DIY Hot Bluing for Dummies (in progress) with pics

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INTRO
Decided to share some of my experience doing multiple bluing jobs on my own firearms.
It seems that there is no one thread here explaining process in detail start to finish. At leas I wasn't able to find on when I needed it.
While info on the Internet is available it's mostly sparse, incomplete or lacks details. Below is what I've learned and discovered over the course of two years throughpersonal experience and available publications.
And I'm ready to share those valuable tips that only come to you through trial and error experience with my fellows hobbyists.

Introduction to chemical metal refinishing
Phosphating (a.k.a. parkerizing) and bluing are both chemical passivation proccesses aimed at protecting steel against corrosion/oxidation and improving it's visual and (in certain cases) mechanical properties. Phosphating (or parkerizing) is relatively new technology, while bluing has been around for some time in one form or another.

Bluing - Black Iron Oxide
Iron oxide black (a.k.a. gun blue, bluing or 'blueing') is a conversion coating proccess. Meanning - iron in the surface layer of steel is converted to black iron oxide, also know as magnetite. Since magnetite occupies same volume as metallic iron there are no changes in part's dimmension. This is also why there is no destructive 'flaking/scaling' effect as with red iron oxide known as common red/orange rust. Bluing is accomplished by oxidation (or controlled rusting) by meanse of caustic bluing solution. No additional metall is added in this proccess, just converted what's already there into a diferent chemical form. In the sence it's same proccess that protects aluminum from oxidation - thin oxide film formed on the surface of the metal. With aliminium it happens on contact with air and in case of steel takes some caustics.

Parkerizing - Zinc or Manganese Phoshate
Phosphating (a.k.a. Parkerizing), on other hand, is a deposition coating proccess. Meanning - additional material is deposited via chemical reaction onto surface of the part, therefore somewhat increasing dimmensions of the part itself. Phosphating is done by emmersing part into solution of phosphoric acid, zinc and/or manganese with addition of some nitrates, chlorates, copper. When steel goes in contact with the solution chemical reaction takes place on the surface of the part and at this time manganese and/or zinc released out of the solution and deposited onto the surface of the steel. Some might notice that this proccess is simmilar to chrome/nickel plating, although acomplished without help of electric current.
 
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Health Hazards, Precautions, Legal Disclaimer and Liability Waiver

Legal Disclaimer and Liability Waiver
Following article is description of my experience and NOT AN INSTRUCTION MANUAL or DIRECTION TO ACTION. Information provided for entertainment purposes only. By continuing further you agree not to hold Author liable for any damages to property or personal injuries resulted from use of information and/or content of this site. If you choose to follow in author's footsteps, do it at your own risk or don't do it at all! If you disagree with stated above then you have to leave site immediately without continuing any further


Safety Precautions
!Breathing protection warning against inhalation of harmful substances and vapors!
!Both bluing salts and Park acids are corrosive and irritants even when diluted!
!Skin and eye protection is also strongly suggested!
!Warning for handling boiling liquids and heated metal parts!

Special note about SILICOSIS.
It's incurable medical condition associated with inhalation of dust containing silica, like the one generated during use of glass beads or sand for blasting.
 
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Equipment and setup

Shopping list of consumables
1. 6-8 gal of distilled water or clean rain water (not run-off)
2. 8 lb of pure tech or food grade sodium nitrate (a.k.a fertilizer or saltpeter)
3. 10 lb of pute tech or food grade sodium hydroxide (a.k.a. lye or caustic soda)
4. 1 gal jug of acetone
5. regular 'black iron' or better stainless wire
6. WD-40 or other post treatment of your choice
7. nitrile gloves. PVC will be OK but fall apart from acetone

Basic (minimum) equipment list
1. large 15qt glass enamel pot if no stainless available
2. stainless ladle for stirring and transferring bluing solution
3. 300F digital thermometer. analog will work too though
4. stainless mesh basket a.k.a kitchen sieve/strainer
5. heating implement: gas/propane burner or electric hot plate(s)
6. plastic pale with tight lid to store solution in-between bluings
7. plastic funnel
8. wallpaper tray for lon guns or clean supermarket meet trays for pistol only (hard plastic not styrofoam type)
9. quality OSHA approved respirator (recommended)
10. protective gloves and apron (optional)
11. eye/face protection of your choice

Advance work additional equipment list
1. bluing tank(s) - at least two, three better.
2. compressor with desiccant unit
3. blasting chamber and glass bead media
4. acetone storage vessel
5.
 
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Making your own bluing solution (needed chemicals)

There is more than one way to obtain chemicals for bluing. In some cases it is more cost-effective to purchase it from places like Brownels or MiwayUSA and in others to make it yourself, do your own math. It also depends on how much money and/or time you are willing to invest into the process. But since it's DIY, making your own bluing salts will be DIY as well.

Making bluing solution is easy. Make sure that you mix it in well ventilated area or oudoors.

1. pour 3 gal of distilled water in your pot
2. wear breathing/eye protection, maybe even apron, gloves
3. slowly add sodium hydroxide
4. then sodium nitrate
stay away from fumes while doing it.
5. place on the hotplate or gas burner and start heating it, stirring occasionally. It will take a while, so go relax in-between, but keep an eye on it making sure no kids or pets get their body parts in it.
6. when it comes to a boil and all ingredients went into solution - your bluing salts are ready to be used

At this point one might start submerging prepped parts in it and get good results. In my experience, however, I found that this formulation will make over-saturated bluing solution which will leave heavy layer of salts on the blued parts. While not detrimental to the bluing process itself, it will be hard to get rid of it during rinse phase, especially from captive areas.

I found that if I let solution cool down completely, excess salts fall-out into the sediment. I can then scoop out liquid phase into separate container and use it for bluing in it's unsaturated form and still produce very nice results. Those who used saiga-ak retainers had seen it.
 
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Surface preparation

I can not stress enough how important is proper surface preparation. Taking shortcuts is a sure way to suffer consequences. Just as in old Russian folk saying: "Wise one does it ones, lazy one does it twice".

Removing old finish
There are many ways to strip old finish from a firearm. Depending on what the finish is multiple approaches can be chosen, although abrasive blasting is universal approach that works great in most cases. Alternatives can be as follows:
Chemical paint stripper
I would not recommend this approach if you have access to an abrasive blaster or if you need to prep multiple long guns. Although it could be OK for 1-2 pistols, if you don't mind spending few hours doing it. It is very labor intensive. Chemical stripper is applied by a brush in thin layer. Then you let it sit from several hours to several days, depending on your particular type of paint and how effectively stripper able to brake it down (multiple applications might be needed). Following step is lots of brushing with soft steel brush, coarse nylon brush and steel wool until surface is clean as a whistle. this method works best on large flat surfaces i.e. pistol magazines. Rifle mags on other hand usually have stamped corrugations for rigidity and might be difficult in that respect. Paint stripper usually has no effect on bluing. Not all paint strippers are harmless. There might be very aggressive ones that CAN damage your furniture, plastic parts or even steel. So unless it states that it's safe for metals and other materials it might come in contact during refinishing, stay away from it.
Various bluing removers
I can not elaborate on any commercial kinds out there, because I have never used it. I did however used plain white vinegar and it worked relatively OK but still required additional surface prep.
Abrasive blasting notes - universal approach
It's all about the grit size. The finer the grit the better sheen will be achieved.
Plain glass bead gives nice satin finish that still looks hi-polish, but without strong mirror-like effect. Glass bead also removes the least amount of metal from parts compare to more aggressive medias like garnet or alumina. Crushed nut shell is largely ineffective for stripping anything beyond dirt. I personally switched to glass bead all together. It's cheap and easy to find compare to fine grits of alumina. Only downside is harmful silica dust, which can be avoided by using good respirator that capable of capturing very small airborne particles. I suggest ones that capture over 95% of particles.

Degreasing
Tiny droplet of trapped grease can ruin hours worth of prep and bluing. Remember that when you decide to go easy way instead of right way.
Usual culprits are pressed-on parts, permanently threaded joints, pins, spot welded or riveted joints.
I have used several different ways to degrease and clean my firearms for prep stage.
Dishwasher
However laughable it might sound, it is nevertheless good way to clean old crud and cosmoline stuck in the cracks and crannies. I used regular powder dish detergent and extra hot water. Sometimes it takes more than one time to really get 'old crusties' off. Some dishwashers have steam/power jets or 'Pots-n-Pans mode' that can be beneficial if your firearm has 'really bad case of dirty'. NOTE OF WARNING though, high value firearms should not be treated this way, although use your own discretion. Another thing to note that this exerciser will cause some light dust-like rust appear on the surface of the metal. Therefore this step is not advised as final degreasing procedure, but only as intermediate and if rifle will be subject to subsequent abrasive blasting immediately after. Needless to say you would need to remove wood furniture prior to subjecting you rifle to dishwasher treatment. Un-chromed barrels should be plugged too.
LCW NST cleaner/degreaser
I've used this one and it does a good job but it requires separate holding vessel, extra heating implement, extra rinse cycles and good ventilation.
It will also rust unfinished/bare metal, requiring additional abrasive blasting after it's done. It could be used cold too, but if you want to soak your really old cruddy gun in it, heating to 120F helps very much. Almost same results can be achieved by dishwasher for free and less equipment and headache.
Acetone
is an excellent degreaser. It's expensive but well worth it. It can be reused many times but should be stored in airtight container and handled in well ventilated area, SOB is so volatile that will evaporate withing minutes if left to it's own devices. I use this baby here to store my acetone and to soak barreled actions and parts prior to paint or bluing/phosphating. Watch out though. Acetone is not something you should breeze even a little because you might find yourself on the floor face down rather unexpectedly. On positive side it prevents formation of rust, dries instantly, doesn't affect metal in any way, therefore un-chromed barrels need not to be plugged.
Purple Power and Simple Green
I have not used these but people claim it works very well and environmental friendly. It also can be disposed properly much easier than things like lye.
Sodium Hydroxide bath
This chemical is a potent degreaser and used in soap and detergent making among other things. It can be used effectively to degrease AND preheat your parts prior to submerging them into bluing solution (I will speak of the pre-heating importance further down). To make degreasing solution mix by weight ratio 15-20% of NaOH to water. but be careful when doing it. To degrease/preheat parts place them in heated nearly boiling solution for 10-15 minutes. Then transfer directly into heated bluing tank
WARNING! Sodium Hydroxide is corrosive and CAN do serious harm if handled unprotected. Observe precautions and use safety equipment from above section. ALWAYS put Sodium Hydroxide in the water when mixing NOT other way around. Do it slowly. Watch out for splashes as it will burn you chemically and thermally at the same time. Stay SAFE!

Heat squeezing
This is the funny one too. When you work on parts that joined by some means together, there will be always oil trapped in those areas that can not be readily reached by acetone diping. Solution is alternating dipping with dry heating. When you heat metal it tends to expand and squeeze out grease from captive areas. Dip it in degreaser and heat again. Repeat this exercise 3-4 times or until no grease comes out anymore.
 
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Bluing

Bluing itself is simply suspending prepped part into solution while it's temperature maintained around 260-280F.
20-25 minutes in generally sufficient to obtain nice reach black color.
Watch out for splashes of hot salts as they tend to spew out of the pot/tank when parts are being submerged and captive air escapes.
Small parts should be placed in the basket to prevent lose. Large parts suspended by wires. Parts shouldn't touch or sit on the bottom of the tank. This might cause some areas not to blue correctly. Parts also have to be submerged completely because areas that stick out obviously will not blue.

Special note about bluing effect on bores and rifling.
Chromed bores will not be affected same as stainless.
Regular steel will take on blue and bores will look dark.
Some people advise to plug them to prevent this, others say it's unnecessary, since first 2-3 rounds shot through that bore will strip bluing clean and you'll have a shiny bore again. I personally lean towards second opinion just for the simplicity of it and the fact that most of the guns I blued either had dark bores already or were chromed.

Unlike phosphating where acids are used, bluing does not create chemical etching action and therefore not considered detrimental to steel.
 
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It's worth noting that there are several methods for bluing. Russian comrades differentiate "chemical paint" which can be both cold and hot bluing processes. There is also "raven...ing" or "воронение" which involves dry carbonizing bath, per Peasants and Workers Army manual for refurbishing of glorious Mosin rifle in defense of even more glorious motherland (1935)

Awesome thread, I hope we can stash some really good info here and make it a sticky.
 
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