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copper sulfate (sulphate if you will)

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  • copper sulfate (sulphate if you will)

    For whatever reason, I'm currently thinking of trying to make up a solution of copper sulfate. (I know it's also spelled 'sulphate' but let's not quibble over spelling - I'm American.) Reason is I'm about to start grinding HSS tool bits again and sometimes I like to try to grind to a layout line. I can blue up the part and scribe a line but when I start grinding the heat makes the line vanish. I've heard that if I put a tool bit into a copper sulfate solution I will get a strike plate of copper, and that I can then draw layout lines onto that.

    One of the things about modern life is it's really really hard to just go buy chemicals. There isn't anywhere I know of where I can walk in and say "I'd like half a pound of technical grade copper sulfate, please." The easiest way to make up copper sulfate solution - i.e. dump some chemical into some water and stir - would seem to be out of reach. So I'm wondering - what's the best practical way to make up such a solution?

    One thing that occurs to me is that in reading about electrolytic derusting they always say don't use copper for the cathode because it will plate out on your part. So maybe I could do that deliberately, and skip the copper sulfate bath entirely. (Hmm .. it would also be interesting to see where on the part got plated and where it didn't, as a quantitative way of settling the argument between guys who say line-of-sight only and guys who say well-what-about-engine-blocks.)

    I believe I can go to the box hardware store and buy sulfuric acid under the guise of driveway cleaner or toilet scale remover or something. If I put some of that in a glass container and add copper until no more dissolves even when warmed, is the liquid that's left copper sulfate? Like how you might make up ferric chloride.

    It's been a good long time since I took inorganic chemistry ..


  • #2
    I think copper scraps in a jar of battery acid will produce copper sulphate. The blue colour will tell you it is working but I dont know what concentration you would get by this method.


    • #3
      I have an acid bath (battery acid diluted 7 to 1 with distilled water) for pickling copper and brass before soldering. It has been in use for several years and if I put clean steel in it the copper plates out.
      The shortest distance between two points is a circle of infinite diameter.

      Bluewater Model Engineering Society at

      Southwestern Ontario. Canada


      • #4
        You don't need to make it. It's cheap and used for "root remover" in septic systems and drain pipes. Your local hardware store (McLendon's in the OP case - $16 for 2lb)) sells it. Look for the brands that is only copper sulphate - not the "foaming" type. I use it every year or so in my system.

        or.. you can just buy it online 200gm to 50lb...
        Last edited by lakeside53; 01-02-2014, 07:34 PM.


        • #5
          I'd have also gone with AB's 'battery acid & copper wire' route - it works for ferric chloride with HCl.

          Probably obvious, but the toolbit will have to be fairly well degreased to get an even plating of copper. The layer of copper that results almost looks transparent - all grinding marks still show through, which is probably what you're after.

          All of the gear, no idea...


          • #6
            You can get copper sulfate in small (1 lb) to large (50 lb) containers at your local farmers Co-Op. It's used as a fungicide.


            • #7
              Try a pool supply store - used as algicide. I recall a suggestion (one of the Workshop Practice Series perhaps) that a couple of drops of sulphuric acid (battery acid) improves the copper plating.


              • #8
                I'm far off (Portugal), but copper sulfate is very easily bought and very cheap. Used in 1 kg plastic bags, about 4€, they're used 1st) for pools. About 1 kg to 50 m3 water. Algae kills them, and you have a very clean (and somewhat bluish) water for many months. Also 2nd) copper sulfate should spray vines, at least once/year. Same effect, their algae kills their vines, so you get better and more wine.


                • #9
                  I've never tried it but my 1941 recipe book gives a solution of 8 ounces of copper sulphate in 1 pint of water - that's a UK pint of 20 fluid ounces, not a US pint of 16 fluid ounces - with a 'small quantity' of sulphuric acid, applied to a grease-free surface with a piece of clean rag.



                  • #10
                    You can get it from farm supplies too, used to harden hoofs, or treat hoof complaints im told.


                    • #11
                      I simply make a fully saturated solution by dissolving as much copper sulfate as your volume of water will take. The rest will remain on the bottom undissolved. It works with or without acid.

                      But I still prefer Dykem. Much better visualization.
                      WI/IL border, USA


                      • #12
                        If you want to avoid the acid, just dissolve some copper sulphate in distiller water and electroplate the copper on to your part. 1.5 to 6 volts and a decreased Patrick is all you need.


                        • #13
                          OK I'll bite. What happens if you use an increased Patrick??


                          • #14
                            For shop layout use, get some tree root killer, ( Copper Sulphate is also known as Blue Vitrol )
                            Dissolve the crystals in some hot water, add some salt and 5-10 % sulfuric acid ( careful !).
                            This solution will copper plate any bare ferrous (steel) material. The salt and acid speed up the copper coating
                            Last edited by Rich Carlstedt; 01-02-2014, 09:59 PM. Reason: speeling
                            Green Bay, WI


                            • #15
                              Most hardware stores sell copper sulfate by the pound to kill roots in the sewer. You need to mix it in sulfuric acid to make it work. It does pretty good. I had forgotten about it. Thanx for reminding me. Heat the steel a bit first.
                              The stupid EPA may have taken that away too. Dunno, but Peters ACE hdwe in Dewey OK has gobs of it.