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Homemade Hot Blue Formula


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#1 Reverend Recoil

Reverend Recoil
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  • Interests:Registered Industrial and Mechanical Engineer, LSU graduate. Project engineer in the perto-chemical industry.<br /><br />Interests: gunsmithing, Bowie knives, traveling with my wife, photography, medium stakes Texas Hold'em poker, blues harmonica, and having fun and shooting with my three sons.

Posted 03 July 2005 - 11:12 PM

Homemade Hot Blue Formula
Courtesy of Blair Emory
(my comments in brackets - KM)
All "bluing" is really blacking. The blue shine is due to additional chemicals such as manganese that are added to the mix. They are usually less abrasion resistant than blacking and perforce are thinner to give the blue refraction. They are a lot fussier to do and the results vary more than straight blacking on different metal alloys and heat treatment in my experience. I generally use a lye, fertilizer mix that gives the hardest blacking I have ever seen and it so simple anyone can do it, plus the ingredients are available at the hardware store rather than paying UPS hazardous shipment fees.
1. The mix ratio is 5 lb lye (sodium hydroxide) to 2 1/2 lb ammonium nitrate (fertilizer), to 1 gallon water.
2. Grocery store lye and ammonium nitrate fertilizer (at least 30%). Make sure you are buying actual ammonium nitrate; many brands today are made from urea or some other source. Make sure to not use tap water. Buy distilled. [Note: I found Red Devil lye at Albertson's supermarket. I had to go to a feed & seed store to get the fertilizer. It may prove hard to find, but the country seed & feed stores can usually get it.]
3. Mix out doors as lots (and I mean LOTS) of ammonia gas evolves and will rot your lungs out if you sniff it. Wear goggles as this stuff foams and bubbles like mad. Very violent exothermic reaction. Mix in a iron pail (not galvanized). Once mixed and operating the bath, there is no off gassing, but the vapors are corrosive so don't do it in your gun room or machine shop. Use plenty of ventilation. [I added water first, then added 1lb of lye and alternated with fertilizer. Add slowly to avoid boilover. Also, use a full face shield and a respirator that will filter out ammonia. I bought both of these at Home Depot.] After mixing, the solution will be over 100 degrees due to the heat of the reaction.
4. Bath operates at 285 to 295 degree F. If you don't have a thermometer, heat until a sample part will just sizzle cold water. [I found a steel deep fry thermometer at Home Depot. Make sure the one you buy will reach the bottom of your pot. I bought an enameled 16 qt stock pot at Wal-Mart, and used a propane deep fryer kit.] Takes 15 to 45 min. depending on the steel and how dense a film you want. [I removed my gun after 20 minutes.]
5. After you are done, take parts out, rinse in clean water, dry and oil. You are ready to go. If you don't like the depth of color after it's dry, (but before you oil it) just put it back in the bath and cook it some more. [Some of my parts had a soapy, waxy coating when removed. The slide & frame were coated with a fine red rust that I had to rub off.]
6. Bath will do 10 to 15 jobs before you have to add about 1 lb lye to a 5 gal bath to make up for boil off. Add water as required to keep the concentrations correct, but this does not seem critical.
7. You MUST add enough water at bath cool down, to more than make up for boil off or it will solidify and you can't re-melt easy. If you add too much, I will just boil off next time. [This stuff takes several hours to cool back down. Once it gets hot, it really stays hot.]
8. Make sure the parts are clean. Any oil will ruin the bath and job. Boil parts in TSP, Oakite or such first. [I found some TSP at Home Depot. Be sure you have wiped away any water spots, or they will show up under the bluing.]
9. Store in glass or plastic jugs between use, if it crystalizes , it is shot.
10. You do not have to plug the bore as the magnitite film is harder than the steel and, if anything, should improve it. Possibly a little chemical milling too. I have made test coupons and put them in an open beaker of water for a month with no corrosion. Even light sanding will not break down the surface.


I would like to thank several people who helped me realize a hot blue formula that works and is fairly simple to put together from chemicals that are not impossible to find or hopelessly expensive.

If you are looking at the salts sold by Brownell's and other companies, you definitely are out of my league. If you need to blue large items and long guns, you probably want to think about the kits too.

I got loads of information from a website formula (Ken Mays) -- it recommended using ammonium nitrate and lye. Here's the link:

Homemade Hot Blue Formula

The advice and assistance provided from him made it possible for me to find a solution that worked without making me a person of interest or causing injuries. I would not be home bluing without his assistance and advice.

The difficulty with ammonium nitrate is that people consider it equivalent to asking for a stick of dynamite at the hardware store -- a. it is not going to happen and b. you will get more attention than you ever want. Places that stock it are advised to report strangers asking for it, especially in small quantities, and there is a good possibility you would be contacted by "friendly" authorities.

The original recipe was out of the question for me after making a few inquiries and learning about the consequences. The great news is that there are alternatives that work great. I have one that is tested and I now use it regularly with great results.

Instead of ammonium nitrate, I use sodium nitrate (Bonide Nitrate of Soda) available for a few dollars in online gardening websites. You can do an identical substitution using Sodium Nitrate instead of the ammonium nitrate -- it is close to perfect, but technically, you should add about 4 ounces more Sodium Nitrate. My first batch is an exact substitution and it works fine. I added the extra 4 ounces to the second batch and it made no differences.

Benefit to Sodium Nitrate: it does not give off the nasty ammonia gas clouds or get the attention of neighbors or the local HAZMAT team. The temperature it works successfully with starts about 260 to 265 degrees too.

I "cook" my formula in plain view of the neighbors and aside from when I mix ingredients and clean up it hardly generates any questions. Mostly they ask if what I am making is any good. I reply "its homemade" : )

Here's the brand of Sodium Nitrate that has been fairly easy to find online for ordering. If it is close to 15-0-0 then it will work great.



I used the exact equipment and setup from the original formula website. My turkey fryer runs about 265 degrees F and does a super job in about 25 minutes. I have used it to reblue many parts for reloaders, case feeders, and a couple of pistols and will never use cold-blue on a part or pistol again.

I'd really like to see what others do for hot blue setups and see if they will join on this discussion.

I have also read that potassium nitrate can be substituted for the ammonium nitrate. Potassium nitrate is available at Lowes as Green Light Stump Remover.

To keep the concentration of nitrate equal to the original formula (ammonium nitrate) you have to add 6.25% more sodium nitrate and 26.25% more potassium nitrate. I purchased some potassium nitrate (stump remover) and will post if it worked. Thanks for the great info

I tested my luck and bought another brand, Grant's Stump Remover. No indegredients on the label but a search for the msds revealed 98% potassium nitrate.


#2 sonic1

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Posted 28 August 2005 - 06:33 PM

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