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Thread: DIY gold alloys

  1. #1

    DIY gold alloys

    Anyone know anything about alloying gold, or alloys in general? I'm completely, totally, 100% new to casting so I have some super basic questions...

    The alloy I need to make is mostly gold plus some palladium and some silver and zinc - the finished alloy has a melting point near 2000F. The pure palladium has a melting point over 2800F which I probably can't reach. If I bring the gold/silver/zinc up to, say, 2100F will the solid palladium dissolve into the mix and form the alloy? Or do I need to heat past the melting point of the Pd?

    Also do I need to stir the alloy to mix the metals or does it kinda mix on its own?

    Thanks.

  2. #2
    I don't believe you will need to stir. infact, I believe you should NOT stir...

    I believe the Pd will dissolve once the others are melted.

    I believe a big problem you will have is the Zinc boiling off. Not sure what Zn in doing in there... what is the application?

    I don't know about lot about gold alloys, but I think silver and copper are used a lot.

    My thoughts...
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  3. #3
    Hell if I know what the zinc is doing... great point about the boiling point, hadn't thought about that. I'm making an engagement ring for my girlfriend; I got it into my head that I just HAD to make it myself because I have some small (5g) gold bullion thats a kind of heirloom.

    It seems that alloy composition for jewelry is treated as a trade secret nowadays - most are sold already-alloyed under brand names like "X1" and "Palladium UltraWhite" etc. Not to be condescending, but I've also found that many jewelers/online jewelry forums are full of grumpy unhelpful people that only want to talk about the purity of their art and tell me I should leave things to the experts. So I'm a little short on info for the "proper" composition.

    One good site I did find was this one: http://www.azom.com/article.aspx?ArticleID=2372 It has several alloys listed, many with a trace of zinc.

    ?

  4. #4
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    Quote Originally Posted by Undercover999 View Post
    Hell if I know what the zinc is doing... great point about the boiling point, hadn't thought about that. I'm making an engagement ring for my girlfriend; I got it into my head that I just HAD to make it myself because I have some small (5g) gold bullion thats a kind of heirloom.

    It seems that alloy composition for jewelry is treated as a trade secret nowadays - most are sold already-alloyed under brand names like "X1" and "Palladium UltraWhite" etc. Not to be condescending, but I've also found that many jewelers/online jewelry forums are full of grumpy unhelpful people that only want to talk about the purity of their art and tell me I should leave things to the experts. So I'm a little short on info for the "proper" composition.

    One good site I did find was this one: http://www.azom.com/article.aspx?ArticleID=2372 It has several alloys listed, many with a trace of zinc.

    ?
    do some digging and find you a book on jewerly that will give you some background info on alloying gold. I would leave the zink out and throw in a touch of tin. What color is the palladium going to bring to the alloy, the tin will lower the karat but harden the gold to make it more durable same with the silver it will lower the total amount of gold but not really change the color of the metal unless you throw in a bunch of it. Have you checked out the online jewelry catalogs to see if you can find a wax ring in the shape that you have in mind.

  5. #5
    Quote Originally Posted by dallen View Post
    do some digging and find you a book on jewerly that will give you some background info on alloying gold. I would leave the zink out and throw in a touch of tin. What color is the palladium going to bring to the alloy, the tin will lower the karat but harden the gold to make it more durable same with the silver it will lower the total amount of gold but not really change the color of the metal unless you throw in a bunch of it. Have you checked out the online jewelry catalogs to see if you can find a wax ring in the shape that you have in mind.
    The palladium is a bleaching agent (like the nickel in older white golds) - the point is to turn it white as far as i know.

    I've got my waxes all set - I made a design based on what she typically likes and I have a little homebrew CNC machine that I used to cut some molds.

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  6. #6
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    Uh, I have to ask: What's that mold made of? Because it looks a lot like wax, and a wax negative is going to be kind of difficult to use (unless you want to make your ring out of investment!) It's possible to make a negative into a positive with the help of some plaster and/or RTV silicone (or alginate, whatever) intermediaries, but I'd think it would be a lot easier to make a positive in the first place. If the mold is something into which you can inject wax directly, and you're already set up for that, then feel free to ignore the above.

    No, you don't have to reach the melting temperature of the Pd, though you will have to reach significantly above the melting temperature of the final desired product (if it melts at 2000F, then it'll need to pour about 2300F based on my experience with jewelry casting copper and sterling silver). Jewelry casting, since it uses such small amounts of metal, is frequently done with oxy/fuel torches, which don't have a problem reaching whatever temperature you want. You will have to use pressure (centrifugal, steam, vacuum) assist to fill the mold.

    The flame will most likely provide all the stirring action you need. If you want to stir gently with something suitably inert, it won't hurt anything, but don't introduce any metal tools to the melt!

    I don't have experience with gold in particular, but zinc is frequently a deoxidant/degassing agent (when the gas in question is oxygen, at least). Gold shouldn't be susceptible, and I don't think palladium is either, but silver is. You should only need a smidgen of zinc to do this, and it won't boil off at any significant rate once it's in the alloy at such low concentrations. Zinc can also be used in larger amounts as a general alloying metal, and there it *will* boil off as usual.

    Also: I don't know what's up with that link, but I was kind of expecting their recipes to all add up to 100. It makes me think something's missing when some of them do and some don't.
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  7. #7

    What are the molds made of?

    What do you need zinc for? won't you like to do a k series gold alloy? 22k, 18k, 14k etc.
    I found that trying to find what I need and then make it work with what I have, is more trouble than designing what I want and doing it.
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  8. #8
    Just use alluminium bronze and keep the gold, at least to practice with!!

    Donk
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  9. #9
    lol donk

    The k is not an alloy per-Se... it's just a notation of how much of the alloy is pure gold. so 24k is pure gold, 12k is 50% gold.. the other things in it could be anything... like white gold could be 14k and yellow gold could be 14k but both very different alloys.

    One thing to keep in mind is that this is by weight. Alloys are by weight.. gold is HEAVY!

    I'd use a nickel and some gold.

    Any time I have melted gold it was in one of those little dish like crucibles and I used a bernz-o-matic. takes a minute to get things up to temp, but it's super easy. Use some borax to flux things, just a dash or two...

    The main thing to keep in mind... it's easier to alloy than to UN-alloy... to do that, you have to bring it down to 6k and then dissolve and reclaim. Not hard, but not as easy as throwing some metal in a pot.

    SUPER cool project and I would suggest what anon says. CNC the POSITIVE in wax and then do standard investment casting... might have to do a centrifugal casting... I used a machine once that sort of "threw" the metal into the mold. Sort of like a spring loaded arm. You put the molten metal in a lil pot and had a tube that the metal ran down into the mold once the arm flung.

    I'd also suggest doing 18k
    Last edited by GypsyTinker; 11-30-2011 at 10:42 PM.
    Knowing how to make something is far more valuable than knowing where to buy it...

  10. #10
    Quote Originally Posted by dallen View Post
    do some digging and find you a book on jewerly that will give you some background info on alloying gold.
    ... sometimes in this day and age I forget to look beyond the internet. :-| Good advice. I have a book on its way to me now called "The Jeweller's Assistant in the Art of Working in Gold: A Practical Treatise for Masters and Workmen, Compiled from the Experience of Thirty Years" which is a reprint of a book written about 1900. The TOC claims that it has the info I need, though I do worry that perhaps it will be out of date; I wonder when palladium came into use for jewelry...

    Also I found this book available online "The Scientific American cyclopedia of formulas" from 1919 that offers this comment for palladium-gold alloy:

    Palladium - 1. - An alloy of palladium 20 parts, gold 80, is white, hard as steel, unchangeable in the air, and can, like the other alloys of palladium, be used for dental purposes.
    2. - Alloys of gold, copper, silver, and palladium have a brownish red color and are as hard as iron. ... The composition used in the Swiss and English watch factories consists of usually of gold 18 parts, copper 13, silver 11, and palladium 8.
    The funny part is that last alloy (which is said to be brownish/red) works out to be 37.5% gold, 12.5% palladium, 23% silver, and 27% copper. That is strikingly similar to an alloy on the previous page which was claimed to be "white gold" at percentages of 58.5% gold, 5% palladium, 32.5% silver, 20.5% copper, and 1.4% zinc. I am very suspicious of white gold alloys with high percentages of copper...

    Hoover and Strong (http://www.hooverandstrong.com/categ...pecifications/) sells two palladium white alloys and I can use the density info they give to tease out the composition of the 18kt version (which is supposed to be their whitest) - its 75% gold, 24.5% Palladium, and 0.5% copper.

    I can't calculate the proportions of their 14kt version because it has three extra metals instead of two. But the density they list is almost exactly the same as the density for the 14kt nickel-free alloy listed on the Azom page. Soooo thats a clue.

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