Re: Pipe tamper

"Peter W.. Rowe," <rec.crafts.jewelry@xxxxxxxxxxxxx> wrote in message
news:ept5821kv4d1fnd5met1t8tu7r8b85dkj4@xxxxxxxxxx
On Sun, 04 Jun 2006 08:06:19 -0700, in rec.crafts.jewelry "Norm Dresner"
<ndrez@xxxxxxx> wrote:

On Sun, 04 Jun 2006 08:06:19 -0700, in rec.crafts.jewelry "Norm Dresner"
<ndrez@xxxxxxx> wrote:

"Abrasha" <abrasha@xxxxxxxxxxx> wrote in message
news:vs4482lab7ek0jqq24nf6ah80jicq2gfps@xxxxxxxxxx
Robertfl wrote:
I am looking for someone to make me a sterling pipe tamper. If you are
intrestet please comtack me via email.
Robert


Are you sure you want to have one in sterling silver. Silver just so
happens to
be the best conductor of heat on the planet.


Actually, Gold happens to be a slightly better conductor of both electricity
and heat than Silver but economic considerations limit it's applicability to
really high-end systems. For technical explanation, start at
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html

Norm

Norm,

Telling an experienced gold and silversmith he or she is wrong about the heat
conductivity of a precious metal is something to be done with caution and fact
checking (grin)

We're, after all, the ones who experience it's effects directly, in burned
fingers when hand holding a silver wire for annealing or melting an end, but can
get away with it in gold, or when soldering, where silver pretty much insists
on being heated overall, or you'll never get the joint hot enough for solder to
flow, while with gold, well, it's not as critical.

And your own data link backs up this experience. The page you link to itself
has a chart link at the bottom, at
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thrcn.html#c1 which shows
silver at the top, and doesn't show gold at all. (OK, not so useful, but bear
with me). It shows silver's thermal conductivity in W/m K at 406.0. At the
bottom of that chart, there's another link,
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/thrcn2.html#c1 to another
chart, this one in periodic table format. It also shows silver's thermal
conductivity, this time at 300K, in W/cm K, at 4.29. right below it is the
thermal conductivity listed for gold, at 3.17.

That places gold's thermal conductivity below both silver, and copper (4.01.)
Again, this is data that any experienced jeweler will not know in terms of
measurements and data, but will understand fully, just by experience. Silver
is a significantly better conductor of heat than is copper, and a much better
one than is gold. Mind you, it's still a very good thermal conductor at third
in line, with aluminum a somewhat distant fourth place.

The same ordering exists with electrical conductivity, as listed here: (again
found through links in the page you directed us to:
http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/elecon.html#c1
Silver is the best conductor, copper is second, gold is third, and aluminum is
fourth.

Where the orders are mixed up, of course, is in chemical reactivity among these
metals. Gold is much less reactive than silver or copper. This is the reason
why it is used for electrical contact coatings and fine wires in tiny circuits.
Gold's greater ductility also means these exceedingly tiny wires, as used in
integrated circuit internal connections, will be stronger, less easily broken
during assembly or by vibration in use. Silver and copper, though better
conductors, are prone to oxidation and formation of sulphides, which we jewelers
know as tarnish. These surface films then are insulators or at least, damaging
to the conductivity of a connection. The freedom from oxidation is the big
reason why silver is not used more, where we now use gold, in electrical
contacts (which often are only gold over a more conductive copper conductor) And
you will find, when you've got devices, like certain switches, that must
withstand high current flows or arcing (when mercury won't work, since the
liquid metal, though not a great conductor, is self repairing from arc
damage...) , that sometimes the manufacturers will still use silver as the
conductor.

cheers (and thanks for the good data links. Good info.

Peter Rowe



Peter

Telling a (mathematical) physicist that he's made a mistake in the
properties of solids is something to be done with caution.

From the Handbook of Physics and Chemistry, 83rd Edition, on pages 12-45ff
there's a table of the Electrical Resistivity of Pure Metals.

At low temperatures, Silver is indeed more conductive than Gold. But the
conductivities get closer together as the temperature increases. Since
we're interested in the high-temperature region for jewelry manufacture, I
suspect that the differences aren't as great as you suggest.

Also, interestingly, on p12-221, there's a table of the thermal conductivity
of Metals vs. temperature. Both are decreasing as a function of increasing
temperature. Up to 1200K (~700C), Silver is still more conductive than
Gold, but the slope of the Silver curve is steeper than that of Gold so they
may cross at some higher temperature.

So yes, you're right but I'm not totally wrong either, although in the
regime of familiar temperatures Silver and Copper do beat Gold.
Norm

.

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