identifying whether or not a piece of jewelry is gold

I have a few gold colored pieces jewelry that I think may be gold but
am not entirely sure. Is there any way I could determine, for sure?

Would such a test distinguish between stuff that's been gold platted
and stuff that is solid gold?


--
Posted via a free Usenet account from http://www.teranews.com

yawnmoth wrote:
I have a few gold colored pieces jewelry that I think may be gold but
am not entirely sure. Is there any way I could determine, for sure?

For sure? Take them to a jeweller.

For a good approximation, find an accurate weighing scale, find an
accurate way of measuring volume (displacement bottle?), and do some
web searching on how to measure the density (aka specific gravity) of
these pieces, then compare it to the density for standard gold alloys.
It's not _easy_, if they're small pieces and you're just using the
kitchen sink, but it is possible.

I don't think there's any other way that's likely to give better
results, such as colour or scratch needles, without even more time and
trouble.

Most "gold" jewellery has some gold in there, but it's often very
little (low karat gold) or merely plating. 9kt and plate should be
identifiable and distinguishable by this technique.

On Fri, 24 Nov 2006 11:28:56 -0800, in rec.crafts.jewelry "yawnmoth"
wrote:

I have a few gold colored pieces jewelry that I think may be gold but
am not entirely sure. Is there any way I could determine, for sure?

Would such a test distinguish between stuff that's been gold platted
and stuff that is solid gold?


The classic way to determine this is as follows:

first, perhaps with a magnifier, examine closely the worn parts of the metal, ie
where chain links rub together, or exposed edges and corners have been worn.
Those are places where a thin gold plating, or even, with more wear, a layered
metal like gold filled, might expose the underlying base metal to just visual
examination. The underlying base metal is often a brass or bronze,
distinguished from the gold alloys by often having a duller look, or a different
color. In some cases, corrosion from perspiration, water, etc, will have left
traces of green corrosion products, either on the base metal, or in creases and
crevices of the article nearby.

Someone who's really familier with gold can usually detect the plated and filled
stuff just by visual examination.

If you're not sure, or think it's passed this exam, then the next step requires
a bit of nitric acid, and a small needle file or similar tool. Small amounts
of the acid are best obtained from jewelers supply shops (or similar, on ebay).
You don't actually need the whole array of gold test acids for the basic
decisions, but especially if there's a chance it's higher karat gold (18K, for
example, or higher), then you may need a test stone. This can be the
manufactured gold touchstones, or a piece of unglazed black or dark ceramic
tile, or a bit of black sawn stone like slate or basalt. You need an unpolished
surface.

Anyway, the first step is to put a drop of the nitric acid in a small notch
which you've filed in an inobtrusive portion of the item. Only needs to be deep
enough to cut through any plating or filled layer. The acid can be a 50 percent
dilution, still pretty strong, or stronger. Normally, one uses a pretty
concentrated solution. You only need a small amount for each test, so don't buy
a large bottle.

If the metal is plated or filled, or just plain base metal, the acid in the
notch will bubble up green from the copper based base metal that's usually
there. If the metal is karat gold, under 14K, then the gold exposed to the acid
(in the notch and out, no difference) will slowly darken to a brownish /blackish
stain. The lower karat, the fast it reacts. 14K will only slowly darken, if at
all, and higher karats won't react to plain nitric acid. If there's no reaction
at all, and the metal stays bright yellow, then it's higher karat than 14K.

To more precisely determine karat, you need to do a touchstone test. Here you
rub the gold item on that black stone, back and forth enough to leave a pretty
substantial mark. Now, if you've got comparison metals, which can be bits of
jewelry or gold of a known karat, or a set of gold test needles which are a set
of bits of gold of each of several karats, then you place another streak of the
needle or sample that's the same as you suspect the unknown to be.

Now put a drop of nitric acid across both streaks. If there's a reaction at all
(similar to what you saw on the sold metal) you can compare the speed with which
the reaction takes place. If the unknown reacts more slowly than your sample,
then it's higher karat. If faster, then it's lower. Several such tests may be
needed to determine which karat the unknown is. If the karat is high enough
that nitric itself dosn't do the trick, then to one edge of where you've spread
the drop of nitric, sprinkle a few grains of ordinary table salt, which adds
chloride ion to the nitric. It forms in essence, a very dilute version of the
mix of nitric and hydrochloric acids known as aqua regia. With the addition of
a bit of sale (mix the acid drop around so both streaks are now equally
affected, you should see the gold reacting to the acid/salt mix. Again, the
speed of the reaction with the unknown, compared with that of the known sample,
tells you what you've got.

The other way to do these tests is to buy a small set of calibrated test acids.
These are used in much the same way as described above, except that the strength
and formulation of the acids are calibrated so that each marked grade of acid
will only react with a gold standard up to a certain point. Usually they're
made so that, for example, a 14K test acid will affect any lower karats, but
not 14K itself, or will do so very very slowly. These can be used either by
putting the acid right on the gold, or with a touchstone streak. On the streak
it's a bit more accurate, but often you don't need to know it that precisely.

You can also buy measuring tools, meters, that are used with several types of
electrolyte gels, to measure the gold content. They're pretty accurate, and
generally easier to use than acid testing. But acid testing is, in the hands of
someone experienced with it, just as accurate, maybe more so, and you can get
the test acids needed for a small fraction of the high cost of those electronic
testers.

Another poster also suggests hydrostatic measurement, to determine the density,
or specific gravity (different words, pretty much the same thing) of an item. If
you've got an ACCURATE scale for small weight divisions (say tenths of a gram or
smaller), and your item weighs enough to make the measurement meaningful, then
this is also a useful test, though easier to fool, since there are a number of
ways in which a jewelry item's weight or apparent density may not match what
it's karat should be (such things as gems set in it, hollow structures, or
certain other materials that can throw off the apparent weight.

And don't discount the value of actual markings. Most gold jewelry, when new,
is marked with various markings to indicate who made it, what it's made of, etc.
While these can be worn off with time, and partial pieces of broken jewelry may
not have the marks, they are still very useful clues to start with, if they're
there. and if an apparent complete piece of jewelry has no markings whatsoever,
that's an indication to precede with caution. Marks can be worn off, or removed
by various repair operations, but they can also be missing if the item simply
isn't precious metal. Likewise, items can be fraudulently marked as karat gold
when they are not, or are a lesser quality. But most of the time, markings are
a pretty good indication of what an item is.

Hope that helps.

Peter Rowe

"Peter W.. Rowe," wrote in message
...
Anyway, the first step is to put a drop of the nitric acid in a small
notch
which you've filed in an inobtrusive portion of the item. Only needs to
be deep
enough to cut through any plating or filled layer.

As usual, Peter's reply is accurate, concise and helpful. But I feel I need
to add to the section on file notching.

I have spent the last 25 years doing antique jewelry repair. A large and
annoying portion of those years have been spent repairing the damage done by
scrappers.

The worst of which involved a marked 14k pocket watch case with multi-color
overlay.

Some bright spark had put a deep scar in every different colored piece of
gold with a tricorner file. Frankly, even it had been made out of gold fill,
it would still have been worth twice it's weight in 14k, had it not been
disfigured.

I still have nightmares about that one.

Be careful. Some jewelry has value in excess of the gold contained. If you
must take a file to a piece, find a spot where it will not be obvious or can
easily be repaired or polished out. A healthy cut with a flat file on the
back of a ring shank or the top of a chain link, is a lot easier to fix than
a small vee grove in the wrong place.

Paul K. Dickman

On Sun, 26 Nov 2006 10:35:28 -0800, in rec.crafts.jewelry "Paul K. Dickman"
wrote:


As usual, Peter's reply is accurate, concise and helpful. But I feel I need
to add to the section on file notching.

Pauls comment on notching is right on, and bears a further comment. Remember,
when testing jewelry, that part of the idea is not only to establish the value
of the metal, but not to damage the value or physical integrity of the jewelry.
cutting into the item with a file is only needed if one suspects plated or gold
filled wares, and as I noted, often this can be determined simply visually,
without needing to file notches. And as Paul notes with karat gold jewelry,
some antique or otherwise rare items, even if made in gold filled or even plated
metal, can have significant value. Going wild with a file can do a lot of
damage to that value.

This is, of course, where some experience with jewelry is helpful. A novice to
jewelry work, could easily not realize that a piece has collector value beyond
it's gold content. So you novices out there are advised to do your research
first on your wares, before digging into things with a file.

And remember, when you do file a notch, it needs to only be deep enough to cut
through a layer that is thinner than tissue paper, and only needs to be wide
enough to see with a magnifier. You don't need a deep canyon. Just a very
slight cut into the surface. And many times, instead of an obvious notch, you
can find a corner, edge, or somewhere where you could either file just a tiny
flat, cutting into the corner, or where normal wear has already made that cut
for you, thus needing a less obvious mark to be made.

It should also be noted that the electronic gold testers claim to be able to
detect gold plated and gold filled wares without filing that notch, since the
electrochemical characteristics of the metal depend on more than just the
surface. However, I cannot claim expertise in the accuracy of these things,
since I've never felt it necessary to spend hundreds of dollars for a function I
already know how to do with stuff I've already got around. But the
manufacturers claim high accuracy. No doubt this can be trusted to the same
degree as claims made by other manufacturers... :-) (Actually, some independent
tests have shown the machines to be reasonably good, on a par, approximately,
with acid testing. But those evaluations were for testing solid metal, as I
recall, not plated or filled wares.)

And a note to Paul, if indeed you spend a lot of time repairing antiques with
things like filed notches, well, my friend, you NEED to discover laser welders.
They fix that sort of thing with ridiculous ease, even with multicolored metals,
platinum, or very fragile pieces. The things are costly, yes. But if you've
got enough volume of work that will benefit from the technology, the machines
can quickly pay for themselves in increased productivity, and simply the ability
to do both superior work, and jobs which previously were not possible.

I have a pocket watch that presented a somewhat similar problem. I actually
bought it back during the gold run up in the early 80s, from a shop that opened
up near our store to buy scrap gold. Those idiots were only interested in
buying gold as scrap, with no knowledge of other values of what they were
buying. While they did know to salvage diamonds, everything else was scrap to
them. So I worked out a deal. Before they got wild with the stuff they'd
bought each day, they'd give me the chance to unset stones for them properly.
That gave them their diamonds undamaged, and I'd get to keep the colored stones.
Most were junk, but a few were not, and well paid me for my efforts. But then
there were also a couple pocket watches. I convinced the guys not to rip out
the movements and scrap the cases, tossing the movements, but rather to sell me,
at whatever small profit they needed, the watches whole. Most went to a watch
dealer who happily took them off my hands at a profit for me, and a good buy for
him. (One can only shake one's head sadly at the folks who had ignorantly sold
these things as scrap gold) But a few, I kept, including one of these mens
hunter cases with lots of multicolored gold work. Gorgeous. Needed a bit of
repair, some touchup here and there, and importantly, repair of all the hinges
fitting the varous parts of the case together. While at this point in my
career, I could do that with a torch, back then, frankly, I wasn't good enough.
But didn't know it. Needless to say, the hinges didn't come out so well. So
the thing got put in the back of some corner for a later date and forgotton,
where it sat until a few years ago when I got a laser welder. With that, it
took me less than a half hour to fully renovate those hinges, and do the other
touch up work the case needed. A new crystal, a bit of business for a
watchmaker friend of mine who serviced the undamaged and working movement, and
the watch is up and running and looking good now. Without the laser, I doubt
I'd have bothered to try it (the hinges were originally pretty torn up, and I
made em a good deal worse with my intial attempt to fix them...) Now, It's hard
to see that it's been repaired, or even where I did any work on it. Like I
said, laser welders make some of the previously impossible jobs, almost
trivially easy...

Cheers

Peter

Peter W.. Rowe, wrote:
snip....

And a note to Paul, if indeed you spend a lot of time repairing antiques with
things like filed notches, well, my friend, you NEED to discover laser welders.
They fix that sort of thing with ridiculous ease, even with multicolored metals,
platinum, or very fragile pieces. The things are costly, yes. But if you've
got enough volume of work that will benefit from the technology, the machines
can quickly pay for themselves in increased productivity, and simply the ability
to do both superior work, and jobs which previously were not possible.
more snip...
Without the laser, I doubt
I'd have bothered to try it (the hinges were originally pretty torn up, and I
made em a good deal worse with my intial attempt to fix them...) Now, It's hard
to see that it's been repaired, or even where I did any work on it. Like I
said, laser welders make some of the previously impossible jobs, almost
trivially easy...

I neither own nor have access to a laser welder, and certainly can't
afford to buy one now that I've virtually retired. Several months ago I
purchased a PUK2 machine. Its less than a tenth of the price (and size)
of a laser but can produce similar results. Its a sort of combination of
a TIG and spot welder in miniatu it makes tiny spot welds on
stainless steel, titanium and any precious metal - giving very similar
results to a laser, but using a different technology. Its possible to
weld claw tips that hold opals or pearls with removing them, and can
also be used to repair blow holes in castings.
Just thought you might like to know...

--
Regards, Gary Wooding
(To reply by email, change feet to foot in my address)

Peter W.. Rowe, wrote:
On Sun, 26 Nov 2006 10:35:28 -0800, in rec.crafts.jewelry "Paul K. Dickman"
wrote:


As usual, Peter's reply is accurate, concise and helpful. But I feel I need
to add to the section on file notching.

Pauls comment on notching is right on, and bears a further comment. Remember,
when testing jewelry, that part of the idea is not only to establish the value
of the metal, but not to damage the value or physical integrity of the jewelry.
cutting into the item with a file is only needed if one suspects plated or gold
filled wares, and as I noted, often this can be determined simply visually,
without needing to file notches. And as Paul notes with karat gold jewelry,
some antique or otherwise rare items, even if made in gold filled or even plated
metal, can have significant value. Going wild with a file can do a lot of
damage to that value.

Sounds like the best option for me is to just get an electronic gold
tester (I don't know anything about jewelry). Thanks for the
explanations!

On Mon, 27 Nov 2006 23:04:51 -0800, in rec.crafts.jewelry "yawnmoth"
wrote:

Sounds like the best option for me is to just get an electronic gold
tester (I don't know anything about jewelry). Thanks for the
explanations!



considering the fact that these testers cost upwards of three hundred to five
hundred dollars or so, I'd suggest that unless you've got an ongoing substantial
use for the things, your best bet would be the simplest one. Take your items to
a local jewelry store and ask someone there, who hopefully DOES know something
about jewelry and might be able to tell you. Even if they charge you a small
amount for an acid test or something, to be sure, it's likely less money, and
less fuss, than testing only a few items yourself.

If it's more than a few items, or is an occasional ongoing need, then I'd
still suggest going with simple acids and a touchstone. you can get kits to do
this for under fifty bucks, and it's not really any more difficult than using
the testers (which is not totally simple either, and the testers have componants
(an electrolyte gel) that has a limited shelf life. The testers are great for a
busy environment where the test may be needed frequently, and time is important,
and people doing it may not be as comfortable testing with acids. But they're
simply rather costly. Acid testing, though it sounds ominous, actually is
pretty safe and simple to do, and is quite reliable and accurate. The kits
usually come with decent instructions (which will pretty much duplicate what
you've been told here, plus a bit about testing other metals, like silver.

But like I said, if you've only a few items, do it the easy way, and ask a local
jeweler rather than fussing with trying to figure it out yourself. Of course,
if you're curious about jewelry and want to learn, then it's a whole different
discussion... (grin)

Peter