TESTING WITH...GOLD & SILVER TESTERS 
A general article about testers for precious metals

To read an article about electronic testers, click here

To read all about chemical testers, click here

For a review of the latest electronic gold tester (the AGT1 GemOro AuRACLE), click here

Scroll down or click here to see how various electronic gold testers compare

There is a technical article about acid testers which includes:
What is the difference between the models?
What is each bottles for?
Hints and Tips, and Limitations
How to Use the Bottles
Safety Information

There is also a very good book on the subject.

To buy the testing sets click here
(or for refill bottles click here, or for accessories 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. Gold and silver are not magnetic. So if it's magnetic it can't be gold or silver. 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, because 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?
A. Yes. We've been manufacturing and selling the QUICKTEST testers since 1986 and the Troytest testers since 2008, 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, you do need to spend a few minutes practicing, 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, our acids do not require you to see the difference between green, brown and grey! Total colour-blindness is extremely rare and is associated with more serious eye conditions (if you think you are totally colour blind, see your optician).

Q. Will it test all colours of gold?
A. Yes

Q. Will it also test for silver
A. Yes

ELECTRONIC GOLD TESTERS

Low-cost testers that use an acid contact fluid or gel. Some have a row of lights to indicate commonly-used carats or a digital readout. For £95.00 you get to see readings for not gold, 10K, 14K and 18K (we have discontinued this one), for £149.00 you get nine lights, for 9, 10, 12, 14, 16, 18, 20, 22 and 24K - we sell this one (all are American and display 'K' for Karat rather than 'ct' for carat). The problem with these is that you never know if the machine is rounding a reading up or down. Other machines have a digital readout that displays the exact carat. The problem with these is that although it looks as if you are measuring to the nearest 1ct, it is nearly always incorrect, in practice it is no more accurate as the versions with the lights. Applying the acid is either from tiny bottles with droppers, or as an acid gel with a 'pen dispenser'. Typcially, you will file the item, 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'. After taking the reading you must meticulously clean away all the acid or it will dissovle the machine. You must always file the item first as these will not test through plating (they will test through very thin plating, but since you don't know if the item is plated, you have to file it first).

Low-cost testers that don't use an acid contact fluid or gel. We sell the AGT1, click here to see detailed review. Summary: it's fast, it does not use any acid liquid or gel whatsoever, it has a row of 32 LED lights enabling very accurate readings on 9ct to 14ct, adequate readings on 14ct to 18ct, not so accurate on 18ct to 24ct. But far better than the testers (above) that have a handful of lights. £399.00.

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. We do not sell these.

Table-top XRF (X-Ray Fluorescence Analysis technology). The larger machines weigh 20Kg, connect to a computer (not supplied), and each test takes a minute or two. They say they are easy to use (I've never used one). They cost about £8,000.00. Advantages: it's more accurate than acids and it's non-destructive. Disadvantages: they are large and heavy, relatively slow to use, will not test through heavy plating, and require careful setting up and regular maintenance. We do not sell these.

Handheld XRF machines cost £12,000.00 to £15,000.00. I have spent a few hours playing with one of these, they are impressive: within a few seconds a breakdown of the chemical composition appears on the screen. They are easy to use and require no setting up other than selecting the correct profile on the touch-screen. Disadvantages: they can only test through very thin plating, in other words you still have to file the item; although they do not involve acid, they use x-rays (highly dangerous if pointed at someone). We do not sell these.

There is also the Melt-and-Assay (Fire Assay) method of testing (not electronic). Melt the item (or part of it - if only a fraction of a gram). The service costs (if we get it done for you) £95.00 and takes two to three weeks.