Annealing Gold

[Peter Neill]

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

[tattoomike68]

I would like to know the answer too.

[Al Flipo]

You are a brave man, I salute you.

[hwingo]

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

[Peter Neill]

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

[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

[hwingo]

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

[hwingo]

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

[GKman]

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.

[Rich Carlstedt]

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