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Metal testing


#1

Hi Gang, Well here’s another “restarting” question. I finally got an
acid testing set-- something I never had back in the 70s & 80s. Now I
can test for 10, 14, & 18 KG plus Silver. Yay!

Here’s the question-- my Aunt sent me a large roll of wire which we
sort of think is some kind of binding wire my uncle had on hand.
However, my Aunt said she found it in one of his hidey holes where
he hid precious things-- such as gold, coins, silver, etc. (he has
since passed on-- rest his soul). The wire was both non-magnetic &
un-tarnished–.

Just in case it really might be a precious metal, I tested for
silver and eliminated that possibility. Then I used the 18k gold
testing acid and a scratch stone. The scratch made with the wire
remained untouched. Hmmm white gold, I thought-- my heart beating
faster. My husband kept saying it was probably aluminum. So I took a
piece of known aluminum and scratched the stone-- same thing. The
line looked a lot like the wire scratch line – and the acid did not
touch it. Awww…

Next day, my husband brought a friend’s ring home that needed a new
stone. He said the guy thought it was steel but didn’t know. It is
white metal, fairly heavy and thick-- and non magnetic. There had
been a stone in it but now only a depression remained. I assumed it
was costume-- as the stone hole did not go all the way through. My
logic here is simply that a good stone would require an open back–
and who would put a poor stone in a platinum, paladium setting?

I was able to gypsy set a stone into this band after expanding the
opening and drilling the hole all the way through. It was a bit
tough, but not so hard it could not be drilled. I’m thinking
aluminum would have bee very light & soft-- right? In any case, I was
able to push the metal around the stone, and with some effort, buff
it up.

And oh yes, this ring withstood the scratch test for 18kg – just
like the wire did, and tested out for non-silver.

Both of these things are a mystery to me. Does aluminum withstand
the acid test for gold? Any suggestions on how these things can be
identified? What sort of clues, process of elimination… etc. ?

Still hoping that roll of wire is really platinum–!!:slight_smile:

Thanks & Cheers,
Carol / Austin


#2

With the wire, have you tried apply a flame to the end? I would try
that first. If it melts easily it’s not platinum or palladium. They
have a very high melting point and will glow “white hot” before
melting. You won’t in fact be able to melt it unless you are using an
oxygen acetylene mix or hydrogen oxygen (micro welder) mix.If it
glows bright orange and then “burns” it’ll be steel or iron. If it
melts before you see it glow then it’s either aluminium, tin or zinc.
How heavy does it feel? Platinum and palladium are very "massive"
metals and it should “feel” much heavier than anything you are used
to. If it does feel unusually heavy doesn’t melt easily, or only at
very high temperatures without “burning”, is very malleable and is
fine (like binding wire) I would guess that it’s oragin would be from
the thermostatics industry. Some ceramic thermostats which measure
very temperatures use a very fine metal core from metals within the
platinum group.

As for the ring, the same goes for it’s weight. The fact that the
stones setting was not drilled all the ways thru does not necessarily
mean it was a rubbish stone and there for a “Fashion” item: a diamond
for example does not “need” and open backed setting light or
refracted light that you “see” at the front of the stone is light
that entered the stone from the top bounced back at you from within
the stone (if it’s well cut). Does the ring feel “heavy”? If you find
that difficult to judge then test it’s specific gravity (like
Archimedes).

There is an article I think on plaladium testing on ganoksin, but I
am not sure if your acid testing kit has the correct chemicals. If
the “large roll” shows signs that it could be something precious
then it’ll be worth forking out some cash for proper investigation.


#3

Ther are several physical tests you can do to distinguish between
aluminium and precious metals. Aluminium will dissolve in most acids
but is particulary susceptible to dissolving in sodium hydroxide-
the stuff that is sold for drain cleaning as caustic soda. White gold
and platinum metals will not be touched by that. Another good test is
to measure its density. Weigh the piece (or a piece) and then
calculate its volume by either measuring the length and diameter in
cm, dividing the diameter by 2, multiply that by itself and then
multiplying by pi (3.1412). multiply this area in sq cm by the length
in cm and divide by the weight in grams. This will give you the
density in g/cm2. gold has a density of 19, platinum about the same
and aluminium is about 3. Displacement can be used to measure volume-
drop the piece in a beaker that is full to the brim and standing in a
larger vessel. Measure the volume of the displaced water or weigh the
displaced water and call it 1g/cm2 to calculate volume. divide this
by the weight of the piece used to determine density.

You can heat a small piece of the metal along with a small piece of
aluminium and see if they melt at the same time. if they dont, repeat
the melting test with a piece of white gold or silver (similar m.p.)
look at the state of oxidation on the metal- if it is untarnished and
hasnt melted with the gold/silver then it could be platinum. If it is
tarnished a greeny grey it is probably nickel silver, which is very
resilient to acids and will have a density of about 7.

have fun!
Nick


#4

wite gold (any karat) contains nickel unless it is clearly stated as
palladium/Pt based…the scratch test is not an accurate assay tool
for what you are trying to find out…In all likelihood the
untarnished wire you have is nickel.Simply weigh it…and look in any
of your metal suppliers catalogs that give the weight of x wire per
foot, measure a foot of what you have and compare the results to
sterling, platinum and nickel…there are a number of anti-tarnish
craft wires on the market that are nickel based…Aluminum is a rather
dull silver colour and dead soft. there are a number of other simple
tests you can do to determine the wire’s content (if you want to know
more simple tests email me off list or look on a science experiments
site targeting kid’s as the audience) but most probably it is not
platinum, or white gold… Look at the spool too,you may find some
clues there as to the manufacturer…


#5

Hi Nick, thanks for the great info! It is shiny, and therefore likely
not aluminum-- per several e-mails. I may do the heat test next…
Specific gravity sounds weighty…:wink:

Cheers!
Carol S. Stall
Austin, TX
PS: Nick, in which part of the UK do you live?


#6
With the wire, have you tried apply a flame to the end? 

If it is bright and shiny and refuses to melt despite your efforts,
it could be nichrome-- nickel-chromium-- wire. This is used in high
temp applications like kilns, but it very pretty before high heat
turns it gray. it is, or used to be, pretty expensive. My father
used to make jewelry for my mother out of leftover bits from the
shipyard where he worked (50’s). I guess she didn’t have any nickel
sensitivity!

Noel


#7

There are all sorts of (offhand) tests for metal - heating,
magnetism, smell, bending, feel, experience - many have been posted
here.

For acid tests, though:

Dilute nitric acid is for silver, brasses and bronzes, including
nickel silver. Adding a drop of acid to fine silver will foam snowy
white, sterling will foam greyish white, and brass or bronze will
foam green. No foam means it’s not one of those things, obviously.

Aqua Regia is the stuff you get in test kits, and is used for gold
and platinum as directed - I won’t rehash that.

Hydrochloric acid is your other tool - buy it in the hardware store
as concrete etch or cleaner, or muriatic acid. It will affect most
of the other metals you’ll find - iron and steel, tin, lead, zinc,
aluminum. Depending on the metal, it may not actually foam, but just
leave a stain. That’s enough to know there was a reaction - if you
put HCL on platinum it will leave it unaffected.

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