Testing of gold
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. 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.
Simple tests
Before you start, LOOK at the item. 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; 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.
• First, 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.
• Second, hardness/malleability. Precious metals are soft; large
thin gold items (especially if made of high-carat gold) bend easily
in and out of shape. 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 of 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.
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 tells you whether the item is gold or silver, as well as 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, which is 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 commonly
asked questions about these acid testers.
Q. Do they work?
A. Yes. QUICKTEST-3 has been manufactured and sold to the trade
since 1986. Mankind has been using the acid test for hundreds of
years, and it has even entered the English language as a signal of
ultimate proof, "The acid test is…"
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 as on 9ct
(usually) and on 14ct / 15ct (sometimes) it leaves a dull stain.
This can be polished off with a soft cloth and a gold cleaner.
Q. Is it easy to
use?
A. You need to handle acids with great care, but the instructions
are very clear.
Q. I am
colour-blind, how will I see the colour-change of the acid?
A. There are special instructions included with the Quicktest-3
tester explaining what the "colour change" looks like to
colour-blind users.
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 method of testing, especially for platinum,
Q. So what are the
different bottles for?
In the QUICKTEST-3 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 to 24ct.
The 4-bottle TROYTEST has the same first three bottles and an
additional one to distinguish 18ct white gold from Palladium - if it
is neither of these then it's probably platinum, but that isn't
certain as it's a 'negative test'.
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.
The acid testers and
electronic testers require a very steady hand and good close-up
eyesight, so if either is a problem consider getting the metals
professionally tested. |
