The homemade salts are great for nearly anyone doing small jobs -- it is very quick and economical to heat only 1 gallon of salts, blue the parts, and shutdown in less than an hour start to finish.
I have not had bad or funky results with the homemade recipe. It works great even though I have not intentionally abused the process to find all potential pitfalls. If the item is clean and prepared properly the lye will finish "degrease" the part while the solution is heating up. I have even added parts that were degreased with Simple Green, quickly bead blasted, and then added to the salts and still gotten good results. I am not sure how many sessions I will get but it is nice to know the salts are inexpensive and there are no hazzardous shipping fees or large quantity minimums needed or wasted.
Disposal is a big issue for any of these salts and neutralizing the sodium hydroxide can be done with vinegar, water, and a ph test kit. I have heard of people putting the results down the drain, but I will not recommend disposal methods except to say consult the local waste disposal or sewer authorities and follow their rules. I consider disposal costs to be part of the job and I would not consider illegal disposal an option.
I may do more experiments with future batches. Steel is the only metal I let come in contact with the salts. I stick to steel or non-reactive materials for everything. I know some people say stainless steel would work fine, but I do not use it for the pot -- some say the pot can be stainless but others say it can affect the results. I find the enamel pots work great and are not that expensive.
The depth of the blackening color increases with more time in the bath and a repeat session can be done if there are touch-ups or to add more/depth of color. I found the exact same results from the process and it matches perfectly even after sanding, filing, bead blasting, etc. I scratched a part and just filed off the scratch, did a quick bead blast, and returned to the salts and reblued the exposed steel until it matched the rest of the part. The low temperature (255 to 275 degrees is helpful as I need only about 15 to 20 minutes to bring room temperature solution up to a full boil, then perhaps 20 minutes to 30 minutes exposure of the parts in the salts for a nice black result. If I cover the heated salts and turn off the heat it stays hot for quite a while so I can bring it back up to boil in 5 to 10 minutes for rework or additional sessions post inspection/cleanup on the first run.
I prefer to watch the pot while it is going, so I never leave it unattended while doing cleanup.
Attached are images of the ingredient packages that are very common. The ingredients and process are so simple nearly anyone can make it. If you can make instant coffee you can make this blueing recipe!
(5) 16 oz or 18 oz containers of Sodium Hydroxide (lye), Recommended Brand: Lewis Red Devil Lye Drain Opener (100% Lye). It must say 100% lye. Drain openers that explicitly say 100% lye are acceptable, howeer any drain opener that does not say 100% lye will not work! Lewis Red Devil Lye is a very common item so it should be available at a local home center, hardware or grocery store. The package is an 18oz container that costs about $3.19.
(Edited to add it has been brought to my attention that Red Devil Drain opener is no longer manufufactured, below is what someone kindly emailed me.
After a bit more research I did find that tech-grade sodium hydroxide is still available for sale at a variety of places with the most common being those that supply the homemade soap and candle making hobbies. I went ahead and ordered 10 lbs and with shipping it still only came out to $3.00 a pound which is comparable to the Red Devil lye if it had still been available. I purchased it here:
(1) 4 Pound Box/Bag of Sodium Nitrate (Nitrate of Soda), Recommended Brand(s): Bonide Nitrate of Soda Fertilizer, Dragon Nitrate of Soda Fertilizer, Hoffman Nitrate of Soda Fertilizer. This item is Sodium Nitrate and comes in 4lb bags or boxes. Garden centers and hardware stores carry this or can get it. It is listed as containing 16-0-0 or 15-0-0 Nitrate Nitrogen. If you prefer, you can order online by using a search engine such as google.com, froogle.com, shopping.yahoo.com, or bizrate.com to search for "Nitrate of Soda" and you will find merchants that sell it from $6.49 for 4lbs to $14.95 for 8lbs.
(2) 1 Gallon Containers of Distilled Water. Some people have no trouble with tap water, but I think it must be distilled so it does not contain minerals and it is available at every grocery store. I prefer to keep track of the water I add to the salts.
(1) 16 Quart Graniteware or Enamelware Stock Pot/Seafoood Steamer Pot (size works great for pistols). Do NOT buy aluminum. I have seen the enamel type of pots available online and in camping supply stores. I purchased from http://www.bedbathandbeyond.com for $19.95 plus shipping. Other containers of a similar size that are steel or black iron will also work.
(1) Propane burner and propane tank setup. I purchased a Turkey Fryer setup. You can select any setup and the aluminum or stainless pot will work great for post blueing cleaning/boiling to remove the salts. Most of these setups include a pot, thermometer, and the burner with regulator and cost from $30 to about $50 from home centers, hardware stores, or online.
(1) spool of ductile black iron/steel wire. Must be steel and appear either rusty or black. This is found in many home centers and hardware stores. Dip the wire into a degreaser to remove oil and diluted muriatic acid bath to prep for use.
(1) steel stir stick for mixing ingredients and stirring the bath to get the salts into solution when re-heating. Can be found in home centers and hardware stores. Select a piece 18" to 24" in length, 1/8" diameter to 3/16" diameter. You will know when the salts are ready when the stir stick starts to blue.
(1) 2 gallon plastic container with lid. Available at home centers in the paint department for storing the blueing salts between uses. Let the solution cool, then scrape out the pot and put the salts and solution into the pail.
SAFETY: Lye is poisonous, corrosive, and can cause severe burns if not handled carefully. The heated solution can burn you. Follow all safety warnings for the chemicals and the equipment and always mix in the recommended order out of doors in adequate ventilation. Never breathe the vapors, stand up-wind or at a safe distance when possible, and protect your eyes from the vapors or splashes. Rinse any solution from skin immediately.
MIXING: (All mixing should be done outside in good ventilation). Use a metal 16 Quart Steamer Stock Pot. Setup the heating source (propane turkey fryer burner).
1. Add 1 gallon of water into the pot.
2. Use a scale to measure five pounds of lye into a container. Slowly add 1 cup at a time to the room temperature water. Stir with a steel stir rod until each addition is dissolved into solution. If you add too much, it will clump on the bottom and be more difficult to dissolve. Continue to slowly add the lye -- the solution will heat up and there will be some fumes as the lye dissolves into solution. Avoid breathing fumes and go slowly with the mixing.
3. Place the pot of lye solution on the burner and start heating until the solution is warm.
4. Use a scale to measure 2 1/2 pounds of Nitrate of Soda Fertilizer into a container. Slowly add the fertilizer to the lye solution in the pot, stirring gently and allowing it to dissolve. As the temperature comes up closer to the boil, the fertilizer will go into solution.
Congratulations, you have just mixed your blueing salts!
If you are not planning to use the salts immediately, turnoff the burner and allow the solution to cool back to near room temperature. When the solution is not hot or too warn, you can pour the liquid into a plastic storage container and scrape the crystals to loosen and add them to the plastic storage container too. Rubber gloves and a plastic scraper help to completely clean out the crystals in the pot. Wash the residue from the pot with plenty of water to dilute and rinse it away.
Heat the solution until it reaches a minimum of 253 to 265 degress F and is vigorously boiling. Suspend the parts to blue using the steel wire to suspend them from a rod or piece of wood across the top of the pot. Let them remain in the boiling solution for 20 to 30 minutes depending on the steel and the depth of finish desired.
When you remove the items from the salts they are very hot. Place them into hot but not boiling water for about 10 minutes to flush the salts out of any threads or captive areas. Dry and inspect. If the item is not blackened to your satisfaction or there are areas where it is not even return it to the solution and let it go longer. When final color is reached and the part is washed of all salts, completely coat the part in oil (WD-40, Gun Oil, Marvel Mystery Oil). I have also submerged the parts in warmed oil overnight before hanging them up and letting the excess drip off. I have not seen adverse effects from wiping down the parts and admiring the beautiful black finish immediately.
Items can sometimes be covered with a soot -- this seems to be caused by excess heating, usually the result of letting the part sit on the bottom of the pot where the burner is elevating the temperatures. Other times, it just seems to happen for unexplained reasons. Underneath the soot, the finish is black, so let I always let it run and remain patient. After removing from the salts I place the part in a warm water bath and use a paper towel, rag, or a toothbrush to scrub off the soot. It will scrub or rub off and the finish underneath is usually very nice and black. Pipe cleaners will remove soot from small holes or screw threads. Once the surface looks clean, you can either return it to the salts for a few minutes or continue in a full hot water rinse, dry and oiling process.
Items that do not blue or appear plum colored usually need a little more time in the solution. Various steels blue differently, and contaminants on the surface can lend a hand in making the process go funky. Usually a good degreasing and return to the solution, use of a slightly higher temperature or a longer time will get them black.
If you have touch-ups or areas with defects that you want to fix you can return to the solution after corrective measures and a degreasing. I usually do touch-ups immediately while the salts are still running so I can assure the results come out exactly the same.
If you add lots of parts to the solution, it seems to take a little longer than when doing smaller bit of parts or touch-ups.
Ken Mays has more extensive experience with the original formula. Practical use is the same, but his recipe and mixing is different because ammonium nitrate fertilizer has several negatives: First, it gets attention from the FBI and you can end up "a person of interest". Second, when adding it to the lye, copious amounts of concentrated ammonia gas are produced and ammonia is very dangerous to living things! After his salts are mixed and working things are the same as what I am using, although he reports his solution boils at a higher temperature.