This is my article about electronic gold testers, as published in this issue (Nov-Dec 2013) of Antiques Info magazine (available in Smiths).
You can see a longer version of this article on our website.
In the last issue, I told you about testing gold (and silver and platinum) with acid: the acid test, the ultimate proof.
There are also a great many electronic testers on the market, but are they as accurate as the traditional acid test? I shall tell you the answer at the end of this article.
Firstly, be very cautious when you read the sales hype and when you look at product photographs. The photographs show a ‘pen probe’ suggesting that you simply touch the probe onto the metal and it gives a reading. Not so! I shall explain.
That probe, it’s not just a probe. It connects to a metal plate and a box of electronics (though the electronics can be built into the probe or the plate); the test-item must be filed (there is no electronic tester that can test through plating!); a contact fluid is used to complete the electrical circuit; the reading is displayed on a meter.
The simplest electronic testers (e.g. the Mizar brand) cost from £100.00 (to test 9ct o 18ct) to £150.00 (to tests 9ct to 24ct). The advantage of these is that they are ‘automatic’, you don’t have to calibrate them (check them against a known sample). The disadvantage is that because you can’t calibrate them, they are not always accurate. Another disadvantage is that they use a contact solution made of acid. The advantage is the low price.
Moving up-market, the Auracle brand costs from £300.00 to £500.00 and tests from 8ct to 24ct, plus platinum. The contact fluid is a salt solution. Their top model connects to a mobile phone, you still need the metal plate and box of electronics, but it’s smaller than the standard model because the meter and buttons become part of your phone. The phone app is, as you would expect, free. But you still have to lay out £500.00 for the tester.
All of the above are sold by us (QUICKTEST) and because this is our specialist subject we have carried out many thousands of tests, and published test-results and reviews on www.quicktest.co.uk.
Many people turn pale and quiver when it is suggested that they spend between £100.00 and £500.00 on an electronic gold tester, they point out that chemical testers (which we manufacture) start at £40.00. Please allow me to put this into perspective by describing two more electronic testers, which we do not sell.
XRF (X-ray Fluorescence) displays the item’s chemical composition on a screen. So whereas the simple electronic testers described above might tell you, “It’s about 9ct, maybe a bit more”, an XRF tester might display, “38.1% gold, 54.5% copper, 4.2% silver, 3.1% zinc”.
Scrap dealers and antiques dealers tend to go for basic XRF models, they look like an oversized barcode scanner and you can now get them for as little as £12,000.00. The models used in laboratories are the size of a microwave oven, from £30,000.00 to £50,000.00 (one buyer at a laboratory assured me that you have to spend £50,000.00 to get a decent one).
So now for the big questions: how do the various testers compare?
As regards safety, the cheapest (£100.00 to £200.00) use an acid contact solution, it is acide, treat it with care; the £300.00 to £500.00 testers use a harmless salt solution. XRF testers use x-rays, the ‘scanner’ type have no safety featuresl, you have to remember to keep your fingers away from the emitter as you pull the trigger or you will blast them with dangerous x-rays.
As regards maintenance costs, replacing the contact fluid (or probe) of a basic testers costs £15.00 to £30.00 (enough for hundreds of tests). The tube of an XRF tester lasts three to five years costs about £6,500.00 to replace.
As regards accuracy, the cheapest (up to £200.00) tend to have a light for each ‘standard’ carat, e.g. 9ct / 14ct / 18ct. You will never know if the machine is rounding a reading up or down – not very accurate. The better makes (e.g. the Auracle) have a row of 30 lights so it’s easier to judge just where, between ‘standard’ carats, the reading falls; the top Auracle model) has an LCD display to show you the exact carat.
Finally, how easy is it to buy these testers? We manufacture the chemical testers and import the Auracle electronic tester, see www.quicktest.co.uk.