Re: I would like to make my own Sterling and Argentium Metals... Is this possible ?

On Mon, 03 Mar 2008 23:00:31 -0800, in rec.crafts.jewelry Jman
<mooglieman@xxxxxxxxxxx> wrote:

Looks like a graphite mould. I suppose the graphite would help with
the oxidization wouldn't it ?

Ingots, 101

Graphite molds are usually "open faced". They produce a shape like a little
loaf of bread, or a similar block with a convex irregular top surface. That's
quite difficult to directly turn into *** metal. Fine for making little
ingots which you just wish to store or something, but impractical for making
wire or *** metal.

Also, pouring into a graphite mold, especially the small ones, is hard to get
uniform metal because the graphite is an extraordinarily good heat sink. The
metal freezes almost on contact with it. The more commonly used cast iron or
steel molds don't chill the metal so fast, so you get a more even pour. They
are normally used with a film of soot or oil, both of which make the surface
"reducing" and non-stick in nature, so the metal is not oxidized by contact with
the mold. Even without treatment, any mold surface like this will chill the
metal quickly enough, as well as not allowing oxygen to contact the surface
where it touches the mold, so oxidation next to the mold isn't an issue. Ingots
poured into steel molds, like those poured into graphite ones, often come out
bright and clean. The main advantage to the graphite molds is that metal
doesn't stick at all, and they require no pretreatment.

Wire is commonly made by pouring a long rod shaped ingot, rolling this through
grooved rollers to reduce it's size down to a manageable size, and then further
shaped and reduced by pulling through drawplates. As Ted's post mentioned, if
you've got a big and powerful enough drawbench, you can eliminate the initial
rolling stage for wire, but most people making wire start with a wire rolling
mill. Either way, the ingot to use needs to start out as a long rod shape. There
are two types of ingot mold used. For small ingots, one can get a steel
vertical mold that amounts to two plates clamped together with holes drilled
down along the boundry between them. metal poured into the holes can be removed
when the plates are seperated, yielding a round bar. The same molds also often
have another side which can produce a flat sided plate. That type of mold,
called a sliding ingot mold because the width is adjustable, can be set so the
flat plate is the same width as it's depth, effectively yeilding a bar with
square cross section. This too can be worked into wire. In both cases, these
ingots are limited in legth to the height of the ingot mold, which is usually
four or five inches or so, meaning it's good for small ingots. For longer bars,
one uses an open faced mold which amounts to a long milled groove in a steel
bar. Metal is poured into that groove, runs down it, and solidifies into a long
bar shape. These are less uniform than the first type, and can be a bit more
troublesome to roll or otherwise process into wire, especially with alloys like
silver where the top exposed surface of the bar during pouring is not only
irregular in thickness, but often quite oxidized. Still, it works.

*** metal, as suggested above, is made from flat sided ingots which are
usually made in a few inches wide or more, and equally long, or more, depending
on the size of the mold used. The thickness of the plates in most small molds
comes in between an 1/8th of an inch to a 1/4 or an inch or so. These flat
ingots may be irregular at one end, where the mold was open, but the rest of the
surfaces are nice and uniform if the pour was good, and these are then rolled
down to flat *** in the rolling mill. Without a rolling mill, you can do it
the old and slow way. Forging with a hammer. That takes skill, large muscles,
lots of endurance, and a lot of time. But it does offer you the chance to make
*** metal that varies in thickness from one part of the *** to another. Not
normally useful for jewelry, it's valuable for some metalworkers, such as those
making medeival style armor...

Large industrial producers of *** metal don't use these small molds. Instead,
they cast ingots that look more like the public image, ie a brick shaped block.
These then go to a milling machine where the raw faces of the ingot are milled
off to produce a machined square and flat sided uniform block of metal. These
then can be rolled down into quite large sizes of *** metal in industrial
sized rolling mills.

The Rolling machine looks pretty expensive.

Yes, good ones are. The cheapest little Chinese or Indian made ones start
around 250 or so, but these are good only for light duty work. If you're
planning on rolling a lot of *** metal, especially in anything other than
quite small sizes, expect to pay upwards of a thousand for a good, larger sized
flat rolling mill. And by larger size, I mean four or five inches wide. More
than that ups the price a lot more, very quickly. about the widest available
hand powered flat rolling mill I've seen is around six inches wide, and most
such mills are more like 5 inches wide. For most craftspeople making jewelry,
this is quite enough (even the much smaller ones are enough for most jewelers).
But silversmiths often like to work with larger sheets of silver, up to a foot
wide, sometimes more. That's pretty much the realm of the big industrial sized
power driven rolling mills. And yes, those are costly. Usually way out of the
reach of any individual craftsman, though sometimes you'll see a very used one
in surplus sales somewhere...

cheers

Peter
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