Hot Blue

[Linstrum]

Our local library had their copy of Dunlap's book stolen just recently.

I need Dunlap's recipe for hot bluing and blacking, it is a good one and is simple. It uses Grant's stump remover and Drano "kitchen crystals" as the two ingredients for one version, the other uses ammonium fertilizer and Drano. The key ingredients are actually potassium nitrate and soda lye.

I made up some solution from memory and I'll be darned if I can get it to work! Usually to test it you drop in some nails and let it simmer for a fifteen minutes and you have the blackest, shiniest nails you ever did see. It is also a hard scratch-resistant bluing-blacking treatment, it withstands hard use just great. The down side is that it is not blue - it is as black as black can be. But it is EASY, - - - IF the recipe is handy! I do have a hunch that the stuff Drano sells nowadays is not lye because of the problem with droogies using it to make crack or some such mind-altering substance, and that is why my bluing solution no longer works.


rl316

[danski26]

I have Roy's book in hand. On page 391 he lists "Bakers basic solution" for hot blueing;

sodium nitrate 1/4 oz
potassium nitrate 1/4 oz
bichloride of mercury 1/2 oz
potassium chlorate 1/2 oz
distilled water 10 oz
spirits of nitre 1/2 oz

Is this the one you need?

[Firebird]

I think Linstrum is referring to the formula on page 399 of my NRA published copy.

5 pounds lye
2 1/2 pounds ammonium nitrate
per gallon of water

working temperature 285-295 degrees, soak 15-40 minutes depending on the hardness of the steel.
Have lots of ventilation when adding the ammonium nitrate as considerable ammonia fumes result.

Dunlap attributes this formula to Don Lowery and says this produces an unbelievably durable finish that can take a wire brush test without damage.

[Linstrum]

Okay, thanks, guys. Got it.


I had no idea that there were several different versions of the book, some with the recipe I wanted and some without.

For twenty years I modified the easiest formula of the bunch to make a REALLY durable hot black solution. I was using the formula on page 398 modified as follows:


65% Lye (aka sodium hydroxide)
35% Potassium nitrate (aka saltpeter)

Don't use the Drano lye crystals with little chunks of aluminum in it, the aluminum will prevent the solution from working. Use eye protection since a little lye in the eye may cause severe damage, even blindness. Mix the dry ingredients and than add enough water to make into a damp paste before heating. When heated it will turn into soupy liquid. Simmer your steel parts in this until the black surface is formed; probably in about 20 - 40 minutes. Like it mentions in the book you can't take the blacking off with a wire brush - plenty hard stuff!


rl417

[Linstrum]

Hi, Wills and Wicky:

I think a good dark phosphate finish is pretty nice looking. Last month I managed to obtain all the ingredients for doing the phosphate finish - phosphoric acid, manganese dioxide powder, and steel wool. I did several experimental batches using a Pyrex coffee pot to simmer the stuff in and I managed to get a light gray finish. The greenish dark color I want I have not been able to get yet. Ricochet suggested using a bit of copper salts in it as well, some of the Garand rifles are a dark olive green color I really like and they used a copper additive in the Parkerizing solution. I'll keep working on it and when I get the Parkerizing process figurred out I'll post that procedure.

Barrels MUST be plugged when doing metal bluing, blacking, browning, or phosphate/Parkerizing since the solutions are corrosive to the finely finished inner surface of barrels and all the other finely finished working surfaces like sears and other parts of trigger assemblies.

I left off one important safety warning about lye, aka sodium hydroxide or potassium hydroxide, which is when making up solutions with lye to add the lye to water, not add water to the lye since a violent steam explosion will result. Fortunately when mixing up a hot blacking solution like the one I wanted the recipe for where it contains both saltpeter and lye, the saltpeter refrigerates when it dissolves into the water and cools the lye. But caution is still needed since the solution is quite corrosive to skin.

I found the phosphoric acid for Parkerizing at both Home Depot and Lowe's in their paint departments. It is called phosphoric etch. The manganses dioxide I got from a pottery glaze chemicals supply house, it is actually pretty common for making black and purple glazes on pottery. I don't recall the name of the particular pottery supply house right now, I need to look it up on my credit card statement.


rl418

[drinks]

Most auto parts stores and hardware stores have the phosphoric acid, brand names are Ospho and Rust Stop, here locally.
For cheap potassium nitrate, check the sites for making amateur fireworks for technical grade, non food grade, material.

[XRING363]

FYI, stump killer is a very good source of potassium nitrate, 99% pure, 4/5 dollars a pound at Lowes/Homedepot.......

[Catshooter]

Gentlemen,

IMPORTATNT SAFETY TIP; You do not plug the barrel when hot blueing/blacking. As the air you've trapped in the barrel heats up the match the 290 degree lye solution it will expand alot and the odds are excellent it will blow out a plug. That can propell lye solution into places you didn't plan for it to go!

That blueing solution is dangerous stuff. Please make sure you understand what you are doing before doing it.

One does want to plug the barrel when Parkerizing. The solution is corrosive and at a much lower temp. The blueing solution can/is corrosive, but it's much slower, takes days.

"Add water . . ." Such a simple statment. Adding water to a working blueing bath is a bit like adding water to the working lead pot. Neither the bath nor the water like it! That hot lye on skin doesn't quite burn like liquid lead but it ani't pleasant by any means. And in the eye? Oh no thank you. Please don't wear safety glasses, wear goggles at least.

Sounds overkill, but a construction hard hat with the type of safety face mask that attaches to it is good. Can help from getting the solution behind your ear or down the back of your collar. Of course the long sleeve cotton shirt you're wearing is buttoned all the way to the neck, right?

Sorry to be so long, but there are just a few tricks to this work. It's like cooking bacon naked; not a good plan.


Cat

[sundog]

Junior, +1. I've done a couple with flat black exhaust manifold spray paint. The high temp stuff. Not sorry I did. Very durable. Good looking.

[Molly]

Here's a write-up on Caustic Blue that I did years ago for a neighborhood kid that was interested.

Molly
"Gun Blueing"
(Caustic Black Iron Oxide)

Bath Formula

Ingredient Chemical Weight Weight
Materials Symbol Measure Ratio One Gallon
Water (softened) H20 4 Pounds 64 5.2 Pounds
Sodium Hydroxide NaOH 4 Pounds 64 5.2 Pounds
Sodium Nitrate NaNO3 1 Pound 16 1.3 Pounds
Sodium Nitrite NaNO2 1 Ounce 1 1.3 Ounces

Some Primary Hazards
(A partial listing)

These chemicals can be dangerous. NaOH ("Caustic") will rapidly attack flesh, clothing and many metals. Spills should be flushed quickly with vinegar to neutralize the caustic and minimize damage. Mix dry caustic into the water in 4 or 5 small steps to avoid boiling the solution, or use commercial 50% caustic solution. Wear caustic resistant gloves, aprons and eye protection at all times. Don’t use bore plugs, which will splatter hot caustic if they pop out. Dry NaNO2 and NaNO3 can be explosive, just like lawn fertilizer.

Bath Operation

The solution tanks must be un-galvanized iron, steel or stainless steel, with welded seams. Soldered or brazed seams will dissolve, ruining solution, tanks, and whatever gets leaked on. Adjust the bath to boil at 275 F (135 C) to 302 F (150 C) by adding water slowly through a large fine steel mesh to catch spattering caustic. Don’t go over 310 F (155 C), or the solution will be damaged. Turning the heat down won’t work, as the bath must boil gently. Handle parts with steel wire hooks or tongs. Degrease in a hot detergent or caustic solution and rinse well. Then put them in the hot bath right away. Hang them away from the sides or bottom of the tank, but small parts can be placed in a steel wire basket. Let them boil for ~ 10 minutes, then remove and rinse in clean cold running water. Check color after scrubbing with clean, degreased “0000" steel wool. Return to the bath until the color is good. Rinse thoroughly, dry, oil and reassemble.

Trouble Shooting

Polish your metal well. Blueing won’t cover poor polishing. Poorly polished white steel becomes poorly polished black steel. Protect polished parts from rust with light oil until ready to degrease and blue them. Anything a magnet won't pull on (like wood, glass, aluminum, plastic or stainless steel) won’t blue, so don't put it in the bath. It could dissolve and ruin both the part and the bath. If a used bath is heated but won’t work, try adding a little more caustic or nitrate.

No color, or red or purple tones can be due to low temperature, copper contamination, low NaNO3, high carbon alloys or too little time in the bath. Green or pale blue colors can be caused by low temperature or not enough boiling action in the bath. Splotchy or un-colored spots can be caused by poor cleaning or oil contamination. Sometimes this can be fixed while blueing by scrubbing with degreased “0000" steel wool. A powdery black that scrubs off is caused by a worn out bath. No color can be caused by a worn-out or overheated bath, wrong amounts of chemicals or (in old baths) by caustic being used up by CO2 in the air.

[Molly]

BTW fellows,
I've noted ammonium nitrate recommended in some of the above formulas. Believe me, you'd better have an outdoors operation if you try it. I speak from experience! You'll be a lot beter off to substitute sodium nitrate. Still works, no ammonia odor.

[BeeMan]

I tried the potassium nitrate and sodium hydroxide (stump remover and lye) mixture a few years ago on a couple home made M dies and it worked great. I had read to use ice to add the water and it seemed to work fine with minimal spattering.

BeeMan

[Molly]

I tried the potassium nitrate and sodium hydroxide (stump remover and lye) mixture a few years ago on a couple home made M dies and it worked great. I had read to use ice to add the water and it seemed to work fine with minimal spattering. BeeMan

Hey Beeman,

I'm constantly amazed at how much there is on this board. I'd never heard or thought of using ice to add water to my bluing solution. I like it!

You might try the way I was taught: Take a 2 or 3 inch steel pipe - black iron is cheap & works fine - and make a hook to hold it - vertically - about an inch off the bottom of your tank. Get some fine _steel_ mesh from the hardware, and fold it into a funnel. Set the funnel in the top of the pipe. Fold the excess mesh over the outside, and use a hose clamp to lock it down. Now you can pour water into the funnel, and the steel mesh will keep the spatter from going all over you and everything in the shop. It's a little bother to set up, but it works great, and lasts forever. And if it should get gunked up, all you have to do is lift it out and hose it off.

[dubber123]

I just helped blue 20+ guns a few weeks ago, and the cautions on adding water and bore plugs should be heeded.

Just dumping water into 280+ degree solution can get really interesting, and one of the muzzleloader barrels we did had a plug in the bore to give an attachment point for the hanging wire.

A very few seconds after that one went in the tank, a 2 foot geyser erupted. No harm done, but taught me a lesson. That hot air needs a clear path out.

[HDS]

Okay, thanks, guys. Got it.


I had no idea that there were several different versions of the book, some with the recipe I wanted and some without.

For twenty years I modified the easiest formula of the bunch to make a REALLY durable hot black solution. I was using the formula on page 398 modified as follows:


65% Lye (aka sodium hydroxide)
35% Potassium nitrate (aka saltpeter)

Don't use the Drano lye crystals with little chunks of aluminum in it, the aluminum will prevent the solution from working. Use eye protection since a little lye in the eye may cause severe damage, even blindness. Mix the dry ingredients and than add enough water to make into a damp paste before heating. When heated it will turn into soupy liquid. Simmer your steel parts in this until the black surface is formed; probably in about 20 - 40 minutes. Like it mentions in the book you can't take the blacking off with a wire brush - plenty hard stuff!


rl417

Hi, sorry for bringing up this topic again but I was wondering what the specific recipe here is, how much water per lbs do you add to this recipe? I don't have the book you guys are talking about nor do I have any libraries that have it.

I like this one for it's simplicity and I got access to Potassium nitrate for cheap.

[Linstrum]

Hi, HDS, here are the particulars:

One gallon of water in 10 pounds of dry mixed salts

Operating temperature 290°F

Both sodium hydroxide (aka lye) and potassium nitrate are getting real hard to find and since you have access to potassium nitrate, grab up a bunch while you can. Lye type drain opener is often "denatured" with aluminum chunks about the size of #8 bird shot, so get the stuff without aluminum chunks mixed in with it since the aluminum both depletes the lye and kills the blacking solution so it won't work. Lye without aluminum chunks is what is used for making homemade soap, so get lye crystals suitable for making soap and you'll be okay. Check out soap making supplies online if you can't find Red Devil Lye at the supermarket or hardware store in the drain cleaner department. I got 50 pounds of lye crystals about three years ago from an oil and water well drilling supply company; lye is used for conditioning well drilling fluid and lye is sold there under its commercial name of CAUSTIC SODA. I paid $100 for 50 pounds, which is $2 a pound and is a good price if you can justify buying that much. Last time I bought lye at the supermarket it was $6 for 13 ounces. I make soap and clean my drains, so the 50 pounds will get used up. Sodium hydroxide = lye = caustic soda. Potassium hydroxide works equally well in place of sodium hydroxide, but it is very expensive and requires a bit more by weight to replace sodium hydroxide since it is a heavier molecule.

I use a modified version of Roy Dunlap's recipe consisting of 65 parts lye to 35 parts potassium nitrate. Dunlap's recipe calls for one gallon of water for ten pounds of dry mixed salts. Water weighs exactly 8-1/3 pounds per gallon (that is the definition of a gallon of water, 12 gallons of water weighs exactly 100 pounds). So by weight, the water is 45.45% of the total mix.
With the weight of water included in the mix, the new ratios are as follows:
35.45 parts lye
19.1 parts potassium nitrate
+45.45parts water
100.00 parts

The reason why I'm mentioning the re-calculated ratios to include water in the total is so you can make up small amounts of blacking solution, but of course the water has to be weighed unless working in the Metric System where one cc or milliliter of water weighs one gram. I have never made up a full ten pounds of salts with one gallon of water, For the most part I have only blacked little things like triggers, hammers, pins, screws, etc., and only a few ounces of salts is required for parts that you can hold in one hand and may be treated in a 10oz Campbell's soup can. When I did rifle barrels I put them down inside a skinny pipe so it only took a small amount of solution.

The amount of water in the solution rapidly boils off so more water has to be added VERY CAREFULLY while hot - it is imperative that you have full face coverage, gloves, long sleeve shirt, pants, and work shoes or boots so that no skin is exposed to spatters. Of great importance is monitoring the temperature of the solution since a temperature above about 350°F will destroy the strength of the steel by ruining its heat treat. Roy Dunlap lists 290°F as the working temperature. DO NOT USE A GLASS THERMOMETER, THE LYE RAPIDLY DISSOLVES GLASS! If mercury from a broken thermometer gets into the hot solution it will generate deadly poisonous mercury vapor. Use a thermocouple or remote infrared thermometer to check temperature instead.

Have fun!


rl740

[Linstrum]

By the way, welcome to the board!


rl741

[warf73]

Has anyone done this latley, what are you using as a vat to hold the soultion? I think a blacken finish would look great on my M44.
How clean does the metal need to be? I've done a dura coat on a shotgun with great results, would the cleaning procedure be the same?

[HDS]

I did my 1911 in a stainless steel cooking pot but you probably want something bigger. The cleanliness of the metal is very important I would say. I've seen some setups where they dip the parts in hot detergent solution, then clean hot water, then the bluing solution.

[louism]

If you look at the ingredients of a product called Drain Out it contains sodium hydroxide and sodium nitrate. It has just about the correct ratio of those chemicals. I have mixed those chemicals myself using products from the ag store and I have used the Drain Out with the same very good results. My most recent was a BP revolver kit my son and I did. It came out great using the Drain Out product. The big secret is in the polishing and cleaning.