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Thread: Fluxing Lead with Caustic Soda

  1. #1
    Boolit Grand Master


    GregLaROCHE's Avatar
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    Fluxing Lead with Caustic Soda

    I just finished reading the thread « Purifying Lead with Caustic Soda«. I have a lot of range scrap that has a BHN of around 15. I would like some softer lead for making round balls and have often wondered how I could reduce the hardness of some of this lead. Would using caustic soda be a way?

  2. #2
    Boolit Master
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    Sounds dangerous to me,,,, Why don't you offer to trade some of your range scrap for SOWW or pure lead?

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    The older I get, the less and less 'violent' chemicals I use.

    I'd stick with the more tame method you normally use for fluxing, and if its too hard,
    trade it off to someone who wants it for what they do..
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  4. #4
    Boolit Master

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    Having used caustic soda in an industrial application for 20+ years I can tell you it is nasty stuff! Don't mess with crap like this if you don't have to! Trade/sell your range scrap for pure lead in the "Swappin' & Sellin" section of this site, you'll find someone there who'll work with you.
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    Boolit Master
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    from handbook of commercial bullet casting

    Commercial refiners call this "dry drossing," and they usually do it by adding a layer of dry sawdust to the surface of the metal, stirring it well into the metal, and then skim- ming the dross off the metal. After dry drossing, the material needs what is called a caustic treatment. Now this really cleans the metal!
    However, the caustic material, sodium hydroxide, is ex- tremely corrosive and needs to be handled with the utmost care. The correct form of the caustic material is in pellets about the size of a pea.
    You can get sodium hydroxide from most any chemi- cal-supply distributor, and if you decide to add this step, you need to get just enough to cover the top of the metal in the pot after it has melted. Sodium hydroxide is hydroscopic. This means that it readily absorbs water - right out of the atmosphere. And anyone who has worked with molten metal will tell you that adding water causes a most unpleasant re- action. Sometimes, an explosion sends molten metal every- where. Use extreme caution. Always store your sodium hy- droxide in the container it came in when you bought it, and always keep it covered when you're not using it. Always store it in a dry place where no water will come into contact with it.
    To treat molten lead with the caustic (sodium hydrox- ide), spread it on the surface of the molten metal - do not agitate the metal - until it melts. Add enough so that the melted caustic just covers the surface. It will be easy to see, as it will be quite shiny and will look wet. Any water that the caustic has absorbed evaporates after a few minutes and eliminates the possibility of a violent reaction.
    Be extremely careful not to touch the caustic material, either in its natural form or in its molten form. It is ex- tremely corrosive and burns just as readily as a strong acid. For this treatment, the metal temperature should be between seven hundred and eight hundred degrees Fahrenheit.
    Once the caustic is melted, and you're certain that all water has evaporated from the surface, vigorously stir the melted caustic into the molten lead alloy. This stirring is quite important if the metal is to be truly cleaned up. After several minutes of stirring, you can skim off the resultant dross (caustic dross) and dispose of it. Next, although this step is not absolutely necessary, you should remove the caustic chemical from the alloy - spread about half an inch of fine charcoal on top of the molten metal, stir it into the metal, then skim it off. Now, if there is no adverse element in the alloy, it is ready for casting.
    If there is an excessive amount of copper in the alloy, you might have trouble casting anything with it, and you might have excessive amounts of dross. You can selectively remove copper from any lead alloy by adding sulfur while you keep the alloy at liquidus. (Liquidus is that temperature where the alloy is barely molten. It is the boundary between solid and liquid.)

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    Boolit Master
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    Isn't this the stuff the truly sociopathic mix up and throw at people to blind and disfigure them? That was dissolved in water, used at room temp or up to around boiling. Here were talking about the pure chemical on top of molten lead at 700-800°. This is not something I am likely to try at home...

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    Boolit Master Ozark mike's Avatar
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    I dont think it would do anything seeing as i dont think it wont mix with lead and calcium hydroxide i believe is heated to high temps during processing. Dont quote me on this im to lazy to look it up
    Those who would trade freedom for safety deserves neither and will lose both

  8. #8
    Boolit Master
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    Trade it out in S & S. Plenty of people have soft lead they might be willing to trade. Plumbers lead is dead soft.


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    Boolit Man
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    I’m involved in water treatment in which we use a lot of caustic soda. I’m in full PPE when I am working with caustic and I don’t even want to think about adding it to hot lead. Please go with safer ways.

  10. #10
    Boolit Master
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    Caustic soda is used to treat water used for boilers and after all the treatments we used to call it Holy Water. I've seen the safety goggles after a caustic soda explosion. Both the lens's and frame were literally eaten up. thank goodness the guy wearing them got to the safety shower in time. Definitely something you really do not want to mess around with. Alloy too hard cut it with pure lead.
    Much easier and safer than using caustic soda. Frank

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    I currently live in France where there are not many casters, so shipping costs make it unrealistic to trade for soft lead. If someone in France sees this post and wants to trade, let me know.

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    Boolit Master
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    GLR is there any residential or commercial property construction or remodeling being done around your area? I have picked up old lead pipes and roof flashing at job site waste containers and bought at scrap metal dealers. This has always been dead soft lead.

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    The "safer way" of softening (removing all the Sn and Sb) would be to use sulfur. It too creates VERY highly toxic fumes and dangerous by-products. Not recommended at all. It is normally used for removing Zn, but strips most other metals out of the Pb also.

    A 2nd choice I have tested is copper sulfate to remove Zn, but I can not attest it removing Sn and Sb, the stuff that makes Pb harder. In fact, CuSO4 actually adds a bit of Cu to your alloy, creating more hardness that the Zn had.

    Do not go down the path of using caustics!

    Over there, I really do not know what you will do, as shipping over here to the "colonies" is totally out of question cost-wise. Plenty of soft Pb on S&S.

    Good luck.

    banger

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    Boolit Master
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    Sell what you have on egun.de and buy what you need at the same place!!!

    Plumbing and roofing lead is pretty much pure. And old houses are riddled with roof lead.
    Get hold of a plumber/roofer and you're set for good.

  15. #15
    Boolit Grand Master


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    Quote Originally Posted by LIMPINGJ View Post
    GLR is there any residential or commercial property construction or remodeling being done around your area? I have picked up old lead pipes and roof flashing at job site waste containers and bought at scrap metal dealers. This has always been dead soft lead.
    I do collect some pure lead from old pipes, but I just have so much more available at my range. It’s indoor with a concrete floor. I only have to sweep it into piles and shovel it into buckets. I am the only one doing it, so there’s plenty. The pieces of paper targets mixed in make a great flux.

    Jacketed bullets are not allowed, so most people are shooting hard lead at 25 meters from hand guns. That’s where I find the most lead. At 50 meters mostly muzzle loaders are being shot and the lead from there is usually a lot softer, but there’s a lot less of it.

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    Boolit Master
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    It may be extra effort, but with the older building stock on the continent, I can't help but think that soft lead from demolition work could be found readily. Not as convenient nor as plentiful as your indoor source of hard lead, but one or two fruitful expeditions might gain you enough soft lead to last quite a while.

    ETA: And from the descriptions of the hazards of hot caustic soda offered by those in the know, it'd be a much less hazard fraught undertaking.

  17. #17
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    Don't use Caustic Soda to try and clean lead . The stuff is dangerous and you are not going to get pure lead . Just keep the range scrap for use .
    Scrap lead is easy to get at metal salvage yard ... roof flashing , shower pans , x-ray sheathing was used extensively in building construction and turns up often .
    For me getting pure / soft lead has never been a problem ...it's the harder COWW and Printers Type metal that is getting hard to find .
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    Boolit Grand Master fredj338's Avatar
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    Trade for soft. I am sitting on about 500# of pure lead from lead sheathing. I would be happy to trade straight across for harder alloy. USPS med frb for $15. You get 60# worth easy. Not sure they frb from France though.
    If you are trying to remove other alloy, I would crank the pot up to 800# & let the good stuff cook off the top. Dont flux, just skim.
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  19. #19
    Boolit Buddy
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    To answer the question that everyone seems to be wondering: Can I take W/W and remove the SN/SB to get pure lead. In a word, no.
    I think the caustic acts as a 'chemically reactive' flux.

    I did an experiment with W/W. 1000gr of run of the mill (already smelted) W/W plus 200 gr (about 1/2 cup) of caustic and melted them together to measure the results. Once done, stirred for a long while, and then cooled... I had 980gr or so of what I started with plus some fairly dark grey slag. The caustic was also grey colored.
    Whatever got pulled out of the mix, wasn't much as far as weight (less than 20 Gr), but I did notice the resulting ingot was brighter and shinier than what our normal W/W metal tends to pour out like. Haven't tried casting with it so I can't comment on results past that point.

    My first experiment was using some cable sheathing that was near pure but seemed to have some 'crud' in it as compared to really nice pure lead. It definately cleaned that metal up nicely.


    So there you have it. My conclusions are: Caustic (NaOH) works like a hi performance super flux that obviously pulls some contaminants out and provides a cleaner alloy, but doesn't bind or remove the Pb/Sn or Pb/Sb matrix to any noticeable extent.

    I suppose it would be interesting to try that same procedure with some known Zn contaminated alloy and compare.

    ~Jason

  20. #20
    Boolit Master
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    The trick would be for someone with access to have the caustic dross analyzed and find out exactly what is being removed from the melt.There is a commonly used sodium compound of tin,sodium stannate,which may (or not) form ......aqueous hydroxide reacts with zinc,but does this reaction occur in the melt?Enquiring minds want to know?............melt caustic soda ,sand and lead ,and you have a glass,which will also dissolve many other metals in amounts to give colour.....Very Interesting.
    Last edited by john.k; 09-18-2020 at 07:23 PM.

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