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  • Annealing Gold

    Any amateur goldsmiths out there?

    Had to take my wedding ring into the jewellers today to get it repaired.
    I hadn't worn it for about 2 years as my fingers have swollen a bit in the last 18 years and it would no longer fit over my knuckle.
    I knew it would have to be adjusted (cut & enlarged) if I took it in to the jewellers, so I thought I might as well have a go at stretching it myself first, as either way I would be in for a bill of some sort.

    Anyway, searched all over the net for tips on annealing gold prior to stretching the ring, and whilst I found mention of it plenty of times to undo the work hardening that apparently can occur, there were very few tips and some sparse and conflicting advice. Some said anneal at 650degC then air cool, some said red hot and quench, like copper, others said barely even red heat as otherwise the temper hardness increases, and so on.

    So I heated the ring up red hot, and let it air cool back to room temperature. First thing I noticed is that the Gold scaled up very badly, and I mean scale that needs pickling rather than polishing to remove it. Oops!
    Then I very gently started tapping it on the small end of an MT3 centre that I was going to use to stretch it. The ring was mis-shapen anyway after years of being bashed, and after just a few very gentle taps with a nylon hammer the ring cracked. Double Oops!
    The crack was a single straight, clean break, so I decided it was time to let the expert jewellers have a look at it.
    After a wry knowing smile, I was told to come back in 2 days and it will repaired, a size bigger, and gleaming like new all for £30.

    So, I'm curious as to know the correct method for annealing and working Gold, if anyone has done it, and also exactly where I went wrong (apart from not going to the jewellers first )

    Peter

  • #2
    I would like to know the answer too.

    Comment


    • #3
      You are a brave man, I salute you.

      Comment


      • #4
        I cast gold frequently. To soften gold, heat (like you would copper) and dunk in water immediately. If you allow to bench cool, it gets hard, brittle, and most difficult to work.

        Buy an old gold wedding band and have at it. You'll see what I mean.

        Harold
        For those having fought for it, Freedom has a flavor the protected will never know.
        Freedom is only one generation away from extinction.

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        • #5
          Thanks Harold, seems I went completely the wrong way on annealing.

          Do you know if this changes with the purity of the Gold? For example, will 24K or 18K Gold anneal easily like this, but is it different for 14K or 9K Gold with a higher nickel/and other alloy content?

          Peter

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          • #6
            I think it must vary with the gold alloy as 24ct gold will not work harden and can be beaten so thin you can almost see through it (gold leaf)

            Peter
            I have tools I don't know how to use!!

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            • #7
              Hi Peter,

              I cannot answer that question. I work with 18K gold or alloys similar to 18K. I have played around with 10K and it softened quite nicely when quickly quenched. Anything beyond that, I would be guessing.

              Harold
              Last edited by hwingo; 07-10-2008, 07:10 PM.
              For those having fought for it, Freedom has a flavor the protected will never know.
              Freedom is only one generation away from extinction.

              Comment


              • #8
                Originally posted by ptjw7uk
                I think it must vary with the gold alloy as 24ct gold will not work harden and can be beaten so thin you can almost see through it (gold leaf)

                Peter
                I was taught that one can pound 24K gold into foil that was only several molecular layers thick and 24K didn't work harden as we think of work hardening so I think you are right. If not right, you're so close that few would dare to take issue.

                Harold
                For those having fought for it, Freedom has a flavor the protected will never know.
                Freedom is only one generation away from extinction.

                Comment


                • #9
                  When I was a kid in school in the late 60's, I worked at a jewelry factory. Track medals, year pins and the like. With bronze and gold (10 or K) we stamped the design in a blank with a drop hammer and cut off the flash as the first step. If it was a deep or large design one hit wasn't enough to bring up the detail so the work had to be annealed and re-stamped. A wire mesh tray was covered with parts in a single layer. A forced air/natural gas hand held torch was used to heat the workpieces dull red. While still red, the tray was quickly immersed in a cold water/acid solution and dashed around. The were then rinsed off in water and cleaned with a brass rotary brush wheel. The tarnish cleaned off easily, the acid I suppose. My two cents.

                  Comment


                  • #10
                    I suspect the Gold was less than 24 Kt.
                    Alloying agents are like car salesmen, each is different in
                    operation and with different characteristics

                    To resize the ring and make it round, it is placed on a tapered
                    mandrel (with sizes marked) and the ring is peened with a rawhide mallet.
                    The constant contact and forces will grow the ring diameter fairly easily
                    and with symetry. Your use of the tail stock taper was good, but did you beat it downward forcing it to expand on the taper? or did you hammer it all around, forcing it to expand only at the contact point and using the mandrel for shape maintenace? ( This is prefered)
                    A ring taper pin is not as agressive in taper as a MT3

                    It is hard to say what yours was made of ?
                    The fact that you had surface scale is not a good sign of purity.
                    Gold is EXTREMELY ductile, but other metals/alloys are not.
                    The crack could have been a joint that fractured or was soldered at one time.
                    It is rare to get a straight line in nature !

                    Rich

                    Comment


                    • #11
                      Gold is exceedingly sensitive to even slight amounts of contamination. To be truly free of work hardening it must be at least 5 nines pure (99.999%) and even then it can still harden some. Truly pure gold is infinitely malleable as has been said but it must be very, very pure.
                      Free software for calculating bolt circles and similar: Click Here

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                      • #12
                        It is rare to get a straight line in nature !
                        The north shore of Tatlayoko Lake west of us is about the closest I have seen. It is entirely natural even though it doesn't look it.

                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Was this white gold? That stuff is nasty. Work hardens very easily, and is hard (at least for me) to anneal properly. I think it's the nickel they use to whiten the gold.

                          At any rate, heating to barely red, and quenching works for me. I like to quench in water, and then pickle to avoid splashing pickle all over. Then put it on a mandrel. I have one that's nearly square, and it works well for people with swollen knuckles. Then tap the ring with a mallet so that the ring is trapped between the mallet and the mandrel. You don't hit the edge to force it down the mandrel. I normally use rawhide, but I don't see why nylon wouldn't work. The mandrel will mark the inside of the ring if it is graduated, so my graduated mandrel only gets used for measuring, and I have a smooth one for sizing.


                          The break was almost certainly at a solder joint.
                          .
                          Mike

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                          • #14
                            Thanks for all the replies.

                            The wedding band is 9K Gold, which is only 37.5% Gold, with the rest as alloys. When we got married my wife had an 18K band, but I opted for 9K so mine would be a bit tougher, as I knew it would get a harder life in my hands (no pun intended.)

                            Just looking back on some pictures I took as I was going through the process, it is now very clear that the 'crack' was actually a joint, almost certainly in a purer gold solder with a lower melting point. In the picture below, which was taken after heating and before I tried to size it on the MT3 mandrel you can actually see it very clearly, and I'm surprised I didn't notice this at the time.

                            The colour in the picture also shows the degree to which it had scaled up, and this wasn't removable with just a polish (I tried).




                            Peter

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                            • #15
                              That gets me to thinking so I went out to the shop. Turns out the smallest gold material I have is 3" barstock and it's too long to fit on my forge furnace. It's a red gold alloy about 20% copper by weight and some silver and nickel. It's pretty stout and I would't be surprized if it didn't precipitation harden confirming Peter's experience.

                              Maybe I'll saw a piece off the end and conduct some metallurgical experiments.
                              Last edited by Forrest Addy; 07-11-2008, 05:19 AM.

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