The Bullshooter

Wednesday, March 22, 2006

Touch-Up Blueing at Home

What many people do not realize is that the blued finish on your rifle, pistol or shotgun is actually a form of controlled corrosion. Blueing itself is not a protective coating against rust, which is why guns need to be wiped over with gun oil after use. Even the acid in our finger marks can result in rust starting - sometimes within hours (it depends on just how acidic the individual... so keep your mother-in-law well away from your gun safe! Har har! Just kidding, Dear!).

The depth and quality of the blued finish can depend not only on the process used, but also the composition of the metal. Not all gun steel is created equal. The more ferrous the metal, the easier it will take on a deep blue finish (also the easier it will rust). Most rimfire barrels are made from a very low grade of steel, called black steel. This is not a bad thing, since it only has to deal with very low pressures and soft lead bullets. But black steel has a high carbon content, and blues beautifully.

With modern technology some factories have, for reasons best known to themselves, taken some unforgivable liberties in using high alloy content steels that result in ugly old age. The classic example if the Winchester Model 94 lever action. Somewhere in the 60s or 70s the receiver was cast in a new high-alloy metal. I'm sure the decision was economic. These rifles are mostly carried with a hand wrapped around the action, and even with moderate use the blued finish wears off. I'm afraid there is nothing I can do to help this type of rifle... even the methods I'll be giving you for optimizing cold blueing will result in nothing better than a sickly gray smudge.

If you have any form of firearm that is (or could one day be) worth money, don't fool with it. Give it to a professional gunsmith for a proper reblue, or simply leave it in its original finish - most often collectible firearms are best left that way.

If, on the other hand, you have granddad's old single shot, that has mountains of sentimental value, but will never be worth more than a few beans, and you want to tart it up a bit without spending buckets of cash (professional reblues are not cheap) - then you're in the right place.

This can also work for touching up parts that have lost their finish, but be aware that if you intend touching up only part of a larger component like a barrel or receiver, the new finish will likely not match the old.

There's really no fail-safe way of knowing exactly how the steel will react to the blue, but a good way of finding out if you're dealing with high ferrous content is to try a strong magnet against it. If it sticks like crazy, it will probably blue okay. If it shows limited interest in attaching itself, chances are it's high alloy content and the blue won't take very well.

You Will Need

Quantities of steel wool, OOO Grade (the finest), and maybe a couple of slightly coarser grades.
A bench polisher, with wire wheel (ideal but not absolutely necessary).
Safety goggles and protective rubber gloves.
A tube or bottle of touch-up blue. My favorite is G96 paste, as shown, but any reputable brand will do.
A bottle of gun oil.
Scraps of cloth that will NOT be useful for anything later.


Ideally the part(s) you are blueing should be taken back to bare metal. A bench mounted polishing wheel does this admirably. Not as good because it takes a lot of time and effort, is steel wool, which I always use wet with gun oil. Never, ever use sandpaper. Even the finest grade of wet and dry will leave scratch marks that will show through the blue.

When the part is polished, don't leave it for any amount of time "in the white" (bare metal), because even though you may not see it, rust takes a hold immediately.

Before applying the blue, you must first degrease it completely. Acetone works great, although there are some gun degreasers that would probably work okay.

Don't forget the gloves at this stage. You're dealing with some nasty chemicals here. And make sure you have good ventilation so you're not getting too much of a whiff of this stuff.

IF POSSIBLE leave the part where it will get warm. Heat helps the blue "take". Sitting it in the sun on a hot day for 30 minutes would be perfect.

Liberally apply the cold blue solution to a wad of OOO grade steel wool, and rub it into the metal. It should darken immediately. Do not be too concerned if the finish is not entirely even at this stage. Sit the part down and leave it for about 30 minutes, NO LONGER.

After 30 minutes, take a cloth, apply gun oil to it, and wipe the part over completely. Don't overdo this. When you have wiped all of the blue solution off, and the surface appears to have a thin film of oil, set it down and leave it.

24 hours later you MUST give it another heavy coat of gun oil. The first coat will 90% neutralize the chemical reaction of the metal to the blue. When you come back a day later, chances are the surface will be dry, and may be showing outward signs of corrosion, maybe a brownish powdery tinge. This second coat of oil should stop the blueing (or corrosion) completely.

Of course you should regularly check for any spot that may have missed being neutralized over the next few days.

Most of the cold blue instructions will tell you to wash the part in water immediately after application. This is their safe way of ensuring that chemically-induced corrosion stops there. Unfortunately it also limits the effectiveness of the blue. My technique grew from dissatisfaction with the patchy results I was getting from following their instructions. Your mileage may vary, so I'd recommend starting with minor parts to see if this technique gives you the results you expect.


  • At 3/4/06 6:00 PM, Blogger Z said…

    Nice technique. Similar to my approach, but I never thought about heating the part. Just reblued the front sight on my Toz using Brownells Dicropan, your procedure, and finished with Beeman MP5 oil. Looks great!

  • At 23/11/11 9:03 AM, Blogger Brett Barbaro said…

    Love your column. I figure you're the best qualified to answer this question:
    What happens if you just leave the bluing compound on? Will it pit? Will the reaction eventually stop? Will the bluing get any deeper/more protective? I've always wondered, but don't want to try it! :)
    Thanks for your reply, B

  • At 23/11/11 1:47 PM, Blogger Warren said…

    It will turn to rust, and pit quite quickly if left without oil. As mentioned in the article, blue is a form of controlled corrosion; let it go too far and it will damage the metal.


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