Announcement

Collapse
No announcement yet.

Anyone done hot caustic bluing?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Anyone done hot caustic bluing?

    Going to give it a try. Want to black oxide some small parts. Seen people do it on YouTube, but no recipies. I have a fume hood, and plenty of safety gear, so please no shoot your eye out comments. Best I can find is lye, water, and potassium or sodium nitrate. Just looking for advice and or tips from anyone who has done it.

  • #2
    This was what I used when I last did it (CAN'T POST A .PDF OF ADEQUATE SIZE, SO HERE'S THE TEXT):

    Code:
    The homemade salts are great for nearly anyone doing small jobs -- it is very quick and
    economical to heat only 1 gallon of salts, blue the parts, and shutdown in less than an
    hour start to finish.
    
    I have not had bad or funky results with the homemade recipe. It works great even
    though I have not intentionally abused the process to find all potential pitfalls. If the item
    is clean and prepared properly the lye will finish "degrease" the part while the solution
    is heating up. I have even added parts that were degreased with Simple Green, quickly
    bead blasted, and then added to the salts and still gotten good results. I am not sure how
    many sessions I will get but it is nice to know the salts are inexpensive and there are no
    hazzardous shipping fees or large quantity minimums needed or wasted.
    
    Disposal is a big issue for any of these salts and neutralizing the sodium hydroxide can
    be done with vinegar, water, and a ph test kit. I have heard of people putting the results
    down the drain, but I will not recommend disposal methods except to say consult the
    local waste disposal or sewer authorities and follow their rules. I consider disposal costs
    to be part of the job and I would not consider illegal disposal an option.
    
    I may do more experiments with future batches. Steel is the only metal I let come in
    contact with the salts. I stick to steel or non-reactive materials for everything. I know
    some people say stainless steel would work fine, but I do not use it for the pot -- some
    say the pot can be stainless but others say it can affect the results. I find the enamel pots
    work great and are not that expensive.
    
    The depth of the blackening color increases with more time in the bath and a repeat
    session can be done if there are touch-ups or to add more/depth of color. I found the exact
    same results from the process and it matches perfectly even after sanding, filing, bead
    blasting, etc. I scratched a part and just filed off the scratch, did a quick bead blast, and
    returned to the salts and reblued the exposed steel until it matched the rest of the part.
    The low temperature (255 to 275° F) is helpful as I need only about 15 to 20 minutes to
    bring room temperature solution up to a full boil, then perhaps 20 minutes to 30 minutes
    exposure of the parts in the salts for a nice black result. If I cover the heated salts and
    turn off the heat it stays hot for quite a while so I can bring it back up to boil in 5 to 10
    minutes for rework or additional sessions post inspection/ cleanup on the first run.
    I prefer to watch the pot while it is going, so I never leave it unattended while doing
    cleanup.
    Attached are images of the ingredient packages that are very common. The ingredients
    and process are so simple nearly anyone can make it. If you can make instant coffee you
    can make this blueing recipe!
    
    
    SHOPPING LIST:
    Chemicals:
    5 pounds of Sodium Hydroxide (lye). It must say 100% lye.
    2½ pounds of Sodium Nitrate (Nitrate of Soda).
    2 gallons of Distilled Water.
    
    Equipment:
    
    (1) 16 Quart Graniteware orEnamelware Stock Pot/Seafoood Steamer Pot (size works
    great for pistols). Do NOT buy aluminum. I have seen the enamel type of pots available
    online and in camping supply stores. Other containers of a similar size that are steel or
    black iron will also work.
    
    (1) Propane burner and propane tank setup. I purchased a Turkey Fryer setup. You can
    select any setup and the aluminum or stainless pot will work great for post blueing
    cleaning/boiling to remove the salts. Most of these setups include a pot, thermometer, and
    the burner with regulator and cost from $30 to about $50 from home centers, hardware
    stores, or online.
    
    (1) spool of ductile black iron/steel wire. Must be steel and appear either rusty or black.
    This is found in many home centers and hardware stores. Dip the wire into a degreaser
    to remove oil and diluted muriatic acid bath to prep for use.
    
    (1) steel stir stick for mixing ingredients and stirring the bath to get the salts into solution
    when re-heating. Can be found in home centers and hardware stores. Select a piece 18"
    to 24" in length, 1/8" diameter to 3/16" diameter. You will know when the salts are
    ready when the stir stick starts to blue.
    
    (1) 2 gallon plastic container with lid. Available at home centers in the paint department
    for storing the blueing salts between uses. Let the solution cool, then scrape out the pot
    and put the salts and solution into the pail.
    
    SAFETY: Lye is poisonous, corrosive, and can cause severe burns if not handled
    carefully. The heated solution can burn you. Follow all safety warnings for the chemicals
    and the equipment and always mix in the recommended order out of doors in adequate
    ventilation. Never breathe the vapors, stand up-wind or at a safe distance when possible,
    and protect your eyes from the vapors or splashes. Rinse any solution from skin
    immediately.
    
    MIXING: (All mixing should be done outside in good ventilation). Use a metal 16
    Quart Steamer Stock Pot. Setup the heating source (propane turkey fryer burner).
    
    1. Add 1 gallon of water into the pot.
    
    2. Use a scale to measure five pounds of lye into a container. Slowly add 1 cup at a time
    to the room temperature water. Stir with a steel stir rod until each addition is dissolved
    into solution. If you add too much, it will clump on the bottom and be more difficult to
    dissolve. Continue to slowly add the lye -- the solution will heat up and there will be some
    fumes as the lye dissolves into solution. Avoid breathing fumes and go slowly with the
    mixing.
    
    3. Place the pot of lye solution on the burner and start heating until the solution is warm.
    
    4. Use a scale to measure 2 1/2 pounds of Nitrate of Soda Fertilizer into a container. Slowly
    add the fertilizer to the lye solution in the pot, stirring gently and allowing it to dissolve.
    As the temperature comes up closer to the boil, the fertilizer will go into solution.
    Congratulations, you have just mixed your blueing salts!
    
    STORAGE:
    If you are not planning to use the salts immediately, turnoff the burner and allow the
    solution to cool back to near room temperature. When the solution is not hot or too warn,
    you can pour the liquid into a plastic storage container and scrape the crystals to loosen
    and add them to the plastic storage container too. Rubber gloves and a plastic scraper
    help to completely clean out the crystals in the pot. Wash the residue from the pot with
    plenty of water to dilute and rinse it away.
    
    BLUEING:
    Heat the solution until it reaches a minimum of 253 to 265 degress F and is vigorously
    boiling. Suspend the parts to blue using the steel wire to suspend them from a rod or
    piece of wood across the top of the pot. Let them remain in the boiling solution for 20 to
    30 minutes depending on the steel and the depth of finish desired.
    When you remove the items from the salts they are very hot. Place them into hot but
    not boiling water for about 10 minutes to flush the salts out of any threads or captive
    areas. Dry and inspect. If the item is not blackened to your satisfaction or there are
    areas where it is not even return it to the solution and let it go longer. When final color
    is reached and the part is washed of all salts, completely coat the part in oil (WD-40,
    Gun Oil, Marvel Mystery Oil). I have also submerged the parts in warmed oil overnight
    before hanging them up and letting the excess drip off. I have not seen adverse effects
    from wiping down the parts and admiring the beautiful black finish immediately.
    End of Part 1

    Comment


    • #3
      Part 2
      Code:
      TECHNICAL ISSUES:
      Items can sometimes be covered with a soot -- this seems to be caused by excess heating,
      usually the result of letting the part sit on the bottom of the pot where the burner is
      elevating the temperatures. Other times, it just seems to happen for unexplained reasons.
      Underneath the soot, the finish is black, so let I always let it run and remain patient. After
      removing from the salts I place the part in a warm water bath and use a paper towel, rag,
      or a toothbrush to scrub off the soot. It will scrub or rub off and the finish underneath is
      usually very nice and black. Pipe cleaners will remove soot from small holes or screw
      threads. Once the surface looks clean, you can either return it to the salts for a few
      minutes or continue in a full hot water rinse, dry and oiling process.
      
      Items that do not blue or appear plum colored usually need a little more time in the
      solution. Various steels blue differently, and contaminants on the surface can lend a hand
      in making the process go funky. Usually a good degreasing and return to the solution,
      use of a slightly higher temperature or a longer time will get them black.
      
      If you have touch-ups or areas with defects that you want to fix you can return to the
      solution after corrective measures and a degreasing. I usually do touch-ups immediately
      while the salts are still running so I can assure the results come out exactly the same.
      If you add lots of parts to the solution, it seems to take a little longer than when doing
      smaller bit of parts or touch-ups.
      
      Ken Mays has more extensive experience with the original formula. Practical use is the
      same, but his recipe and mixing is different because ammonium nitrate fertilizer has several
      negatives: First, it gets attention from the FBI and you can end up "a person of interest".
      Second, when adding it to the lye, copious amounts of concentrated ammonia gas are
      produced and ammonia is very dangerous to living things! After his salts are mixed and
      working, things are the same as what I am using, although he reports his solution boils
      at a higher temperature.



      It works, but has a "shelf life" problem - it only worked once for me.

      This formula is nearly identical to a Caustic Soda Brown in Angler's Firearm Blueing and Browning. The difference is that Angler adds some "slaked lime" (which is calcium hydroxide) to the mix, which is for "regeneration of the bath". I purchased some of the lime and will add it to the next batch I make. I used a turkey fryer burner and a stock pot (non stainless) to run my batch. Keep adding distilled water as needed, because it will tend to boil off as you are even mixing the stuff.

      Comment


      • #4
        See if ammonium nitrate blackening will work for you:

        https://bbs.homeshopmachinist.net/fo...ide-experiment

        Comment


        • #5
          I've done it (last time at least 20 years ago) using a 50% Caustic soda solution and ammonium nitrate. It worked very well , however it gasses off a lot of ammonia when first bringing it up to boil, plus there is the inherent danger of a boiling caustic solution and the fumes. Biggest problem here in Australia now, is getting a small quantity of the ammonium nitrate. Before 911 it was as easy as going to the local produce store and buying as much as you needed. Its not really a problem for me now though as I dont see myself needed to do much bluing anymore.
          Peter

          Comment


          • #6
            There was a discussion on this a while back
            Knowledge withheld is knowledge lost

            Comment


            • #7
              Potassium Nitrate can be used instead of Ammonium Nitrate.

              Comment


              • #8
                Here are some results of the method laid out above:

                https://www.hobby-machinist.com/thre...31/post-714003

                Comment


                • #9
                  Originally posted by SLK001 View Post
                  Here are some results of the method laid out above:

                  https://www.hobby-machinist.com/thre...31/post-714003
                  That is what I am looking for. Thank you.

                  Comment


                  • #10
                    Originally posted by redgrouse View Post
                    There was a discussion on this a while back
                    Great thread there too. Thanks.

                    Comment


                    • #11
                      Originally posted by DennisCA View Post
                      Potassium Nitrate can be used instead of Ammonium Nitrate.
                      Does it give the same results?

                      or are there differences in depth of color, reusability, etc?
                      1601 2137 5683 1002 1437

                      Keep eye on ball.
                      Hashim Khan

                      If you look closely at a digital signal, you find out it is really analog......

                      Comment


                      • #12
                        I have never been able to find ammonium nitrate, not even come close, but from what I read it's for all purposes identical to AN based stuff and my results looked like regular hot caustic bluing to me.

                        Comment


                        • #13
                          Been wanting to try it, but haven't had the chance... I heard you could use 34-0-0 fertilizer to do it? I know some green thumbs...

                          Comment


                          • #14
                            Originally posted by redgrouse View Post
                            There was a discussion on this a while back
                            Hey, I remember that post........

                            I am about to fire up my hot blue tank in a couple days. I have a hand full of parts that I have accumulated over the last eight months that I have to do.


                            JL..................
                            Last edited by JoeLee; 09-22-2020, 09:31 AM.

                            Comment


                            • #15
                              Originally posted by junkaddict View Post
                              Going to give it a try. Want to black oxide some small parts. Seen people do it on YouTube, but no recipies. I have a fume hood, and plenty of safety gear, so please no shoot your eye out comments. Best I can find is lye, water, and potassium or sodium nitrate. Just looking for advice and or tips from anyone who has done it.
                              If you don't want to experiment with home brew recipes or are having trouble finding the components you can always get the salts from Dulite or Brownells and probably a few other companies.

                              I wouldn't worry about disposal as you can save the solution for the next batch. Once you get the process down and get good results you'll want to blue everything.


                              JL.............

                              Comment

                              Working...
                              X