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Casting help


#1

*** trying until I get through :-] ***
Hi all,

The only casting I have done is sand casting and cuttlebone
casting and I want to hire someone to make duplicates (almost) of
several cuttlebone casting that I have done. I say almost because
I may want them to be a little thinner than the original.

Obviously, it’s the cuttlebone pattern that I want to keep. So I
know that doing a sand casting of it won’t work. Also, as a
fabricator, I know that I need to add some casting work to my
line to raise my “take home pay”.

What would be the best way to keep that pattern and produce 30-50
pieces at a time. I haven’t talked to any casters and if this is
a project that someone in the group could take on it would be
wonderful. Otherwise, I’ll take all the I can get
and hit a casting house in Boston or Providence,RI (suggestions
anyone?)

Kathleen Parker (MoonScape Designs) kparker001@aol.com


#2

Hi Kathleen, If I understand what you are trying to accomplish,
you could very easily, as well as inexpensively, use a liquid
mold compound. It is available from probably every supplier, and
provides nice molds that last a very long time. I have used them
for many years and find them to be quick and easy to use. Good
Luck, Curtis


#3
 The only casting I have done is sand casting and cuttlebone
casting 

Hi! I’ve never cast a thing, I work with sheet and wire. Now,
that I’ve done it for a few years, I have a lot of cut-off stuff
left over. I’ve heard that I can melt this down. I have a
melting vessel <sp???> Crusible (sp?) I also ordered some
borax. How do I melt my stuff down??? What do I do with the
borax? Any help would be greatly appreciated! (heck, I’m not
even considering the filings at this point!)

Thanks in advance!!!


#4
   I have a lot of cut-off stuff left over.  I've heard that I
can melt this down.  I have a melting vessel <sp???> Crusible
(sp?)  I also ordered  some borax.  How do I melt my stuff
down???  What do I do with the borax? 

If you would like to see a rough explanation of cuttlefish
casting, I wrote an article for Delphi Art and Crafts Forum on
it: http://www.delphi.com/crafts/cuttlefish.html . And that and
sand casting are also covered in many jewelry books such as Tim
McCreight’s Practical Casting and Oppi Untracht’s book.

The borax you just take a pinch of and sprinkle over your molten
metal.

Jill
@jandr
Jill Alessandra Jewelry
http://members.tripod.com/~jilk/


#5
  I have a lot of cut-off stuff left over.  I've heard that I
can melt this down.  

G’day, R - I work almost entirely with sterling and fine silver,
and carefully save all my scrap pieces - I use a piece of soft
leather beneath the cutaway in my bench and sweep the scraps and
filings into an old slide box which has the bottom cut out and
replaced with metal gauze from an old kitchen flour-sieve. This
separates the filings from the larger pieces.

I use a flat crucible (available from any of the jeweller’s
suppliers) to melt the silver with a small oxy-propane flame.
You’ll need a rod mould if you intend to make wire, and/or a
mould to make bar-strip. These are also available from the
suppliers. I simply place my little flat crucible on a piece of
pumice (NZ is volcanic!) or a firebrick then heat it from above
with the scrap in place - using a flame that has a tinge of
yellow (which helps avoid oxygen dissolving in the molten silver,
which it likes to do) I have already heated the iron mould and
clamped the two halves together with a small C clamp, and
arranged things so the mould tilts at about 45 degrees.

When the silver is really molten, I sprinkle a little flux (I
use Easy-flo, but borax is quite good) on the liquid silver, and
keeping the flame playing on it, carefully pick the crucible up
with a pair of strong pliers and gently pour it into the DRY!!
mould. (Practice this!) If the mould is wet you’ll get the silver
shoot out again over your workshop, so never have the mould
opening pointed towards you! If all has gone well you will have
silver rods or thin bar. Now you need to ‘get round’ a jeweller
who has a rolling mill to enable you to reduce the bar and rod to
a thickness able to be drawn into wire or sheet. I’ve got a good
mate who lets me use his.

I use a home-made rod and bar mould, a home-made drawbench, and
even home made wire dies (6mm for tube-making down to 2.5mm, for
my commercially made dies take over from that size)

One more point: try and keep scrap which has been silver
soldered, separate . Silver solder contains zinc, and this can
cause minute bubbles in recycled silver, which in turn produce
tiny Vee shaped ‘jags’ in the wire. I save that up and when
there’s enough I cast it together with filings into a bar then
refine it electrolytically to get pure silver - which I make
into thin strip for bezels. But then; being retired, I have
spare time to recycle silver rather than buy it! No professional
jeweller could afford to waste time recycling - other than gold.
If you want to know more, just give me a shout, eh? Cheers
now,

       / \
     /  /
   /  /                                
 /  /__| \      @John_Burgess2
(______ )       

At sunny Nelson NZ in late winter/early spring with lambs, daffs, tree
blossoms etc. Cold starry nights, cold sunny days


#6

John,

Your ingot casting method is mostly familiar to me, but when I
was at GIA I was taught to oil the mold, and then to heat the
mold to smoking…I’m assuming from your description that it was
partly to ensure that there was no residual moisture in the mold,
but I was also told it was to aid in the release of the ingot…

Any thoughts on this?

kat
kht@vincent-tanaka.com


#7

Definitely oil the mold! This eliminates a lot of problems
encountered with dry mold plates and insures a smooth flow of
metal. i experimented using dry and oiled molds but oiled won.
Martdoc@southernet.net


#8
  I have a lot of cut-up stuff left over. I've heard I can
melt this down.

I’m no expert on this, so I’m writing this from the perspective
of someone who doesn’t know the “right” way. A goldsmith showed
me a nifty way to melt small amounts of metal down without a lot
of tools, equipment and four hands. Very lo-tech, affordable,
non-threatening and very easy:

Scrape a shallow depression about the size of a quarter in a
charcoal block, with a small “channel” going off of it on one
side in case there’s “overflow”. Have a second charcoal block
handy. Put your metal scrap on the first block and heat until it
starts to melt, then sprinkle a very little borax (available in
the detergent section of the grocery store) on the metal as a
flux. Stir the puddle with a wooden pencil when it’s fluid (if
you don’t have a carbon stirring rod). When it’s completely fluid
and ready to “pour”, flatten the puddle with the second charcoal
block. Voila - an ingot. Smaller than pouring a lot of metal into
an ingot mold, but easier, faster, and thinner, so takes less
time to roll out. Also, you don’t need a casting torch, or a
super duper casting tip. The charcoal and the wood + graphite of
the pencil keep the metal from oxidizing.

Just an alternative method to pouring into an ingot mold and
using a crucible. Hope this helps.

Rene
No. Calif.


#9

I’m having some problems casting and need help. When I burn out and
then vacuum cast, my castings get a black patina on them. It is very
hard to remove with a wire brush. In the most severe cases, the
castings come out with a loss of detail, and some with investment
stuck (fused) to them that will not even chip off. Please note that
I am casting with silicon bronze.

Has anyone out there experienced similar problems? I thought it
could be a tempature problem, ie the flask is heating up too hot
before casting. The kiln reads at 1150 when I remove the flask. I
was told not to go above 1300 because this will break down the
investment, causing sulpher to be released and stain the casting. Is
this what’s happening? Or could it be the metal is too hot. I was
given a m.p. of 1850 for the silicon bronze, and am heating it in a
kerr mini-furnace to 1900 which doesn’t seem too excessive…

If anyone has any tips they would be much appreciated.

Thx
Jim


#10

This is normal as far as I have experienced. But you dcan go to 1500
on the kiln and then pour the metal with the flask at 900 to 1000
degrees. The bronze should be at 2150. To clean off the scale use
sulfuric acid or bead blast it.

Cynthia


#11

Hi, wire brush wont take off the black , you need to pickle it out.

Ed Dawson
Maine Master Models
http://www.goldandsilversmithing.com


#12

Jim, I am not familar with casting metals other than silver and gold.
If silicone bronze has copper in it the copper will combining with
oxygen to form cupric and cuprus oxide (fire scale). The black
coating you are getting is probably cupric oxide. This normally can
be removed in a pickling bath. Cuprus oxide is fire scale and does
not show up until you try to polish the piece. If you are
polishing the piece you might get a better polish if you try my
simple fire scale prevention technique I have developed. The
process will prevent both types of oxides. Be glad to send you a
copy of my description of the process if you send me your address
(free of charge). The process is very simple. It calls for scrap
wax, two solid soldering pads and a flask bigger that the one you
are casting in. The technique produces a reducing atmosphere around
the piece as it cools before quenching. The wax combines with the
oxygen to prevent it from combining with the copper.

I believe the loss of detail can be caused by several things. The
burn out may not be complete leaving ash in the mold or the metal is
not hot enough and chills before it completely fills the mold. In
either case you will have sections of the casting that are not
sharp. Ash normally leave a pitted surface on the casting.

Burn out temperature should not go much above 1300 degrees.
Maintain the burn out temperature for a longer time if there is a
lot of wax in the mold. I normally fill my burn oven with flasks
and find that 8 hours at the burn out temperature produces a great
burn out. Anything less has caused me problems.

I some times get investment that builds up a hard surface on silver
wires that I use as reinforcing rods to hold the investment in the
hollow portion of my pottery. I have a suspicion that the hard
investment that you are getting around the casting is caused by
copper migrating into the investment after you pour the metal. No
proof just a feeling.

Hope this helps.
Good luck
Lee Epperson


#13

Hi Jim, A black patina on your silicon bronze after break out is
normal. Regular pickle will work ok most times, but I like to use
full strength muriatic acid. Be sure to have a powered ventilation
hood if you use the muriatic or do it outside and stand up wind. You
can find muriatic acid at your local hardware store.As with any
strong acid, it is important to use gloves and lots of caution.The
crusty investment on your casting does indeed suggest either your
investment or your metal is too hot. In fact, I’m casting some
bronze today at about 1150 F. The pieces I’m doing are for a bagpipe
maker that. His parts have become popular with other bagpipe makers
so we cast a fair amount of these widgets. They are fairly thin and
tubular. The silicon bronze is quite fluid when molten an so it
doesn’t need super heating. I have seen metal fuse to investment and
get that nasty crust like it has been on the bottom of the ocean for
a thousand years! If your piece is not so thin, for instance, a
large mans ring you can lower your flask temp to 950F. For the metal
temp it depends if you are torch, electric or induction melting. If
you are torch melting you want to get the metal molten and pour. I
realize for vacuum casting you’ll want it hotter than for
centrifugal. If you have super thin pieces and the temps want to be
hot just to complete the cast, you may have to switch to high temp
investment. Hope some of this helps. John, J.A.Henkel Co.,Inc.
Moldmaking Casting Finishing