Home Gun bluing -- cold bluing, selenium dioxide

A. The basic gun finishing process is black oxiding, Jonah. This consists of immersing the cleaned parts into a boiling (about 265 °F) mixture of strong oxidizing salts including sodium hydroxide and nitrites. There are also phosphatizing (parkerizing) processes for moving parts, and cold blackening processes that are safer but not as good. Our FAQ on black oxide and cold blackening is a start. Beyond that, you can search this site for many threads of conversation on the subject. Good luck!

A. Hi Dan. I seriously doubt that as an amateur, presumably with limited chemical knowledge, that you can improve on the formulation of commercially available gun blues. I think the most likely cause of your gun not coming out as well as you would like is that it wasn't truly clean. Dip it in tap water or spray it with a hose, and if you see any "water break", it's not clean enough.

In industry we use boiling hot, very strongly caustic, cleaner solutions with electrolytic and/or ultrasonic agitation. Hot electrocleaning is probably impractical for you, so I'd suggest scrubbing it with a scrub brush [on eBay or Amazon] (a tooth brush for smaller areas) and powdered pumice [on eBay or Amazon], then rinsing it and watching for a water break.

Luck & Regards,

Q. Dan,

I was curious to see how it went. I tried the same bluing from Birchwood-Casey and my job came out black. After contacting them directly, they stated that if I wanted to get the bluing BLUE, then send it to the manufacturer I got the barrel from, because their formula doesn't blue, it blacks. I have been searching for a "Blue" bluing since. I am in the process of restoring a 1935 8 mm Mauser and want to do the job myself.

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Bluing vs. blackening

A. Hi, Bruce. You are more limited in cold bluing than you would be in hot bluing--but hot bluing is quite dangerous and can be complicated. We have an FAQ comparing the two processes.

Something to realize about all blackening vs. bluing, however, is this: a matte surfaces always tend towards black for two reasons -- because rough surfaces bounce the light back & forth gradually absorbing some of it instead of mirroring it directly back; plus rougher surfaces have more surface area and will absorb more dye or colorant. A very highly polished surface will always look much brighter and more of a jewel-like blue with the same bluing/blackening chemistry. See if you can mirror polish a small object before bluing it and then tell us your result. Thanks, and good luck!

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. It sounds like you're being penny wise and pound foolish. Save yourself the headaches (and possible environmental catastrophe) and go to the local gun shop and get a kit to blue your guns. As an FYI, it's the oil over the blackening that makes the gun look blue, and the usual acid is hydrochloric with selenium.

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Ed. note: Dan & Ted are on the same wavelength here: whether it's due to a more polished surface before bluing, or whether oiling the surface after bluing helps smooth it, rough surfaces look blacker and smooth surfaces look bluer.

A. Soluble selenium compounds are hideously toxic. There are no disposal issues, but wear disposable polyethylene plastic gloves and then wash your hands very thoroughly with soap and hot running water after handling the stuff and taking off the gloves, whether you think you got any on your hands or not. Selenium dioxide based "cold blues" produce a finish that can be patchy and blotchy, and does not wear especially well.

Alternately, you could get the phone book and look for gunsmiths, who, I'm sure, will be only too happy to do the job, and they'll surely use the hot caustic blue process -- which wears a lot better than the selenium-based coloring and also tends to look better.

I considered going into the details of doing hot caustic bluing at home here, but the process is not without its dangers (the solution contains high concentrations of caustic strong alkali plus a strong oxidizing agent, and therefore it goes through flesh like a buzzsaw even when it's not at a full rolling boil), so I won't.

! Your warning on hot caustic bluing is well taken, John, and I personally think the temperature is an even bigger problem than the caustic. Water flashes to steam at 212°F whereas these tanks operate at 265-290 °F and more. One foolish man was having a soda while bluing, dropped the can into the tank, and it exploded -- showering him and causing his death. Other operators have learned that a rumbling sound can mean run for your life: a slug of water is being heated by the tank contents and may be about to blow. These tanks require proper mixing methods so water can be safely added to make good the rapid evaporation losses.

As to Mark's other questions: yes, "black oxide" and "gun blue" mean exactly the same thing, but hot methods are more reliable & robust than the cold methods. Bluing is unlikely to have much hydrogen embrittlement effect, but acid dipping before bluing (if done) will. Even the best hot bluing, let alone cold bluing, is not very corrosion resistant ... it's the gun oil that people keep on it that does the most to deter rust.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. I've been spending years using all the available products available for bluing guns and gun parts as a hobby. I believe I may have the answer to most problems (HEAT)
I've found lists of comments that this is the secret. It is true. This isn't something you do in a hurry or do without precautions. These chemicals are POISON and I've been careless and have been sick and arthritic curling fingers by not taking the proper safety measures (lesson learned).

Birchwood works best. Got to be clean. Preparation by removing rust and blue is not an option, it is amazing how it works. Then comes the trick, propane torch, not too hot but hot enough you'll burn the crap out of yourself if you touch the area (DUUH). When it's clean and hot you can see the color changes in the metal being very careful -- not too hot. Experiment on junk -- very important. Swab the bluing on -- one time , one direction, big or small area let set for 30-40 seconds -- take to sink and rinse it good. Don't wipe. Dry with Clean and dry paper towel lightly use small 00 steel wool [on eBay or Amazon] to blend only. Degrease, wipe off and do it all over starting with the torch, over and over. 10-20 times. After the first time you'll say "Jimbo knows his stuff". Very important to use vinyl or rubber rubber gloves [on eBay or Amazon] in all stages. The steel wool sticks into you and hard to pick it out of your skin. Last thing, use a moto tool ( [on eBay or Amazon]) with a small buffing wheel and polish like crazy. Don't use any abrasive and do it lightly in full strokes. Be careful because cold blue even with heat is shallow and you may have to get out the torch again. This works and remember it's dangerous (chemicals, torch = danger) Keep chemicals away from torch like remoil, WD-40 [on eBay or Amazon] and bluing solutions. The most caustic is the bluing and rust removal. The smell is of HCl = strong acid. Got to get that off everything and it works fast. Try it and let me know.

A. I am getting into hunting for my first this fall, and I was given an old Winchester 1200 pump. I love the gun but it was in rough shape, so I stripped the barrel and blued it myself. It took a lot of work and time, but I think it looks very good, no problems whatsoever and it has a nice blue when out in the sun.
I simply tore down the gun, sanded the barrel with 220 grit sandpaper, till it was nice and shiny. Then I rinsed it with water, and used a degreaser to remove any oil left. I put on rubber gloves to avoid oil from my fingers and I used Gunslick blue. Put a coat on (be careful it spreads and dries fast), let it dry, then I wash with hot water. It will then look like rust, simply take extra fine steel wool and polish, repeat 7 or 8 times, then let air dry and buff with steel wool and cover with oil, looks brand new.

A. Just a comment about Cold Bluing. I just refinished a 1938 Large Ring Mauser 8 mm with the step barrel. The original finish was completely gone although only a few minor pits. I sanded it with three grades of automotive wet dry paper. First 400, then 600, then 800 paper. I then degreased using brake cleaner, acetone [on eBay or Amazon] works as well as carb cleaner.

Using an old cotton t-shirt cut up to appropriate size I saturated it with Van's Gun Blue rubbing vigorously as the color got deeper and deeper the more I rubbed. I then wiped it dry with a dry old cotton towel. At this point I rubbed with #0000 steel wool [on eBay or Amazon] and got the deepest high polished barrel second only to real high grade factory finishes. It was positively better than I ever expected and total time was about two and one half hours. I just finished a Swede 6.5 carbine which I paid $250 and now can expect $600 easily. This Van's is all it's cracked up to be and more. Highly recommended.

Chris Tisch formerly of the Peoples Democratic Socialist Republic of New Jersey. Now safely residing in Arizona where God, Guns and Guts still rule.

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Ed. note: Casual digs beget casual digs :-)
Although your assessment of New Jersey may not be far off the mark, at least we're known for a wide range of things whereas Arizona's sole claim to fame seems to be the manufacture of shock torture devices :-(

A. Hi Danie. Remember that black oxide, especially cold black oxide, offers essentially no corrosion resistance except for the light oil or wax (wax [affil links]) that you keep on it. So if scratches bother you, this would be for display indoors only.

Cold black oxide processing solutions are based on selenium dioxide (they look like black rust, but they are not actually) and they're a bit "smutty".

Sending it to a gun shop for a hot black oxide would really be better, but if cold black oxide is still what you want, you can get Birchwood-Casey cold blacks [on eBay or Amazon] or other cold blacks at most gun stores, or on-line from Brownells [affil links]. Best of luck.

Regards,

A. Yes. Hot blackening :-)

Cold blacks are invariably somewhat smutty, but if it is coming right off, the application or formulation isn't right. The parts are alkaline cleaned and acid dipped before blackening? Have you had success before but something changed? Any clues at all about what those things are? I did know that selenium and nitrates are part of the formulation of cold blackening solutions, but I don't personally know the actual formulation because most shops in the USA use proprietaries. Sorry.

Actually I wanted to respond to a letter written by John T from Salinas, Ca. Normally I wouldn't respond to this type of submission but there is a serious medical concern here. It is alright to heat this product in an oven. One must also bake powder coat in an oven to get the final finish. However, Mr. Thomas failed to mention anything about NOT baking your chemicals in the oven you may very well be cooking tomorrow's turkey dinner in.
You must NEVER use chemicals in your old daily user; if you do YOU CAN DIE FROM IT.

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Ed. note: We'll be happy to acknowledge otherwise, but we think that, although Hoppe's offers cleaning and gunstock chemicals, they no longer offer bluing chemicals.

I just want to say thanks to Jim Howell and Ted Mooney for the tips that they gave.
I tried Jim's procedure for bluing and it's works very well. The steel has been heated at every layer of blue and it's nice and strong.
Thanks
Jacques

A. Hi David. This particular thread is about cold bluing at home but we have numerous threads about the industrial application of cold bluing as well as hot black oxide processing. When looking for industrial quantities, try googling with the term "black oxide" or "cold blackening" because that's what industrial users usually call the process rather than bluing.

See if you can find a local distributor of metal finishing processes. EPI / Electrochemical Products Inc. [a finishing.com supporting advertiser] is a major supplier of cold, warm, and hot blackening processes.

Regards,