Making Gold Solder from Scraps

Greetings and salutations...
I have not done this myself, although I have been looking at getting into a bit of jewelry design and repair...In any case it is my understanding that one can use the next step down in purity as a solder...so in your case, 24 ct would be soldered by the 18 ct, the 18 ct by the 9 ct. I am sure that more knowlegeable folks than me will give a better answer moments after I post this, though (*smile*) Regards Dave Mundt

I wouldn't know but I'm going to guess it starts with copper and zinc additions... I'd look up the compositions of some typical alloys. And wait to see if Abrasha or Harold have anything on the subject...
Tim

The same dealer that sells you the gold and the gold solder should also be willing to buy your filings. Your recovery should be about 90-95% (Harold please correct this estimate). Unless you have your own reprocessing facilities for gold filings, this is your best bet. So now that the value of the gold is out of the equation, here are some reasons for NOT making your own solder.
1. Commercial solders have known karat ratings. Typical is 10, 14, and 18 kt -- 2. Commercial solders with known karat ratings have known melting temperatures. Important when soldering several joints near each other.
3. And this is the most important -- color. There's yellow, pink, white, and green gold and various shades between. If yo make your own solders you're unlikely to get the color right. A yellow gold piece with green, pink, and white solder joints isn't going to look right.
4. Save some money and trouble and don't buy precut solder. You buy solder in a small sheet -- e.g., 1cm x 2cm and cut off tiny pieces as you need them. That way, you can afford to have several different melting temperatures on hand. However, to take advantage of this you will have to buy some really good, jeweler's tin snips. Expect to pay about $50 last time I looked.
Boris

Hi, Heather:
You can make a reasonable solder for just about any carat yellow gold by mixing it with 10-20% by weight hard silver solder, melt it (mix thoroughly), make a bead and roll it out thin. This will give you a solder with similar working properties to the equivalent "hard solder" for that karat gold that you would get from a supplier. But since you are in the UK, please note that this is NOT a "plumb solder" -- use much of it in a piece, and you are likely undercarating and may not pass the assay requirments! I've done it a couple times for repairs, mostly, and once to make 22kt solder when I needed some real quick over a weekend.
If you can find an old book, "Jewelery Workshop Techniques" in a big library, there are a bunch of solder formulas in it.
However, all that said, you are much better off buying solder from a good supplier, as you will get known karatage, melting points, color, and working properties. It's really not worth it to recycle your scrap as solder, IMO. Better to use it in your next cast, or melt it down and make sheet/wire, or just send it to the refiners.
Regards,
Bob Edwards Chromis Designs San Francisco, CA

snip-----> There is no fixed recovery rate. So much depends on the work habits of each benchman that I was never able to make predictions. Results were wide and varied. The lowest recovery rate I experienced, and it was routine for that particular company, was around 20% (of the gross received weight). They included wax, toothpicks, saw blades, dog hair, chicken sandwiches , etc. etc., in their filings. Their polishing waste was worse yet. On the other hand, I had one customer in Arizona that had a diamond cutting machine and kept his filings clean. Very clean. My recovery from that operation was nearly 100%, based on 14K gold, assuming the gold was not plumb, which, at the time, it likely was not. The refining process is quite precise, with very little gold lost to the function, although as the quality of the batch received drops, the loss increases due to drag out. The lost gold shows up in cleanup, so it is not lost.
As a matter of policy, filings are best not re-used. Speaking from the position of a refiner, where you get the opportunity to see the crud included from a bench, the gold would have to experience a considerable reduction of quality, often manifesting itself as porosity in castings and brittle gold that would not roll or otherwise work well.
Unless you have your own reprocessing My experience in dealing with some of the larger refiners left a lot to be desired. They have a reputation for being dishonest, and my experiences with a few of them told me it is a well earned and deserved reputation. The very best scenario for the small consumer is to hope to find a small scale refiner that is trustworthy and stick with him. The negative side is that, for the most part, people like that generally do not offer alloyed gold, nor solders. My operation returned pure gold shot almost exclusively, along with silver crystals, washed and dried, right out of the silver cell. It was beyond my ability to produce any of the alloys or solder on an economical basis, and I was so busy with refining that I had no time to pursue it anyway. On rare occasions I would alloy 14K yellow gold, but preferred not to.
EPA has made it very difficult to buy chemicals for refining, so the idea of a home refining operation is now becoming almost impossible. Further, unless one knows what to do and when to do it, a lot of value can be lost. The worst thing is that the environment in a refinery has the potential to be very destructive. Without very good ventilation and fume disposal, pretty much everything in a room that can corrode does. I kept my fume hood running almost non-stop and still had minor problems. Refining isn't something you should include with any other operation.
So now that the value Absolutely the best advice given. All of it! Virtually all of my customers did exactly that, so it is an industry wide practice. Some cost saving steps simply aren't worth the risk. Making solder from used gold is risking an alloy that won't roll. The quality of gold already in use can be questionable, especially if it is a soldered item to begin with.
Harold

And more. Depends on the color desired, and the sacrificial element used to keep the properties of gold useable. Each refinery has its own 'secret' constituent. Each time gold is melted, it tends to lose its ability to be worked, thus it can not be melted endlessly once alloyed. Smart benchmen melt only the amount needed, and use the small sprue from one casting in the following casting,having pickled it well. That way they work with fresh metals constantly.
Green gold is comprised of gold, silver and copper, percentages varied dependent on the karat fineness. Red gold is copper and gold. White gold has NO silver, only gold, nickel or palladium. Gold and silver combined yield green. Go figure!
Harold

Hi, Harold:
Some white gold alloys DO have silver in them -- I use an 18kt palladium white alloy from PM West that is 75% gold, 15% palladium, and 10% silver. It's a nice, very workable alloy with good white color.
Regards,
Bob

snip------
White gold Hey Bob,
That one's new for me. In all my years of refining I don't recall every consciously seeing it, but it could have easily slipped through the cracks when mixed with old dental alloys and jewelry waste. Dental alloys almost always have at least a trace of palladium. Palladium in solution is hard to miss, being very dark in color, like very strong coffee, unlike platinum or gold. When it's present, there's no mistaking it.
I think what surprises me more than anything is the claim that it works well. Silver is added in combination with the platinum group metals to dental alloys to toughen them. They are not known for their malleability, but palladium and silver combined may not react that way without platinum present. I know that silver destroys the malleability of platinum.
Very interesting report, Bob, and I thank you. I can only assume that the presence of the palladium overrides the ability of silver to turn the alloy green. Regardless, it's always been interesting to me that an alloy that is predominantly gold can be turned white by the addition of only 25% of other elements.
Harold

Yep, copper too (look at the nickels in your pocket - 100% nickel they ain't!). Keeps good color against zinc though, I think it starts turning white with beta brasses. 15% Zn is still semired...
Tim
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

10g silver+8g copper+5gzinc melting together and we call it A formula... For make a gold solder u can use pure gold 70% + A formula 30% or 60% pure gold + A formula 40%. Sorry aboud my bad english