In the middle ages alchemists made it
their life’s aim to find 'The Philosopher's Stone', a substance
that would turn ‘base’ metals into the ‘noble’ metal of gold.
They were unsuccessful. Even today, with the latest
technology, it just isn't possible. Current-day jewellers
have a similar ambition. To find a method of testing precious
metals without the use of acids. Alas, even today, with the
latest technology, that isn't possible either It is therefore
the traditional ‘acid test’ that is the universal test for
precious metals, either on its own or with an electronic tester
(more about those later).
SIMPLE TESTS
Before you start, LOOK at the item.
And if you can’t see clearly, buy a good quality magnifier,
it will be the best ‘tester’ you ever own. All modern gold,
silver and platinum items made in the U.K. or imported into
the U.K. should be hallmarked (despite recent complications
with E.U. law…but that’s another story).
Wall charts explaining hallmarks are
shown (by law) wherever precious metals are bought or sold, familiarise yourself with these marks, it’s as important
as being familiar with coins. Forged hallmarks (as with
forged coins) exist but are rare, possibly because the authorities
go to lengths to track down forgers, with a maximum penalty
of seven years in jail.
No hallmark? Then start testing! The
first two tests do not require acids.
Firstly, a magnet. Precious metals are
not magnetic. So if it's magnetic it can't be gold (or silver or platinum). Of course, if it's NOT magnetic it doesn't prove anything.
Secondly, hardness / malleability .
Precious metals are soft, large thin gold items (especially
if made of high-carat gold) bend easily in and out of shape.
Also, before testing the item you will have to file the
surface with a fine steel file (otherwise you will merely
test the surface plating). This is a good test in itself,
you will soon see how easy it is to file gold or silver
whereas the steel file will 'bounce off' an item made steel
- no need to test any further.
THE ACID TEST
You've tried all of the above, you may
have your suspicions, but now you need absolute proof: the
acid test.
The most popular tester is manufactured by QUICKTEST
and is called the "QUICKTEST-3". It comprises
three small bottles of acid in a strong wooden box and tests
for both gold and silver.
This is what you do.
Choose a place on the item that is not
normally seen and file the surface (a fine needle file is
included). Do this firmly but only over a very small area.
This is to get past any plating - if the item is gold plated
then the surface IS gold and will test as such. Now put
a tiny spot of acid on the filed area of the item (read the instructions before applying the acid!). The acid will
change colour, and that tells you whether the item is gold
or silver and also the purity.
The QUICKTEST-3 acids are designed to
test to the nearest purity (carat) commonly used in jewellery,
9ct, 14ct (or 15ct), 18ct, 22ct. though with practice results
to within 5% can be achieved, useful for scrap. The same
tester will test for silver, giving a very clear reading
on Sterling (.925) silver and a less clear reading on 'low-grade'
(.800) silver.
Here are common questions I am asked
about these acid testers.
Q. Do they work?
A. Yes. We've been manufacturing
and selling the QUICKTEST-3 to the trade since 1986, and in January 2008 we bought TROYTEST and now manufacture the TROYTEST testers too; and mankind
has been using the acid test for hundreds of years, it has
even entered the English language, we say (referring to ultimate
proof), "The acid test is…" And so yes: these testers work.
Q. Do I put the acid on the filings that
have been taken off with the needle file?
A. No, you put the acid on the actual
item
Q. Do I HAVE to file the item?
A. Yes. There is no way of knowing
if the item is thickly plated unless you file the surface
to test underneath, so if you can't file it you can't test
it.
Q. Does the acid cause any damage?
A. You must file it in a place where
it won't show. If you can't file it you can't test it. On 9ct (usually) and on 14ct
/ 15ct (sometimes) it leaves a dull stain. This can be polished
off with a soft cloth (and perhaps
your favourite gold cleaner).
Q. Is it easy to use?
A. You need to handle acids with great care, but the instructions are very clear,
it's not difficult.
Q. I am colour-blind, how will I see the
colour-change of the acid?
A. I'm red-green colour-blind and
I have included special instructions explaining what the "colour
change" looks like to me. Total colour-blindness is extremely
rare.
Q. Will it test all colours of gold?
A. Yes, the readings are the same
for yellow, red and white gold.
Q. Will it also test for silver
A. Yes
Q. What about platinum?
A. The TROYTEST tester
has an extra bottle and a slightly different testing method of testing, especially for platinum, HOWEVER, unlike the other tests the test for platinum is is a 'negative' test,
if there is no colour-change then the metal is probably
platinum.
Q. So what are the different bottles for?
The silver (amber fluid) bottle tests for silver; the 9ct (white fluid) bottles tests for non-gold or 9ct gold; the 18ct (blue fluid) tests for 14ct to24ct. Those are the three bottlesof the three bottles of the QUICKTEST-3 and also the first three bottles of the TROYTEST.
The 4-bottle TROYTEST has a fourth bottle, the Green Fluid, to distinguish 18ct white gold from Palladiumi - if it is neither of these then it's probably platinum...but that isn't certain, it's a 'negative test'. There's also a fairly complicated method of using this bottle to test for 14ct yellow gold.
The 5-bottle TROYTEST has a fifth bottle, the Clear Fluid, to test for 8ct and also an unusual alloy of gold and zinc used to make a 9ct gold that can indicate NOT GOLD on the standard 9ct test.
ELECTRONIC GOLD TESTERS
The method is as follows.
Clean a small area of the item with
the eraser (a simple pencil-rubber), fill the 'well' (a
hollow in the machine) with 'activator fluid' (acid), clip
part of the item to the crocodile clip, then dip another
part of the item very carefully into the fluid without it touching the sides of the 'well'. Lights indicate
the purity (carat).
Questions concerning electronic
testers.
Q. Are they easy to use?
A. The basic model (tests for 9ct,
14ct or 18ct) is quite straightforward, the advanced model
is complicated. With both models, if you suspect the item
might be heavily gold plated you must varnish a small area
of the item, file through the varnish (and into the item),
put the acid over the varnish / filed area, test it, clean
everything up thoroughly, test it again on a non-varnished
/ non-filed area, then compare the two readings, a laborious
process.
Q. How do you know whether to test just
the surface or test it for plating?
A. You don't. That's why you're testing it.
Q. Does it cause any damage?
A. You must file it in a place where
it won't show. If you can't file it you can't test it. The
activator fluid is acid and will stain low-carat gold just
the same as the traditional acid test, you need to polish
the stain off with a cloth.
Q. Will it test all colours of gold?
A. The basic model: only yellow
gold. The advanced model: yellow or white gold.
Q. Will it also test for silver?
A. No.
Q. What about platinum?
A. As with the traditional acid
test, there is a 'negative' test: if the tester indicates
22ct or higher then the metal might be platinum.
Q. Is it as accurate as the traditional
acid test?
A. With the basic tester the readings
indicate 9ct, 14ct, 18ct, you have no way of knowing if it's
in between. The advanced tester indicates 9ct, 10ct, 12ct,
14ct, 16ct, 18ct, 20ct, 22ct, 24ct. How ACCURATE (true)
these readings are I do not know
OTHER TESTERS
x-Ray Fluorescence Analysis technology. It weighs 20Kg, connects to a computer (not supplied), each test takes a minute or two, they say it's easy to use (I've never seen one, I don't sell these). Advantages: it's slightly more accurate than acids (3%), it's non-destructive. Disadvantages: it's large, heavy, slow, and costs £5000.00.
Melt-and-Assay (Fire Assay): remove a sample of the item (a tiny slither), melt and chemically assay it. Advantage: very accurate, good for large quantitiesof scrap. Disadvantages: you need to destroy a sample (albeit a fraction of a gram), costs £45.00 and takes 2 to 3 weeks (if you want us to get it done for you).
ICP (Inductively-coupled plasma mass spectrometry): requires high-vacuum system, high energy electron beam and an X-ray detector. I don't really know anything about this method except that the equipment costs about £30,000.00.
MY RECOMMENDATIONS
FOR ACCURACY AND COST: choose the acid
tester.
FOR EASE OF USE: both the acid testers and electronic testers
require a very steady hand and reasonable eyesight, don't
even THINK of buying one otherwise! I often glance quickly
at instruction manuals to see if an item is likely to be easy
or complicated to use: the 'Quicktest-3' has a two-page manual;
for the basic electronic gold tester, 4 pages including 14
Do's and Don'ts; for the advanced model, 7 pages including
10 Do's and Don'ts and a troubleshooting guide.
COST
ACID TESTERS.'Quicktest-3 £37.5.0 (for
all gold and silver); Troytest-4 £49.00 (gold, silver,
platinum); Troytest-5 (gold including 8ct, silver, platinum) £59.00.
ELECTRONIC TESTERS: the basic model ET18 £85.00, the advanced model M24 £129.00. Also available:
