Melting Gold Foils

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  • Melting Gold Foils

    I'm going to be melting them gold foils from ram sticks tomorrow so I need to confirm the use of borax.

    Everywhere I look I see borax being used in melting gold, like from jewelers who melt scrap down into ingots and every other form of melting.

    Apparently using a graphite crucible it doesn't need conditioning like a ceramic crucible.

    But everyone seems to use borax on top to reduce the melting point of gold and to help remove impurities which is what I think I would need considering the foils would have some.
    So anyone else have an opinion? what's the worse that could happen using borax if once cooled down the borax should end up at the top of the gold which would just need cleaning off?
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  • #2
    Another question is melting and pouring copper.
    If I melted and poured half a mold of copper and let it cool, then poured another batch on top, would the bar be one solid bar or would there be a seam running down the side?
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    • Geo
      Geo commented
      Editing a comment
      Borax flux can be removed with a prolonged boil in water. The borax is water soluble even after melting. That's the way I clean my melting dishes is to boil them in water. If copper is in the borax, add a few drops of sulfuric acid or even use battery electrolyte (battery acid 10%) to boil the flux in. The borax will dissolve completely. You can use the same thing when cleaning up metal bars that have borax stuck to it. Water will work over time but the battery acid is much faster. Be very careful heating sulfuric acid of any strength. It is extremely corrosive to skin and more so when hot.Wear all PPE's necessary to stay safe.
      As far as copper pours, it will separate into two layers. The only way to make one solid bar from two pours is to keep the first pour molten.

  • #3
    ok thanks Geo, Will see how it turns out later today
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    • #4
      Well that was a flop, It just wouldn't melt.
      I tried with propane and it didn't seem to get hot enough so I tried with map gas and that looked like it was working.

      But after quite some time I got a knife and turned the foils over and the bottom ones weren't even touched.
      so I mixed it around and kept going, it seemed to get red hot and was melting but still didn't look hot enough, just short or melting so I started to think it was the nickel was holding it back.

      So after a long time I finally stopped and put it aside to cool.

      What I have now is crumble, brown & black pieces.

      I think I put too much borax so maybe the black char rocks are borax, the brown? maybe the copper but there's no gold color, just black and brown stones.

      What now? did I completely mess it up?
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      • #5
        Just a thought Ben, considering that these foils are the ones you removed from fingers using a soldering iron, perhaps they have too many impurities in them to melt properly.

        Normally I would use HCl and peroxide to remove the foils, then use AR to dissolve the foils into solution. Then precipitate using SMB. The resulting "gold mud" can then be washed with acids, boiling water or whatever to purify it as best you can. Then you can melt the powder once it is dry. At this stage it is normally recommended to use borax as a flux.

        I understand Ben that you are looking for a way to recover gold using a minimum of harsh chemicals, but I personally believe that whilst it may be possible, it can present its own problems, just like you are experiencing. I look forward to Geo's comments. Cheers
        OKEDEN SCRAP & PM's
        http://www.okedenscrapandpms.com.au

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        • WEEE Ben
          WEEE Ben commented
          Editing a comment
          Yeah maybe too many impurities, maybe just not hot enough, maybe I just burnt the hell out of them.

          Yeah I was just trying an alternative method for scrappers that just wanted a quick solution but when I do start refining myself it will be with a proper setup.

          just can't figure out how it went so badly, I mean, all I have is what looks like rocks and charcoal

      • #6
        Well gold melting point is 1063°c and nickel is 1452°c and copper is 1083°c, I have heard that a alloy of metals will need higher temperatures, propane torches heat up to 1995°c and map gas heats up to 2925°c so going on them figures your map gas should heat up enough, but you need to move the torch around to even the heat up and patience! Good luck Ben

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        • #7
          Ben maybe a couple of problems. Certainly as put by Scooterist, either a propane or mapp torch would be hot enough to melt the three metals. That creates a mess and probably not even a real good alloy. Add the borax to that, and yes it is a mess.

          Other point is the use of borax. When melting gold powder you should heat your crucible first. Going around in circles til it glows when you touch it with the flame. This can take 1/2 hour or so. Then sprinkle in your borax and again heat until the borax is clear and running. Then you add your gold powder and working from the edges melt that.

          But you're talking high karat gold with the powder as compared to a group of three metals etc.
          OKEDEN SCRAP & PM's
          http://www.okedenscrapandpms.com.au

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          • #8
            Seems not hot enough and think the nickel caused some issues too.
            Looking closely there's a lot of foils with gold & copper removed, just a metalic looking foil which may suggest it's the nickel part.

            The gold is probably trapped in the copper rocks so I guess it can still be ok if heated properly, i'll just have to keep it aside until I get a furnace to do it properly
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            • #9
              If you're using propane or mapp you certainly have enough heat. Problem could well be that you haven't pre-heated your crucible. If you haven't then the heat your applying could be trying to heat up the crucible and not all the energy is going into melting the metals. Just a thought.
              OKEDEN SCRAP & PM's
              http://www.okedenscrapandpms.com.au

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              • #10
                You are not getting enough heat to melt it. Move your crucible onto something that will not soak up the heat. Invest in a melting dish from fleabay and a couple of insulating firebrick. The insulating firebrick is soft and can be carved with a sharp knife. I will try to find a pic of what I'm getting at. You can carve a cavity between the two bricks so the melting dish sits in the cavity and the propane torch blows under the crucible heating it from the bottom. There was a guy selling them but they are so easy to make he just stopped.

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                • #11
                  Yep I know of the bricks your talking about Geo.

                  Yeah you guys are right, not enough heat to the crucible.
                  It was a cool day and cool wind was blowing under the crucible so it rarely got a red glow to it, I felt it was sucking the heat as you say.

                  Well it's done now, I will re-set with a better setup and try again but this challenge is kinda stuffed for now, I did the video so you can see my problems, thought the map gas wasn't hot enough either and required oxygen to boost it up but now I believe it's just the crucible was causing the issue.
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                  • #12
                    Use a melting dish, not a crucible. Melting dishes are easier to use and control. You were never going to get enough heat into something that big and thick with MAP. MAP will melt your gold. I used MAP once or twice but then moved onto Oxy/Acet. Impurities will affect your melt. I simmer my foils in full strength HCL and then rinse a couple of times with hot water. If you do this right there is no need to go the AR route. You can just melt the foils and expect approx 98% Au. Russ

                    Comment


                    • Geo
                      Geo commented
                      Editing a comment
                      Sorry Russ but I have to disagree. I will post a follow up on why.
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