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Yet another gold cracking question


#1

Hi everyone,
I looked at several of the old threads on the issue, and I think that my gold is just contaminated… but I wanted to ask your advice in case it’s salvageable.
I normally work in silver and have next to no experience in gold, so I might just be making some obvious/simple mistakes.
Process:
I melted down about 45g of clients old gold chains of varying quality (10-18k, clasps removed)(I assume this was my mistake). Added a pinch of borax and scraped off the slag, then poured it into a warmed/oiled steel ingot mold (10mm round diameter cross section).
Waited a moment and opened the mold and quenched the ingot in water. It looked lovely.
Hammered it with a ball peen hammer down to about 9.6mm.
Annealed to bright orange (with an alcohol & boric acid coating).
Waited till glow had barely gone out of it, then quenched in water.
Ran through flat section of mill taking it down to about 8mm thick. Massive cracks formed.


This was my second attempt, previous attempt was with no hammer forging and smaller slower passes through the mill, still cracked like crazy.

Any suggestions? Or should I just tell the client that, like I’d warned might happen, the gold is too contaminated to use as-is.


#2

Mark,

I think that there were several places that things may have gone awry.
You pegged the number one issue (at least to my eyes) which is mixing carat and alloys—and maybe color?
There was also likely solder in the chains which definitely didn’t help any.
Some may disagree with me but I never quench my ingots, nor do I anneal them after forging them and never to a bright orange.
These thoughts may have nothing to do with the problem but they are the red flags to me. I pour ingots often several times a day in sterling, shibuichi, bronze and various colors and karats of gold, including nickel white.

Hope this helps a little.

Take care, Andy


#3

I don’t quench either. I allow it to cool and then pickle. At this point you may have to send it to a refiner in exchange for fresh alloyed 14k.


#4

Hi Mark
Andy pretty much pegged it but I will add since its been melted most likely 3-4 times already during the original manufacturing and your two attempts the alloys in these mix karat metals specifically the zinc may have burned out. Its a crap shoot when you mix karats sometimes it provides a new color other times this is what happens. If mixing colors even tougher. Also, you didn’t get much cold work into the ingot from 10mm to just 9.6mm before annealing.

Ken
DHF Inc.


#5

You mention that you melted the customer’s gold chains. The issue is the solder that was on the chain links. Never reuse jewelry metal of any kind with solder in it. Sorry but you’ll need to send this metal to the refiner.
Jo Haemer
www.timothywgreen.com


#6

Before you send it to a refiner,try one more time,only this time do not quench,at all. Just let it air cool. If you have access to a rolling mill, try using that rather than hammering. Take your time, and anneal often,to a dull red rather than bright orange. If you get a few small cracks, you can try fusing them shut with your torch. I used to have a client that was a bartender,and she would bring in all sorts of broken chains and single earrings of various karatages with the request that I “melt this down and make me something!” My method worked pretty well.


#7

Old school method, I was in a shop over 30 years ago, they took the filings,
put them in a paper towel with borax and powdered charcoal and melted it into an ingot.
Most reliable method, send out to refiner, with some refiners, loss of 2% of value, and
then use that money to purchase what you need. Refiner I use does not sell or return gold,
I get a check.
I have done that with 14kt yellow and had a usable I got.
White gold, just send out for refining…


#8

I’ll just add one more point to the conversation. I don’t pickle the ingot. And I am cautious of annealing too often. I just taper forged (step rolled) a 14k nickel white (Winter White) ingot poured -as I always do—into an open faced strip mold and then forged with a heavy hammer. After squaring up and reducing in the mill I tapered from about 5mm to 1.5mm over about 2”. No anneals at all at that point. I only Anne Alex before I forged it round in cross section on my anvil.
I think that we over-anneal. Jim Binnion clued me in.
Andy

Please excuse any typos-- curse my clumsy digits…


#9

Hi Mark,

  1. For annealing, heat to a dull red, not a bright orange.

  2. Since you are having trouble, quench in alcohol instead of water after slight cooling. You can use your boric acid/alcohol mixture since it’s handy.

  3. There is one process which I consider basic but no one has mentioned here. I examine the ingot carefully after pretty much every pass for the beginning of hairline cracks. These must be filed out right away!! If it’s a bad ingot, you may have to do this every pass. The rolling mill only compresses the outer surface of the ingot (that’s why we forge it first–to compress all the way through), so the initial stages of cracks are just on the surface and can easily be filed out. It’s like with people–if you catch the disease early enough, you can prevent it spreading and even cure it…:-)…

Janet in Jerusalem


#10

When I recycle old gold I melt it with flux made of 1/2 and 1/2 charcoal powder and ground Sal Ammoniac, then once again with borax. This does a good job and I have’nt had any problems.


#11

Hi Jo,
Id say, almost all machine made gold chain made today is made from a cored wire. this core is in fact a solder so when the chain is passed through a cracked ammonia tunnel kiln it auto solders itself.
Wether this is the problem im not sure as I dont cast gold from scrap chain.
My gut feeling is that cracking is caused by residual oxides that precipitate out at the gold crystal boundaries.
Still needs to be refined. One can get special fluxes ,made in Germany that will do this. I could do the research but would want money to do so. Too busy with my own work.
Ted.


#12

I agree, I’ve successfully used the process you describe…it requires much patience and diligence but I got a 2 oz ingot of melted old gold- from jewelry- mixing in a very small amount of high karats with a majority 14k- processed this way, resulting in a nice piece of 20 g sheet over time, as I did it by hand hammering and with a rolling mill. Along the way, some of the edges of the sheet did crack, but I’ve used all resulting shards and sections as decorative elements, as something of a “signature” , in many of my one of a kind pieces.


#13

I use customer gold very often.

Sometimes you can get cracking because it wasnt poured properly - remelt and try again.
If this doesnt help, remelt and add pinch of sodiu and/or potassium nitrate - it will remove some imputiries and rise karat a little bit.
Dont waste time melting with magical ingridients like table salt/ matches heads/ spider legs and other wired stuff.
If nitrates doesnt help you will need to refine it. Do it yourself or if you dont have proper equipment and/or knowledge - send for refining.


#14

Hey everyone,
Sorry for my slow reply, I’ve been taking an intensive French class and haven’t checked my email/forums for a week! Thanks for your help. I ended up trying once more using a combination of suggestions.
I tried with a much hotter mold to slightly slow the cooling of the ingot, and cast a plate/sheet instead of a rod. Then I air-cooled the ingot without quenching at all. Then pickled it to clean up the top/button a bit. I ran it through the rolling mill in moderately aggressive steps from 4.4mm to about 3mm, then smaller steps down to about 2.4mm. Annealed it to an orange, air cooled, and then rolled the other direction to flatten the sheet and thinned it down to about 2.25mm. No cracking at all yet. I’ve cut out the first ring blank, and the interior of the ingot looked okay at first glance. I’m hoping it still looks fine after actually forming into a ring and polishing.

Thanks again for all your help everyone.