On Apr 19, 12:35*am, Peter W. Rowe
wrote:
On Sat, 18 Apr 2009 22:26:59 -0700, in rec.crafts.jewelry Muso

wrote:
I filled a one-tablespoon stainless
steel measuring spoon about half way full with zinc nuggets, and then
I heated the spoon with a propane torch. *The torch made a red spot on
the side of the spoon, though the zinc did not seem to be melting.

Mike, it occurs to me to wonder if you're doing any research reading prior to
your experiments? *If you had, you might have recognized that zinc, like lead,
like aluminum, or a number of other metals more reactive than gold or silver,
for oxide "dross" films quickly when melting. *Even though the metal in the
spoon quickly melted, what you saw on the outside was a mess of zinc oxide. *It
doesn't melt, so it completely hides what may be happening underneath to the
non-oxidized metal. *

Hello again, Peter. I have the book "The Charcoal Foundry", by Dave
Gingery, and the book does mention about the dross. I was holding the
torch with my left hand, though, and the spoon with my right hand, and
I wasn't sure how much working time I had to work with, so I just put
the metal in the mold dross and all. I've decided to build a holder
for my torch, though, now that it is clear to me that such a holder
will be useful. I probably will build a holder for my new three-
tablespoon capacity stainless steel ladle, also.

To some degree, this is unavoidable, since the grains/nuggets will already have
this on the surface, and when they melt, that rises to the top. *Before pouring,
you'll want to brush off that mess so you're only pouring molten metal, not lots
of mixed in oxide crud too.

Yes, I worked on that arrow head for a long time with my file, but I
still ended up with some pits and cracks. I think that with practice,
though, I should be able to get much better results. I ended up with
a good functional arrow head, but from an appearance standpoint, not
so hot.

Another fix is to use a melting flux. * Ordinary soft soldering acid flux, such
as plumbers use would do the trick just fine, *And if you use a softer flame,
and actually hold the flame over the metal, the reducing atmospher of the flame
itself (the part of the flame past the inner blue cone, but still within the
glowing part of the flame, not way past where it's just very hot gases), that
part of the flame has little oxygen, so the metal stays cleaner during melting.

I think that my mother must have remembered me joking about Twenty
Mule Team Borax, because we now have some in the laundry room. I've
been melting outdoors after sundown, by the way, so I can see the
flame better, as well as the red glow from the grain and nuggets,
which I did seperate, by the way, just to see what I had. Gingery
covers the matter of an oxidizing verses a reducing atmosphere also.
Right now I'm long on theory, but short on experience.

By the way, using clean zinc grain to begin with, unlike what you get from
murdering pennies, would drastically reduce the amount of oxide crud you have to
deal with... *(grin)

Yes, in the long run I will need to find an alternative source for
zinc. Interestingly, I recently was able to recall purchasing some
zinc from a jeweler, which I don't recall ever melting, but I remember
finding some pieces of unmelted copper from pennies in the metal. I
had forgotten completely about this until recently.

Peter *

I bought some beeswax today, and some silica sand to add to my
fireclay. In retrospect, it looks like I already had some sand, but
it is so fine-grained that I thought it was clay. I now have three
hundred pounds of sand, and fifty pounds of fireclay. Later, I will
get some coarse silica sand, and some bentonite clay.

Mike Mandaville
Bee Cave, Texas
they are actually bat caves
we have millions of bats in the neighborhood
and plenty of buzzards