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Home Gun bluing -- cold bluing, selenium dioxide


Q. Hello! Could you help me please? I need a do-it-yourself kind of kit for gun finishing - (the complete process with the chemicals required) Parkerizing or black chromatizing. I want to start this as a hobby because we don't have any access to a gunsmith in my state.

Jonah L Pachuau
- Aizawl, Mizoram, India.

Parkerizing Solution at Brownells

(affil links)

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!

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

Q. I have some black powder handguns I'm bluing with store-bought gun blue [on eBay or Amazon affil link]. It didn't come out as good as I would like, and I noticed the main ingredient is "SELENIUM DIOXIDE". A friend of mine works for an aerospace firm and says he can get me some in powder form. I'm wondering if I can add this to what I bought at the store to juice it up a bit, or do I add it to water or what?

Dan Currie
- YORBA LINDA, California

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 affil link] (a tooth brush for smaller areas) and powdered pumice [adv: pumice on eBay or Amazon], then rinsing it and watching for a water break.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey


Birchwood-Casey Gun Bluing

(affil links)

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.

Bruce Johnston
- Pontiac, Michigan

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

How to make cold bluing solution

"Firearm Blueing and Browning"
by Angier

on AbeBooks

or Amazon

(affil links)

Q. I wish to know what type of acid is used to make cold blue liquid. I understand it can be D-I-Y by dissolving nails in a acid solution over a period of time. The resulting solution can then be used in place of commercial products. I suspect either citric or nitric acid is used.

Dave Hunter
- Cairns QLD, Australia

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.

Dan Brewer
chemical process supplier - Gurnee, Illinois

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.

Multiple threads were merged: please forgive repetition, chronology errors, or disrespect towards other postings [they weren't on the same page] :-)

Selenium dioxide vs. other cold blacks

Q. Looking to restore the black oxide finish on some specialty German made metric fasteners for a vintage motorcycle project. Although I'd prefer to outsource such work, all the local jobshops aren't interested in running a small batch or used parts for that matter. However, I have found 2 commercially available hobbyist kits that may work. One is a cold bluing kit for firearms, which contains Selenium Dioxide. The other is a cold black oxide coating kit from a automotive restoration supply company, but they will not mention the active chemical.

The questions I have, is cold bluing the same process as cold black oxide coating? If not, will bluing provide the equivalent rust protection as a black oxide finish? Will either of these processes cause any changes in the strength of the fasteners such as Hydrogen embrittlement? Also how safe is it to work with Selenium Dioxide and are there any disposal issues?

Mark [last name deleted for privacy by Editor]
- San Diego, California, USA

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.

John Smith
- Ann Arbor, Michigan, USA

! 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.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - 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 affil link] 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 affil links] 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 affil link]) 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 [adv: item 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.

Jim Howell
- Bacliff, Texas

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.

Todd Moase
- Kensington, P.E.I., Canada

Van's Gun Blue

(affil links)

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 affil link] 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 affil link] 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.

Christian Tisch
- Peoria, Arizona
April 11, 2008

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 :-(

Q. I'm trying to find out what to use as a black oxide (cold version) for a katana blade I have and I would also like to know where to buy it and how much it would cost.

Your help is greatly needed and thank you

Danie Thomas
- Oshawa, Ontario, Canada

Brownells Oxpho-Blue

(affil links)

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 link]) 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 affil link] or other cold blacks at most gun stores, or on-line from Brownells [affil link]. Best of luck.


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

Cold Blackening problem

Cold blacking with selenium dioxide+nitric acid + C opper sulphate is giving black but very loose coating, which can be easily wiped off with finger. Can you suggest me any solution?

Samir Joshi
PCP Chemicals - Thane, Maharashtra, India

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.

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

Browning vs. bluing

Plum Brown Barrel Finish

(affil links)

A. Older muzzle loaders are browned, not blued. A product called 'plum brown' can be bought on line or at your gun dealer. I did a couple of my friends' kit guns and they turned out great. To prepare the metal, I used #0000 steel wool [on eBay or Amazon affil link], then used the steel wool with liquid soap, dry and de-grease to get rid of any oil -- I use alcohol. You put the parts in the oven so that when you apply the plumb brown it sizzles, do this to the whole piece until it won't sizzle anymore. Wash with your steel wool and soap. Dry -- I use a hair dryer [on eBay or Amazon affil link] and then oil.

John t [last name deleted for privacy by Editor]
- salinas, California
August 14, 2008

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.

Bill Stevens
- Tucson, Arizona U.S.A.
December 1, 2010

!! I recently came across this line of products called Hoppe's.
It has gun cleaning solvents. They have a product called Gun Blue and I used it to get blue bluing and it worked. I was using this old French pistol and it came out excellent.


Paras s [last name deleted for privacy by Editor]
- Mishawaka, Indiana
June 19, 2009

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.

thumbs up sign 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.

Jacques Bolduc
March 1, 2012
- Matane, Quebec, Canada

Blue/black a large steel staircase and shelf units

Q. We are an architectural studio in Florence, Italy and are installing a large steel staircase, shelf units and railing system and want to end it with a blue/black finish. We have not found any 'finishers' here. We have been told to use selenium dioxide. Is this info correct, is it a liquid?

Any info would be appreciated.

Bruce Fernie
Designer - Florence, Italy
April 8, 2009

Hi, Bruce. Selenium compounds are usually associated with "cold blackening", so you might search for that term for more info, or buy a small bottle of "cold gun bluing solution" from a gun shop to get a feel for it.

I don't want to be critical of someone else's recommendation, especially when I haven't heard it firsthand and have listened to none of their reasoning, but I don't like that choice at all :-(

It will be "smutty", it will not be at all corrosion resistant unless kept oiled or waxed, and it will not be all durable. If you cannot locate a finishing shop for at least a hot black oxide (not that much better), I think you would be better off sandblasting, followed by application of a rust converter [on eBay or Amazon affil link] phosphate, followed by a nice blue-black paint. Good luck.


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

Mooney is quite right about acid blues. They are especially bad on things that you touch with your skin. The acid in your skin will strip off the blue and it will turn your hands and clothes black. Acid blues are at best meant for touching up small scratches. Hot caustic blue works wonderfully but you will never find anyone with a tank the size to handle what you are doing.
There are lots of other coating methods available. Plastic epoxy paints work well. What jumps to mind is powder coating. I'm by no means an expert on the subject although I understand the principal and I have seen it done. What I do know is that a lot of the kids up here are getting their motocross bikes and custom car and truck frames powder coated. They seem to be able to get it in every color of the rainbow and they claim it stands up better than paint. The cost seems about the same as a good paint job and if you can coat a monster truck frame with it I'm sure they could coat a little old stair case. I'm sure there is someone on these forums that could give you a good heads up on the stuff. ;o) Rod

rod henrickson
Rod Henrickson
gunsmith - Edmonton, Alberta, Canada

Old Bower /Barf finish is something ideal for your object.
Try Hammerite Rust Cap [affil link] paints as a more realistic option. Hope it helps and good luck!

Goran Budija
- Cerovski vrh Croatia

Does cold bluing react with silver?

Q. I have a steel part with some silver on it. I want to know if cold bluing the will react or change the silver and if so can it easily be buffed off. Thanks!

Tom Shandley
Hobbyist - Bellvue, Colorado
May 30, 2014

RFQ: What if I need to buy gallons of the stuff to do a non-firearms project. It's really just to temporarily protect the steel from surface rust...and yes, bluing is the best route for this particular application:
1. no need to remove
2. is not a coating
3. is not oily

Nu-Blu offers their bluing in quarts...but I'm thinking 5 gallon pail.
What do you recommend ... quality of finish / aesthetics is not an issue.
Does someone out there make an industrial bluing compound?


David Ford
Transportation - Victoria, BC Canada
December 6, 2018

Ed. note: Sorry, this RFQ is outdated so private contact is no longer available, but public technical replies are still welcome! No public brand/source suggestions please ( huh? why?)

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 supporting advertiser] is a major supplier of cold, warm, and hot blackening processes.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
December 2018


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