And do I have the correct on making this karat gold
determination?
From your description, that you’re upset because the gold turned
color under the acid, then I’d have to say probably not, depending on
the type of kit you have, and how you used it. Acid testing is not
always as simple as it seems, and the acids commonly sold (the
premixed ones, marked for karat), can be confusing to use without
some practice.
14k gold, exposed simply to plain nitric acid, WILL discolor.
Depending on the mix of acid, (the premixed ones generally have some
mix of both nitric and hydrochloric) the exact reaction to a given
karat can be variable depending on the exact alloy. The best way to
be sure is with the type of kit that also includes test needles. You
need to put a streak of a known, same color, gold on a dark tile or
test stone, and a streak of similar thickness of the unknown gold
next to it. Add the test acid. What you’re looking for generally
is NOT whether it turns color, but rather whether it is affected by
the acid at a different speed than is the known sample. It is
generally supposed to be affected to some degree, which may be a
color change, or actually dissolving, or you wouldn’t be able to
judge the relative speed of action.
If in doubt about the acid, purchase plain, concentrated, nitric
acid (USE WITH CARE). A drop of this on most 14K yellow golds will
slowly give you a dark spot on the metal. On a test stone, it also
slowly discolors it. If in doubt, spread the drop of acid over about
half the length of the streak, then add a single grain of table salt
to one end of the puddle, stroking the acid there back and forth
across the ends of the two streaks with the glass acid bottle
applicator. As the salt dissolves and dissipates in the acid, it
greatly speeds up the effect on the gold (you can use this with
higher karats too), so you can then more easily judge which streak is
affected more quickly. Comparing the reaction to acid of the unknown
gold versus the known samples of the same color alloy, is capable,
with practice, of measuring within about a half karat or so, but
that’s with practice.
the above method, by the way, of using just nitric, with some salt
if needed, has the advantage that the premixed acids have a distinct
shelf life. if the kit has been on the shelf for a while, it’s
sometimes hard to be sure the acids are still as potent as they are
supposed to be. Plain nitric has a longer shelf life like this.
Experienced testers will use, instead of salt, a second bottle of
hydrochloric, as the combination of the two lets you also
effectively test platinum group metals, as well as being more
effective with high karat golds than the nitric/salt combo. But the
latter is cheaper, less acid to store and keep track of which bottle
is which, and for karats up to about 18K, just as accurate in my
experience.
And even with golds of the same karat, slight differences in color
(a slightly more rose, or slightly more “green” gold, for example) ,
will make the gold react differently. And so can differences in the
alloy such as differing levels of deoxidizers or other trace additions
used to improve casting quality, which may make no visible difference
in color.
For this reason, if you find that you are not confident in the karat
of gold of an unknown alloy such as this case, then you really need to
submit a sample to a qualified refiner who can offer a proper assay,
which will be FAR more accurate than a simple acid test. These
generally cost anywhere from 25 to 50 dollars to run. But only then
will you really know what the alloy is. Testing kits are OK for
checks where you don’t need exact accuracy, and are best when
you’re pretty sure of the type of alloy involved. But modern casting
alloys can be tricky sometimes. Don’t be too quick to jump to
conclusions. Casting companies, like jewelers, don’t stay in
business very long if they cheat their customers. So before being sure
of this problem, get the piece properly assayed. And talk to the
casters as well about your misgivings. People are all too human,
and even the most honest and conciencious caster may, on occasion,
have some sort of accidental mix up occur. Shouldn’t happen, but
every now and then, can happen, without it being intentional or
something that would be repeated.
And consider telling us, here on orchid, the name of the caster. if
you’re unsure of whether you should do this in public, register on
orchid with a new user name, so we won’t know it’s the person with the
problem, and then simply ask for Orchidians to tell you of their past
experiences with this caster. If everyone raves about how great they
are, then you can feel better that any mistake was proably a fluke.
Peter Rowe