I just use solutions I buy off the internet. Brownells sells a couple different ones, all of which are good. One hint: buy a fresh jar if the old leftovers have some age to them, the stuff degrades with time. The last couple jobs I did I got the solutions from
www.rustblue.com. He mixes the stuff fresh when he fills the order, offers several different shades of blue (I like the "British gun" formula for duplicating the deep blue-black of early 99 barrels), and his prices are competitive with others.
You're on your own if you try to re-create the bright nitre blue finish on early M1899 receivers. That's something I never attempted. I simply rust blue and call it a day.
I boil small parts in a stainless steel sauce pan on a hot plate. For long stuff like shotgun double barrels, barreled rifled actions, etc. I don't boil them in a tank. I hit upon the idea of taking a piece of PVC pipe capped on one end, hang the long rusted object inside it, and pour in enough boiling water to cover it and let sit for 5-10 minutes. Presto, rust turns to black and the carding commences. Makes for a nice even blue and repeating the sequence only amounts to the same number of repeated sequences as immersing parts in a boiling tank.
I did build a crude sweat box out of scrap plywood tall enough to hang barrels and the like in, with a pan of distilled water sitting on a hot plate set at its lowest heat setting to create a damp warm atmosphere inside the box. It speeds up the rusting process and I feel helps with uniformity in color, as opposed to letting the parts rust in room air. I did one once by hanging the piece in a shower stall and running the hot water occasionally to keep the atmosphere inducive for rusting. Using the sweat box and the PVC pipe I can get a nice uniform blue in around four or five 2 hour cycles.
Most important thing is not which solution you use but how well you hand polish the parts beforehand and how strict you are about cleanliness. I don't go beyond 400x grit, but I take care to get all the fine sanding scratches running in the same direction on a barrel. 400x sanding scratches disappear under the bluing, but those that run counter to the rest do show up. After that, cleanliness is next to godliness. When degreasing I wear nitrile gloves to keep fingerprint oils off the steel, and a fresh pair of gloves are put on whenever I handle the parts for any reason during the whole rest of the process. Buy a box of those gloves, they're cheap. I do all degreasing with acetone and paper towels, no solvent washing between rust cycles. Use distilled water, not tap water. Trace minerals in tap or well water can play hell with the evenness of the finish, and a gallon of distilled water at the grocery store is only around $1.
Oils in the bluing environment are death to the process. I don't allow any aerosol lubricants in my shop- especially WD-40. All it takes is one errant airborne molecule of the stuff to create a spot on the finish that requires a complete startover.
Depending upon how tolerant your better half is about such things, rust bluing is something you can do in the kitchen. It's that easy and simple.
