My girlfriend and I are wondering what material a particular golden chain she has is made of. We both doubt that it is gold, but it hasn’t tarnished in years (about five), but then again hasn’t been handled all that much in that time.
So what could it be? Gold plated? Some type of alloy with a gold-ish colour? I’d immerse it in water to find out, but I’m not allowed to run around nude shouting eureeka since what happened last time.
Keen to see your answers
Cheers
Luke
Try holding a magnet up to it. That will eliminate some options, depending on whether or not it is magnetic.
Look to see if there are any markings anywhere, probably near the clasp. If there is a number like 14k or 10k it indicates that it is a gold alloy, with the number indicating how much gold there is. 24k is pure gold, 18k is about 75% gold, 14k is about 69% gold, and 10k is about 42% gold (if the numbers I googled are accurate). Other markings like EP or GP indicate that it is gold plated and not solid gold.
There may also be numbers present to indicate the gold content:
8K or 333
9K or 375
10K or 417
14K or 585
18K or 750
20K or 833
22K or 875
The letter P alone means plumb gold, not plated.
GE means Gold Electroplate.
HGE means Heavy Gold Electroplate.
RGP means Rolled Gold Plate.
GF means Gold Filled.
GP means Gold Plated.
The naked Eureka part is optional. Immersion in water is going to be your best bet for determining the density, which in turn will be the most useful measurement for determining the material (especially since real gold is one of the densest of metals, and the densest you’re ever likely to encounter). If the chain is small, though, it might be difficult to get an accurate measurement for the weight or volume. Do you have access to anyone taking a chemistry course? Laboratory equipment could probably measure more accurately than anything you have at home.
This may not mean much.
Tarnish comes from exposure to air, regardless of handling. Unless it is kept in an air-tight container, handling doesn’t matter.
I would still try to be an amateur Archimedes. You don’t need absolute numbers when doing the weighing, the final result is a ratio to the density of water, so ratios all along are fine. Make a tiny set of scales, a few lengths of cotton, and a light beam (about eight inches long say, a bamboo skewer comes to mind) and find something about the same weight as the chain. Just assemble the scales, with the chain bunched up and hanging down on one side, the counter weight on the other, and slide a loop of cotton about in the middle until the scales balance. Mark the beam where the loop is. Then lower the chain into glass of water, move the balance point loop until the scales balance again. Mark this point.
Measure the distances from the two points on the ends of the scales where the chain and the counterweight attach to the two balance points, one in water, the other out. The ratio of the distance from the ends to the balance point is the ratio of the weights of the chain and the counterweight. You now have two ratios, one for in air, the other for in water. Express these as a number (ie the chain weights x times as much as the counterbalance in air, and y times the weight of the counterbalance when immersed in water.
The ratio in air divided by (the ratio in air less the ratio in water) should be the density.
ie, D = x/(x-y) (I hope.)
For the fun of it, I just did the experiment myself with a chain I had from ages ago. I used a knife edge as the balance point and a bamboo skewer. Used some scrunched up aluminium foil as the counterweight. Distances were 139mm , chain to balance and 126 mm counterweight to balance in air, and 144mm and 121mm, in water. This yielded a density of 13.7, which isn’t too far off the mark for what I was sold as an 18k gold chain. Note with something as dense as gold how little the balance point moved - only 5mm. I actually pushed the knife edge into the skewer when it balanced to mark the location so I could get as accurate a location as I reasonably could. Took about 15 minutes.
Just to add, here are some useful densities. 18k yellow gold is 15.58, so my kitchen sink experiment was a little low, but still very much in the ballpark. Given I was only measuring to the nearest mm its not bad at all. Doing it right I should calculate the error, but that is enough for today.
Ho humm, so following myself up again.
I thought I would try to redo the measurement of the chain with more care, using a magnifying glass to check the marks, and maybe be a bit more accurate than to the nearest mm. So this time I got 15.3, which is unreasonably close to the correct value of 15.58. So inspired by the result, I tried a pendant of dubious provenance sold to me as 9k gold. Given how it has tarnished I wasn’t exactly sure what the answer would be. Well, one feels a bit like the ancient Archimedes for real now. Density of 11.2. Almost exactly right. (One should note that the number of significant figures above are probably unreasonable. Its 1:30 am, and time for bed, so I’m not working out the errors.)
Did you miss the part of the OP where he said it was his girlfriends’ chain? Naked is not optional.
Absent markings and physical tests (i.e. 24K is softer and less durable), do the various alloys differ visually? Could someone with a modicum of experience look at a chain or ring and guess with any degree of accuracy whether they were looking at 10K or 18K? If not, is there any reason for people to buy different values? Is it a prestige thing like diamonds?
Lol. Well guess doing a bum run is on the cards after all.
Ditto the above question.
The part about the different stamps or engravings on the chain were interesting, if not helpful in this case: HWT and T22 is all that’s on there. However I might be wrong as HWT could be SW3 or SWS or SVS. It’s really small and while I have excellent eyesight and a magnifying glass it doesn’t get any clearer when enlarged: the stamping isn’t too clear.
The colour itself is a darkish gold, almost red-ish or pinkish.
I’ll try weighing it tomorrow on kitchens scales and using kitchen measuring jugs and seeing if that helps.
Thanks for the excellent replies so far guys.
Cheers
Luke
I disagree. Oxidation can be worn away by friction from handling. There can also be reactions with salt and oils on skin. I have some silver with tarnish fingerprints on it.
's because what t-bonham is talking about is oxidation. “Tarnish,” at least as it relates to silver, is generally silver sulfide.
Very clever experiment, Francis Vaughan. I was worried about things like meniscuses in measuring the displacement, and the precision of any scale available to the OP, but comparing the buoyant force to the weight like that gets around those problems.
I think you could go to a shop that buys gold, try to sell it, and see how much they offer you.