluing. All other small parts are suspended on fine wire for easy retrieval from the hot bluing solution. Simply dunk the degreased parts into the molted bluing salts for fifteen minutes or more to get a nice deep, rich blue color, the longer the part remains in the bluing salts the deeper and richer the color (at least to a point). Upon removal quench the newly blued parts into a suitably large container filled with common motor oil. This oil quench does a couple of things, first it stops the bluing process and kills the bluing salts, second, while the pores of the metal are open and expanded from the heat of the bluing solution, the oil penetrates into the pores and creates a deep, protective layer on the newly blued steel that will last for many, many years.
Most people are absolutely astounded at how easy a simpler niter-blue hot bluing process can be, and more importantly the professional quality that the home hobbyist can achieve with such little expense or effort. The before and after photos of the small component parts to this carbine project speak for themselves.
After bluing all necessary gun parts, simply turn off the heat source under your bluing pan, and allow the potassium nitrate to cool of its own accord, and it will congeal and harden into a solid white mass. Cover the container with aluminum foil, and store away until the next time there is a project that needs blued parts, then it’s a simple matter to once again heat up the bread pan full of bluing salts, get them in a liquid state and get the job done. Saved in the manner described here, your bluing salts and improvised bluing tank will last years, and years and years! If kept from moisture, the pan shouldn’t rust out, and the bluing salts simply don’t wear out from occasional use. So, for six bucks worth of stump remover and a fifty-cent thrift-store bread pan a person has a lifetime of small parts bluing capability.