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+--- Thread: Gold alloys??? (/showthread.php?tid=10001)
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Gold alloys??? - marsvigilia - 07-25-2007
Does anyone know what the Roman alloyed their gold with and at what percentages. I was discussing 'red brass' C230 15%Zn, and whether it looked like gold, when I realized I had no real idea what Roman gold looked like.
Anyone?
Re: Gold alloys??? - Tarbicus - 07-25-2007
Gold was very high quality, which was one of the ways the silver toledo helmet (which has gold on it as well) was sniffed out as a fake (the helmet's gold wasn't to the same high quality). Obversely, silver was quite poor quality (the helmet's silver quality was too good).
Re: Gold alloys??? - Gaius Julius Caesar - 07-25-2007
So they used 22 carat? 24?
Re: Gold alloys??? - Tarbicus - 07-25-2007
Quote:So they used 22 carat? 24?Oh no, higher I think in the case of gold. I can't remember the exact numbers off hand. When you see ancient gold in museums it's a very deep and rich colour which is an indication of quality I believe, compared to the usual gold we see in general use today. I don't know if that's due to ageing, but I doubt it.
Re: Gold alloys??? - Gaius Julius Caesar - 07-25-2007
Higher than 24? I was under the impression 24 was the highest! :?
Tell me more!!! I ve actueally handled gold ingots from a ship wreck, and thought that was as good as it was going to get!! :lol:
Re: Gold alloys??? - Tarbicus - 07-25-2007
Yes, sorry, you're right :roll: I haven't got the figures to hand, so when I find the time I'll dig them out.
Re: Gold alloys??? - Gaius Julius Caesar - 07-25-2007
No probs! Thought I had lived my life under another falacy!!!
Re: Gold alloys??? - M. Demetrius - 07-25-2007
Quote:Thought I had lived my lie under another falacyWell, that might or might not be true. Yes, of course you can quote me on that.
8)
Re: Gold alloys??? - Gaius Julius Caesar - 07-25-2007
And which lie was that I once lived to lie about? :oops:
Re: Gold alloys??? - M. Demetrius - 07-26-2007
Hey, don't just lie there--this is your story: you tell it how you want to, mate.
:lol:
(no fair editing your spelling after the fact; it messes up the pun. Harumph.)
Re: Gold alloys??? - Matt Lukes - 07-26-2007
24 carat gold is WAY too soft for pretty much any application but making 1 micrometer leaf- for reddish gold, some copper is usually added I believe and this makes it harder and thus a whole lot more useful too for making things...
Re: Gold alloys??? - Marcus Mummius - 07-26-2007
Indeed, lot's of gold alloys were used by the Romans. Often they didn't know the content of the metal they were using. Analyses of objects show that there were some incredibly wild mixtures out there.
Like Matt says, pure gold is too soft for anything but leaf making. But only a slight addition of another metal changes the qualities of gold.
I think that if you add 0.1% lead to gold it already becomes brittle and almost unworkable...
For red gold it is often alloyed with copper, for white gold with silver. This also makes the gold considerably cheaper :wink:
Plinius also describes Corinthian bronze. He writes three kinds existed. One of copper and silver, one of copper and gold and a third livery coloured kind called hepatison.
The gold and silver variety could be made to look like they were pure gold or silver at the surface. This was done by a process called depletion gilding. The object is for example heated so the copper on the surface oxidizes. The object is then put in an acid solution that eats away the oxidation. What remains on the surface is a layer of pure gold or silver. This layer will be a bit porous because of the leached out copper but it can be rubbed closed with a polishing steel. For this process the alloy has only to contain about 30% gold or silver!
The same technique was used by the pre-columbian civilasations to make their 'gold' objects. The process is called 'tumbaga' there. Those spanjards and portugese must have been unpleasantly surprised when they melted the catured 'golden' objects and found out that the largest part of it was copper
Vale
Re: Gold alloys??? - Nerva - 07-26-2007
Oh-oh, hope my wife dosent try to melt her wedding ring :oops:
Re: Gold alloys??? - Franklin - 07-26-2007
Tarbicus is right, the gold found in Roman jewellery is consistently at or around 24 carats, meaning few if any impurities. Matt and Marcus are also correct in saying that pure gold is highly malleable and structurally unsound. In all likelihood, though, the ancients probably saw this as more of a positive than a negative. Gold items were almost exclusively worked cold, a feat that would have been far more difficult if not impossible were gold a harder, more brittle material. As it is, Roman goldsmiths were able to produce some truly breathtaking pieces.
Re: Gold alloys??? - Nerva - 07-26-2007
Lads
Go take a look at this link and it will explain about gold in Jewelery:
http://www.gold.org/jewellery/technolog ... index.html
As for gold as a mineral, it is rarely if ever found in a concentration above 20% as ore. Yest, veins of gold with high concentrations have been found but mostly in Hollywood movies. Let me give you an example, a viable mine runs at about 20g of gold per ton of rock!
The Romans did use high concentration gold, about 96%, for some very limited purposes but most runs well below 80%. As for identifying Roman gold by it's concentration, I'd take it with a bucket of salt. It's far more lightly that 'roman' gold is identifiable by the content of it's impurities as gold will occur with other heavy atoms such as Antimony and even Uranium - Dacian gold will even have a high concentration of cyanide.