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| TESTING
WITH...GOLD & SILVER TESTERS There
is also a technical
article about testers which includes: To
buy the testing sets click
here ALCHEMY AND THE TESTING OF GOLD 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, using an electronic portable low-cost machine non-destructive machine. Alas, even today, with the latest technology, this just isn't possible. 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. Wall charts explaining hallmarks are shown (by law) wherever precious metals are bought or sold, familiarize 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 testers are manufactured by QUICKTEST, and are branded QUICKTEST and TROYTEST. They comprise small bottles of acid in a strong wooden box, the QUICKTEST-3 tests for gold (all carats) and silver, the TROYTEST models have extra bottles for distinguishing white gold from steel and platinum, or for testing hig-zinc / 8ct gold. 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 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? Q. Do I put
the acid on the filings that have been taken off with the needle file? Q. Do I HAVE
to file the item? Q. Does the
acid cause any damage? Q. Is it easy
to use? Q. I am colour-blind,
how will I see the colour-change of the acid? Q. Will it test
all colours of gold? Q. Will it also
test for silver Q. Will it test
platinum?
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? Q. How do you
know whether to test just the surface or test it for plating? Q. Does it cause
any damage? Q. Will it test
all colours of gold? Q. Will it also
test for silver? Q. Will it test
platinum? Q. Is it as
accurate as the traditional acid test?
OTHER TESTERS 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 quantities of scrap. Disadvantages: you need to destroy a sample (albeit a fraction of a gram), costs £45.00 for a test (we can get this done for you) and you will have to wait 2 to 3 weeks for the result. 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 more accurate than acids and it's non-destructive. Disadvantages: it's large, heavy, slow, and expensive. However...both the sizes of the machines and the prices are coming down, handheld models are now coming onto the market for as little as £10,000.00). These are not, of course, for the secondhand dealer who sometimes finds bits of jewellery, these are for serious scrap merchants who buy several Kilo. of gold per month. I am now investigating the possibility of selling these, watch this website! 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 £35,000.00. There are some variations. In the 'chat'
emails of the Gemmological Association of Great Britain, someone asked
if the same equipment can be used for gemstones, and also about the problem
of overlapping values. The response (from "Bear") discusses
the relative merits of XRF and WDX and indicates that these technologies
are not for the feint-hearted (and these 'testers' cost upwards of £35,000):"From
what I've gathered, the overlap problem is something akin to the grating
problem with spectrometers. In the case of XRF, as the X-ray source excites
the sample, you will have a signature overlap based on how atoms are stacked.
The energy released from the test sample may have a similar emission based
on it's electron configuration. But yes, you can use just one instrument
to get all your readings. These problems have been overcome by using a
multi-channel type system that eliminates the overlap...you just have
to pay more for it. There is another method called WDX that works in similar
fashion to XRF but (I believe) it manipulates the emission and re-interprets
in waves" MY RECOMMENDATIONS FOR ACCURACY AND COST: choose the acid tester. FOR EASE OF USE: both the acid testers and the electronic testers require a very steady hand and good close-up 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; the electronic gold tester has 7 pages of instructions including 10 Do's and Don'ts and a troubleshooting guide.
COST (including VAT) TESTING SETS Quicktest 3 £40.00 (for all gold and silver); Troytest (Troytest 4 £50.00 for gold, silver, platinum; Troytest 5 £60.00 for gold including 8ct, silver, platinum). ELECTRONIC TESTER M24 £139.00. REFILLS For the acid-only testers £8.50 per bottle (£10.00 for the Clear Fluid); for the electronic testers £22.50 each (includes refills for the now-discontinued ET18 model). The Gold & Silver Buyer's Handbook by Raffi Katz, £12.50 (new edition March or April 2010)
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QUICKTEST, Watford, WD18 8PH, Tel. 01923 220206, email info(at)quicktest.co.uk |
