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Old December 13, 2017, 03:13 PM   #1
dyl
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Supposed cold blue method that protects?

Hi folks, came across a Youtube video that supposedly shows a technique of cold bluing that provides rust protection. I wanted to run it by you guys for validity.

The quote here is "After years of experimenting with different cold blues, and trying to match the results of a hot blue, I came up with a method of achieving results similar to a hot blue. You know cold blue only chemically turns the metal black, it doesn't offer any protection whatsoever. Now this is something that will do that. "

Links is here: https://www.youtube.com/watch?v=X-CDOJF-TmY

To summarize, he preps a barrel, heats it up to about 200° with a propane torch, applies Mark Lee's Express browning solution, rinses and and cards with steel wool, and applies four or five cycles of Brownell's Oxpho blue solution rinsing and carding in between.

To my understanding, this still doesn't provide any true corrosion resistance to the steel. Perhaps the act of polishing the steel will remove some nooks and crannies that could start to rust first, but I don't think this creates a layer of oxides like hot bluing would. Perhaps the maker of the video feels that a deeper / richer/ darker cold bluing visually *hides* rust formation, and calls that protection.

Am I missing something here?
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Old December 13, 2017, 05:18 PM   #2
Oliver Sudden
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It seems to me he is rust bluing not cold bluing. Well done rust blue is considered by many to be the best finish any how.
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Old December 13, 2017, 06:25 PM   #3
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This isn't really rust bluing. The way rust bluing works is you start by inducing a very fine rust to form on the surface of the metal. This can be done with nitric acid fumes in a steam box or by applying one of several brands of solutions available to encourage room temperature humidity to do the job, including, IIRC, Mark Lee's bluing solution. You usually need at least 72% relative humidity to get the best job of rust formation. You then suspend the work in boiling water until it converts the red ferric oxide toward the black ferrous oxide. 15 minutes does as much as is going to happen, IME, and you want to use deionized RO water to eliminate mineral deposit water marks. Hard water refuses to cause the conversion, which apparently needs water in a relatively pure and more corrosive form (water is minimally corrosive at medium hard, which is around 7 grains/gallon dissolved mineral content). What you wind up with after the boil is a mix called ferric-ferrous oxide, which is blue. You then card the work (a fine wire brush on a buffer works well, but a lot of people use degreased steel wool; the iron traces it leaves behind seems to encourage the rusting process) to remove any of that oxide that is loose rather than bonded to the metal. That's usually most of it at first, and your first pass leaves you with a splotchy-looking steel surface peppered with dark places. You repeat and each time you repeat the exposed steel fills in more. After about six times through, you have a pretty good looking satin blue oxide finish.

In the video, I suspect a number of chemistry elements are getting sort of mixed up. First, Oxpho blue is one of the few cold blues that actually does offer some protection. I once took a half a dozen different cold blues and degreased and blued some music wire with them, rinsed them, and then let them sit around for a couple of months. All of them developed after-rust, some of which was really bad, except Oxpho-blue and Van's, both of which are phosphoric acid-based compounds. These make a black phosphate conversion coating (what manganese phosphate Parkerizing is) on the metal surface. It's just very thin compared with something Parkerized by submersion in heated phosphatizing solution. Also, it isn't so much blue as dark charcoal gray.

When you Parkerize, if you've never done it, you generally bead or abrasive blast the metal surface first to get a good bond from the process. I believe roughening and activating the surface is what the video author is accomplishing with the Mark Lee browning solution. The same result might be had in a number of other ways from a number of other solutions, including just etching the steel surface with some other acid, rinsing it off thoroughly, then applying the Oxpho-blue. I've never tried heating the work before applying Oxpho blue, so it may help. Hanging the piece in boiling pure water would get you to the right temperature quickly, but if you have a tank you can do that in, why not just rust blue in the first place? I think iron traces from his steel wool application is leaving traces of iron behind for the next application to react to, helping darken the work.

He didn't mention degreasing the steel wool. All steel wool is dipped in thin oil at the factory so it doesn't rust in the package. We used to soak it in tri-chlor to degrease it, but these days Naphtha or Xylene would be a better choice for your brain cells and works fine; you just need to let it sit longer. With the original rust bluing process, any trace of oil can interfere with it working, so steel wool needs to be clean for the most even results.

If I were looking to try something short of rust bluing (though, the video author isn't really saving much work over rust bluing; he probably just doesn't have a water tank to boil a barrel in), I would probably dilute the liquid form (he used the "cream" form) of Oxpho blue in pure water about 4:1 in a container I didn't use for food, and heat it and the barrel, then use a degreased fine wire brush to toothbrush it onto the steel. That approach slows the conversion and the brushing prevents dead spots. I just don't know what the heat will do to the color without trying it.
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Old December 13, 2017, 09:46 PM   #4
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Here is my best guess on the process:

The first part of the process is basically "rusetting" or "rust browning". It's similar to rust bluing, which many people are familiar with, but is actually an older process before the process of boiling to create black oxide was known or commonly adopted. It creates a uniform coat of Fe2O3 which will protect the surface somewhat but doesn't require the activation energy of Fe3O4 (bluing). This is done mostly on muzzle loaders and it is a valid finishing process.

This base will both protect the metal and may allow the oxpho-blue to do the conversion process required for the color.

I would be interested in trying this out and comparing it to just an application of Oxpho-Blue. Doubtful it compares to rust or belgian bluing, which can be done with just a little more equipment.
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Old December 14, 2017, 01:33 AM   #5
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There are several "express rust blue" formulas and processes, each with its own merits and drawbacks. Using a browning solution to rust a steel object before bluing it sounds like an awful way to do it. Brownells sells an "express rust blue" formula that works OK.

There are many old publications with formulas for rust bluing, most use toxic compounds and some are noxious and dangerous. The various cold blue processes, while useful for touch-up, are no substitute for real rust bluing or hot caustic bluing.

Every wanna-be gun tinkerer (some on this very forum) tries to use cold blues of various types with supposedly newly discovered processes to get a result they claim is "as good as" what they could get by just giving the gun to someone with hot blue tanks and letting them do their work (probably for less money than all the cold blues). I recommend doing it that way.
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Old December 14, 2017, 04:05 AM   #6
Bill DeShivs
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Browning and rust bluing solutions are about the same thing. Rust bluing requires boiling the part to turn the rust black, browning doesn't.

I agree that every neophyte has found the "secret" to cold bluing! I have too.
The real secret is- cold bluing sucks for refinishing guns!
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Old December 14, 2017, 06:47 AM   #7
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Just go with Express Bluing. You need a boiling tank to immerse it and steel wool to card it.
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Old December 14, 2017, 10:28 AM   #8
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That is rust bluing. I've used the Pilkington solution from Brownells thirty years ago when it was the only one they carried. Worked just fine, but seems to cost a small fortune, now. I expect either the Mark Lee Express or the Brownells Classic rust blue solutions work as well for less money.


Dakota.Pots,

I think anything that increases the total surface area of iron available will darken color. What I don't know is how that affects durability. In military phosphatizing, the old manuals call for the finished piece to be immersed in a very dilute hot chromic acid bath to reduce remaining free iron in the phosphate coating to prevent rust blooms from forming. Some modern surface prep and rust reducers have both phosphoric acid and potassium dichromate in them, which I presume is intended to accomplish the same thing in one pass. Also, most phosphatizing solutions need some iron in the solution, as provided by the atomized steel Brownells sells to make Parkerizing solutions more active, and perhaps the use of rust to create the high surface area performs that service for the Oxpho Blue solution, too.

Either way, I presume the magnetite form of oxide is less prone to exchanging oxygen with the iron in the substrate metal. I see no reason it can't provide the surface area and iron to the phosphoric acid, too. It would be interesting to compare a starting surface of boiled blue oxide to the brown one. I've seen antique guns, at one time browned, that had, through failure of their owners to keep them saturated with oil or grease, eventually developed a conventionally rusted surface. So I don't trust the ferric form's protection as far.
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Old December 16, 2017, 12:50 PM   #9
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Mark Lee Express Blue. A quicker method of classical rust bluing.

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Old December 16, 2017, 02:10 PM   #10
dyl
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Thanks folks, learned a lot of new things. I made the assumption that express browning offered no protection, and that all fast home-accessible processes offered no protection. This is great news. I don't have any refinishing projects that are a priority but it opens up some possibilities.
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Old December 16, 2017, 02:12 PM   #11
dyl
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And as a side note: who would have thought gunsmiths and enthusiasts were chemists? School would have been a lot more fun if they framed things to involve firearms...
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Old December 16, 2017, 02:44 PM   #12
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The gunsmith who refinished my smoked and steamed guns after the Incident including house fire used his own method for all-over reblue with Oxpho Blue on several of them. He said it is not the procedure Brownells gives for the job. Since they are "range guns" they have not been subjected to much wear or any adverse weather, so I can't say how durable it is. But the appearance is fine, equal or better than factory hot blue.

I think one of the Gunsmith's Kinks volumes has mention of using Oxpho Blue in a rust bluing procedure.

My FLG uses OB for touchup in sight cuts, etc. He always warms the part.

The Mark Lee Express resembles the old "hot water" or "fast" blue; substituting a torch for the boiling water heatup. You have to be careful reading the old witches' brew bluing formulae. "Hot blue" will mean the hot water method, not the "modern" dip in boiling nitrates.
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Old December 17, 2017, 06:59 AM   #13
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The Mark Lee procedure is to heat the metal to approx. 200 degrees F. , apply the Mark Lee product. Let it sit for a 5-10 minutes (the real difference from the "slow" rust method) then, dunk into hot water. I do have a problem with the Mark Lee product though. While it works very well on round surfaces, flat surfaces can have a somewhat splochy result. The flat surface will be black enough it's just not a nice even satin finish like this cylinder for example. While I am satisfied with the results, I really don't recommend this product anymore.



BTW that cylinder looked like this.



I have some experience with Oxpho Blue. The results can look very nice until you take the firearm outside into sunlight.

Last edited by arquebus357; December 17, 2017 at 07:06 AM.
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Old December 19, 2017, 01:24 PM   #14
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Thanks for that information. To me, waiting for the slow stuff to rust is less bother than trying to get something hot to the right temperature. I just always figure rust bluing takes six days that are mostly waiting and doing something else.
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Old January 8, 2018, 10:30 PM   #15
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Brownells' Oxpho-Blue does provide some rust protection. Not enough that you can leave a firearm outdoors in the rain for a week, but enough that the air in my basement doesn't turn a newly "blued" barrel red overnight (my basement isn't especially damp, but it's not heated).

However, I've found that the color produced by Oxpho-Blue isn't as deep a blue/black as a real hot blue job, or as deep as some of Brownells' other cold blue products (which, unfortunately, don't seem to provide any rust protection whatsoever).
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Old January 9, 2018, 10:55 AM   #16
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"real hot blue job" involves molten salts at like 600 deg F. No thanks

I will stick with rust bluing thank you very much.
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Old January 9, 2018, 11:06 AM   #17
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That is commonly called "nitre blue".
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