On Thu, 09 Apr 2009 19:25:09 -0700, in rec.crafts.jewelry Muso
wrote:


Hello Peter,

and thank you for keeping such a high signal-to-noise ratio with this
group. Well, as you have pointed out, zinc is an "irony" metal, and
although jewelers are known for working precious metals, they also are
no strangers to iron. For example, jeweler's anvils are best made of
steel, although iron and zinc can be considered as substitutes,

Iron makes a good anvil. Zinc, however, makes cheap trinkets in die cast molds,
not quality tools, especially not ones needing some strength. There ARE, of
course, some more complex zinc based alloys that have better properties, but
pennies are not such an alloy. Costume jewelry is sometimes made of plated
"white metal", which may often be a zinc based alloy for the cheaper stuff, or a
tin based one (pewter) for better quality.

My reference to irony was not to imply any great similarity between zinc and
iron. There isn't, at least not in practical terms.

And more to the point, you've not yet explained why anyone would wish to melt
pennies for the zinc in them. As Abrasha pointed out, it's a poor way of
getting zinc, since what you'd get would be an indeterminate mix of zinc and
copper, plus the various impurities introduced from the higher than normal
melting temperature needed to break down the penny, plus the higher than usual
percentage of absorbed gasses, oxides, etc, due to torch melting such a small
amount of the stuff.

The notion that pennies are a good source of tiny zinc ingots is silly. Buy a
bit of zinc, and use what you wish. It need not be in ingots. You can get it
granulated, or if in more solid stock form, clip off what you need. Simple, and
can give you a purity you'd actually wish to use in, for example, alloying.
Pennies are a poor way to add zinc to an alloy anyway, since at least in terms
of jewelry alloys, you're usually adding it to much higher melting point metals.
The best way to do that is with an intermediate "master" alloy, usually
something like an alloy of copper and zinc. You can get quite pure brass with a
known ratio of zinc to copper, and this is a good way to introduce additional
zinc into an alloy. Yes, you must also take the copper in the brass into
consideration, but that's just a bit of simple math. Even if you need to spend
a few more moments getting the needed ingredients together to alloy what you
wish, your end results will be better. Zinc cored pennies are a poor way to
get a good alloy.

especially among those of us who are keen on making our own tools.
Jeweler's vices and jeweler's lathes also come to mind here, as well
as a long list of other tools which are specifically made for the
jeweler.

None of which normally are made of zinc. Well, maybe some things like
non-marring inserts for vise jaws, or the like. But normally, even then, zinc
isn't the common choice of metal to use.


Yes, Peter, in fact, a person can make more than one-hundred and
eighty pennys from a pound of zinc. So far, though, I have not found
anyone except the government who makes zink pieces in penny sizes.

You haven't yet said just why you need them. And why this impure and imprecise
method is acceptable...

And, of course, with pennys, there is no paying for shipping, waiting
for shipping, and so on.

No, but for your penny, you've paid far more than the value of the zinc. Do it
right. Find any decent metals supplier or lab chemicals supplier or whatever.
Buy yourself a pound of zinc granules, or whatever other form you find easy to
use. Be set for life.

This gives the government ingots the edge.
You are correct about the reason why the government began making zinc
pennys. However, it was evidently just recently that the government
outlawed the melting of zinc pennys for the same reason. This, in
itself, indicates the competitive nature of the government's coins as
a casting medium.


Either that, or they're trying to be benevolant, protecting people from the
temptation of using their pennies for a purpose for which they're not well
suited, thus protectiong consumers from potentially flawed and inferior
products, and helping to maintain the high quality of U.S. made products by
making it more likely that the proper materials are used.

Face it. coins are simply not intended, nor especially good for, casting
purposes. The main exception to that might be using pure gold bullion coins
like Canadian Maple leafs, or the like, as the source for gold with which to
alloy your jewelry alloys. But even that is more expensive than buying pure
gold casting grain.

The whole topic, though, reminds me of a story I heard years ago, from a refiner
and metalurgist I was using then (now long retired). He'd been hired to help a
major jewelry manufacturer try to track down why they were having occasional
problems with their merchandise ending up under karat. It was driving them
nuts. They were buying high quality new alloy from reputable suppliers. Most
of their castings were fine. But occasionally a batch would come out just
enough under karat it would have to be totally scrapped. Eventually it was
traced to the casting department. The normal casting guy was doing things
right. But on his days off, two other fellows would fill in. One was this old
timer who'd been there forever, and pretty much knew it all, or so his
reputation went. My friend happened to be there watching the casting process
while he was doing a batch. The gold went into the melting furnace. Melted
just fine. Just before pouring, the old fellow reached into his pocket, pulled
out a penny, and tossed it in "for luck". When questioned, he said he felt that
the little extra bit of copper and zinc in the penny led to less porosity or
something (maybe even true with the old traditonal non-deoxidized alloys he'd
learned with way back). Problem solved. It had never occurred to him, due to
the size of the melt (several ounces at least) that his addition to an otherwise
very precise alloy was enough to lower the karat below legal standards. Now, I
heard this story second hand from my refiner, and I have no idea if it was
actually true, or just a nice illutration of how product quality can be affected
by things you'd never expect to look for. But it does nicely illustrate one
reason why pennies might not be the best thing to add to your gold alloy...

Peter