What happened to my gold? Aargh

[Jellybaby]

I’m not a refiner, I’m a jewellery maker & ive been melting scrap to make wire for rings since the beginning of the year. It was all going really well.

Recently to save the faffing of scraping borax off a solid cone, I bought a 1 kg tub of borax sodium tetraborate decahydrate, and I think because I suddenly had a lot, I used too much.

I had about 20g of 9ct gold to begin with, and I melted it with a spoonful of borax, but it wasn’t a normal pour of solid metal, it was followed by drips of molten glass. As it didn’t work right I tried it another two times, and the glass glaze in the dish got darker and thicker each time. I think I may have got a bit of the casting sand in there as well as I did it over.

The ceramic dishes now are trashed, and the gold is so brittle, the thin pieces I can snap like a matchstick, so it’s become unworkable for wire. It won’t pour well.

I think I have somehow blended the gold with the glass. It’s a bit of a disaster. The quantity of gold certainly seems a lot less though I don’t have scales to hand. I don’t know what happened but I’m pretty certain I’ve wrecked the gold. And I think that there’s gold in the glaze on the dishes. I have tried to get it out by adding bicarbonate or soda, with some success on one dish.

Can anyone suggest what I could do next? Thanks

 

[jimdoc]

You should post some pictures.

 

[FrugalRefiner]

In general, remelting karat gold will eventually lead to problems. When heated to melting temperatures, the base metals in the karat gold begin to oxidize. This leads to problems in the quality of the alloy such as porosity. The flux in your melting dish is becoming darker each time you remelt because the base metals are oxidizing and reporting to the flux.

If you want to be able to reuse your scrap, you will need to refine it (or pay someone else to refine it for you). You can then add fresh base metals to the refined gold to make your own karat gold.

Dave

 

[rickzeien]

This is one of the reasons I love this forum.

Outside of serving an apprenticeship, attending technical college for a long time or some extreme trial and error process, how would anyone acquire this knowledge.

Thanks to all who answer and thanks to all who question!

Sent from my SM-G950U using Tapatalk

 

[nickvc]

Another problem you could have caused yourself is if you used castings as 9 carat casting grain contains silicon which will not allow the normal ductility gold has allowing it to be rolled or drawn, silver is normally just silver and copper in the alloy so it should be fine to work if annealed, 9 carat alloys have gold, copper, zinc and sometimes silver plus silicon if castings so there are more things to cause problems so as Dave advised refining may be the only way to make it useable.

 

[anachronism]

As Nick and others have quite rightly pointed out you don't have "good" 9 carat gold any more.

Refine it back to fine gold and then add the required base metal to make it 9 carat again.

 

[Jellybaby]

Thanks, I suspected that I would just have to scrap this particular gold. I don’t work with acids as I’ve got kids around & don’t know much about metallurgy so re-amalgamating it back into 9ct would be beyond me. Am I right in thinking it’s brittle as it’s contaminated with glass or has the ductility gone due to altering its structural composition through oxidisation?

I have successfully melted 9ct and reformed into rings a few times already and will have to again as I have taken on some commissions to reform customers old 9ct jewellery into new wedding rings.

As we’re staying at home I thought I could just get on with these projects. I really would like to ensure I don’t screw up anyone else’s gold.

Was the problem simply too much borax? If I use a new dish with very little borax and pickle the gold to ensure it’s really clean, is this my best chance of success of keeping the 9ct as 9ct? I’m using a oxy-lpg gas torch so the temperature is not regulated.

Thank-you for your replies and I have tried to post a picture.

 

[Jellybaby]

The pickle is sodium bisulphate, vitex safety pickle which removes surface fire stain and oxides

 

[anachronism]

Hi Jelly

Any decent refiner will get you your gold back. 8) 8)

 

[Jellybaby]

Ta, I’m packing it up now ready to post tomorrow.
Just concerned in case this happens again when it’s not my own gold...

 

[nickvc]

Don’t try to use any castings that are 9 carat as they almost certainly will have silicon in the alloy which will cause cracking when rolling or drawing, sometimes I know it’s more about the sentimental value than the actual value of the gold to customers so point out this problem to your customers when they give you pieces to use, old wedding bands can usually be used as they are stamped or cut from tube and this is usually what most people want to use from my experience.

 

[Jellybaby]

Thank-you. Just so I understand what happened, have I accidentally refined down the gold to a higher carat?

There was definitely less metal left after. Theoretically could I add some silver and make it back into a lower carat alloy with more volume?

 

[Jellybaby]

Or could I add in copper to make rose gold? I realise that alloying is the opposite of refining but if I have accidentally taken out the silver and copper from my 9ct (?) if I add them back into the crucible do I then have a ductile, annealable metal that could be assayed as 9ct?

 

[FrugalRefiner]

You're still going to have problems due to oxidation because the gold, and whatever alloys remain with it, has been melted multiple times. Some of the oxides ended up in your flux, but others remain with the gold.

Dave

 

[Jellybaby]

thank you Dave, my latest metal has only been melted once. I scrapped the last lot.
Is there any way of reducing the oxides? Are they what make the metal brittle? There are deposits of black stuff on the reduced gold that wont easily come off either with pickle or scrubbing and I guess it’s oxide.
I’m using an lpg/oxygen flame so it’s not a clean process. But I’ve kept the metal very clean and used a new crucible, which has been left orange.
I think I’ve lost 2-3g of metal in the melt. I just can’t work out what I’m doing that’s buggering things up as I have done the same thing half a dozen times a month ago with no problems such as reduced metal or brittleness.

 

[anachronism]

Ta, I’m packing it up now ready to post tomorrow.
Just concerned in case this happens again when it’s not my own gold...

Didn't get packed and sent?

 

[Jellybaby]

The first ruined lot was sent to the refiners. There’s only one refinery that was still open, so I’m not expecting to hear back soon.

I started with some ‘new’ 9ct red gold today, (1 bracelet, 1 wedding ring) and I was praying that it would work ok for me this time to make some wire. It worked ok several times before just except that last time. But again it didn’t work out well. This lot has only been melted once, so I’m now thinking I could maybe add in some silver & copper, a couple of grams which is what I’ve lost in the melt.

I’ve now done some more reading around the forum, and I’m thinking maybe I’m using too much oxygen in my flame. Also I read you can add reducing agents (flour, soda ash) into the flux and am wondering if this would be helpful...

Bearing in mind that this time I have only melted it once, can I save it? I need ductile, non-brittle wire at the end. It doesn’t matter about surface porosity, its for a rustic ring. And I need a specific volume of wire so if I’ve taken away some silver and copper, I have both metals available and could easily add some back in.

Any help would be honestly very appreciated

 

[Jellybaby]

I also wondered if pickling the gold to clean it in sodium bisulphate is putting unwanted salts into my crucible, I’m not much of a chemist, I’m just trying to understand what’s causing me these problems I didn’t use to have

 

[Shark]

Since you mentioned using lpg for gas, is there any chance you have changed brands or had a bottle refilled since your last try? I have only had it happen once, but I have had some bad lpg gas that about drove me crazy before trying another bottle that cured the problems. Mine weren't as bad as your seems to be judging from your dish's, but they were close. I have also seen that heavy red/purple look when melting some very dirty silver with a lot of oxides in it.

 

[Jellybaby]

I haven’t changed the gas but I think I could be getting near the end of the bottles as I have had some problems with flame consistency, sometimes it’s got less oxygen half way through & sometimes going out.
I’ve just been cleaning the metal again and thinking about adding some silver & copper, and I can see that the silver has definitely separated out yesterday as one of my resulting blobs is silver coloured, all my inputs were 9ct rose gold.
I am completely perplexed as to why the alloy is separating like this.
The only real change I can pinpoint is the new borax flux. I am going to use my old cone scrapings as before.