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Ingot Casting


#1

hello orchid… i am somewhat of a novice silversmith, but after a
few years of buying sheet and wire i have a lot of scrap, so i want
to cast some ingots for rolling. i’ve read everything i can find on
the orchid and from books, but without a little personal instruction
from someone more experienced i’ve met with a lot of frustration,
and still no ingots. i’ve never done any casting, and all my
soldering i’ve done with propane or mapp gas. for casting ingots i
bought one of those cheap oxygen/mapp torches from the hardware
store, but the valves are so touchy that it’s really difficult to
get a nice flame, especially since i’m still trying to figure out
what a reducing flame looks like. also the oxygen bottles only last
about 20 min., and here in alaska they cost 12$ each… (i burned a
whole bottle trying to melt a 10 gram ingot, bad deal.) my crucible
is a pretty large graphite monster that seems to be a major heat
sink, so i’ve been trying to get it red hot with 2 mapp gas torches
both pointing at it from underneath on either side, while trying to
get the silver to the liquid state with the oxy/mapp torch. i got it
to the flow point a couple of times but both times it hardened
before it could even get into the mold. am i totally off the mark
here? is it my torch? my crucible? my technique? all three? for
being mostly self taught iv’e done pretty well so far, but i need
some help with this one…


#2

Doug, Save yourself a lot of trouble (and money for gas canisters)
and send your silver for refining. Rio Grande has no minimum
refining charge (so is a good choice for small amounts) but gives
you a smaller percentage of what the silver is worth. The larger
refiners (i.e., Hauser and Miller, Hoover and Strong) have minimum
refining fees that could eat a large part (or all!) of the money
returned for a small amount of metal, but return a larger percentage
of the silver value. Check out the minimum fees, weigh your silver,
do the arithmetic to see where the best deal is and send it in.

Linda in MA, where the humidity is 100%


#3

Doug,

I’m sure you’ll get plenty of replies on this but here’s my two bits
worth; your problem is not enough heat for the amount of metal you
are trying to melt. Forget about the hardware store propane tank and
get a Prest-O-Lite torch and a tank of acetelyne. Also get some
boric acid powder. You can find both of these in most any jewelers
supply catalog. I would suggest limiting your pour to perhaps two to
three ounces of metal with this setup. I often make small (1/4 to
1/2 ounce) ingots of gold for a single application, a forged ring
for example, or to draw into wire , by cutting a small rectangular
area into a charcoal block and melting the metal in that. Since you
say you are pretty much self taught, as I am as well, you should
have no problem figuring out the rest. If it weren’t for trial and
error we self teachers would be out of luck. Where in Alaska, may I
ask?

Jerry in Kodiak


#4
   Ingot casting lots of people recommend the little torch from
rio grande, but there is only one tip size available for
oxy/propane. are there other torches with changeable tips for
propane? 

Hi Doug. Actually, there is a special melting tip available for the
Little Torch, and it is available from Rio, on page 338 of their
2003 Tools and Equipment catalog. I’ve never used it, but the
company claims it will efficiently melt up to 3 ounces of gold,
bronze or silver with a 5,000 BTU output for propane. It might be
worth a try. Usual disclaimer; no affiliation with Rio Grande or
Little Torch, just trying to be helpful.

James


#5
but there is only one tip size available for oxy/propane. are there
other torches with changeable tips for propane? 

Doug, As James said, there is a ‘melting tip’ available for the
Little Torch and I have used it many times with excellent results.
Can’t say what the largest melt might be as I have never tried to
melt it’s limit but it does melt a lot of metal and does it
effeciently. Try it out.

I believe there are more than just one such tip available. Have
seen several that goes from 4 openings to 6…I have the larger.
Can’t remember where I saw the others but a check of the Smith site
should help.

Cheers from Don at The Charles Belle Studio in soggy SOFL where
simple elegance IS fine jewelry! @coralnut2


#6

Hi there,

I’ve been doing some reading into basic metallurgy and alloy
creation lately. The book I’m currently reading states that to make
the alloy, the parent metal (eg silver for a 925 alloy) is melted in
the crucible followed by the alloy additions. I was taught to make
alloys by melting the component with the higher melting point first,
followed by those with lower melting points (in the 925 alloy, copper
first followed by the silver). So I’d like to know if it makes a
difference. When you make your own alloys which do you melt first and
why?

thanks
Eileen


#7

Hello, Eileen,

I find it interesting that so many metalsmiths seem mystified by
alloying metals in their studios. I have been doing it for so many
years with positive results, I find it routine in its simplicity.

I have not found that the order the metals are put into the crucible
as important as having the correct amounts figured out. To make
sterling silver, with the traditional copper alloy, I just put them
together in a melting dish and melt them with a suitable torch,
stirring them with a carbon rod. A little borax flux is helpful.
Pour with the torch on full, into the ingot mold. Pretty basic stuff.

Alloying gold is pretty elementary, as well, and only the correct
proportions seem crucial for my work. I use ready made alloys from a
refiner here in Ca., and they all roll beautifully, draw easily, and
have great color. Just add pure gold and a big flame.

The math is easy: If you want to make 50 grams of sterling, muliply
50 by .925 (the amount of pure silver in sterling) and you get 46.25
grams. Weigh 46.25 grams of pure silver, and add copper to bring up
the total to 50.0 Don’t fudge this! If you have 10 grams of pure
gold and want to make 18K yellow gold, divide the 10 grams by .75
(the amount of pure gold in 18K) and you get 13.33. Add 18K alloy to
your 10 grams of pure gold until you reach the 13.33, and you’ve got
13.33 gr. of 18K gold. Melt, add a bit of flux, stir with a carbon
rod, pour into your ingot mold with the flame on high.

Hope that helps.

Jay Whaley UCSD Craft Center


#8

My thought is that the bulk of the material will be the ‘parent
material’. It will take awhile to get the silver flowing, of course
hotter torches (Oxy mix and the like) make this less of an issue.
Once you have it molten it will not take too long to melt the
compents (even despite their higher Melting Points, especially due
the molten silver). I would just be careful to add enough heat so
that it will actually melt and mix since you won’t be able to see it
as well. (I wopuld hate to hae the little bit all nice and flowing,
put in all that cold silver with the heat most likely out of the way,
it solidifying again, and laying the heat to everything to get it to
flow).

Just a thought though.
David Woolley
Fredericton, NB, Canada


#9
        I find it interesting that so many metalsmiths seem
mystified by alloying metals in their studios. 

Hi Jay;

I’ve been alloying my own gold alloys for a long time. I would never
try to make sterling. Pointless to go through the challenge of
melting copper for the small amount of money saved. But the savings
of alloying your own gold are significant. That said, I’m thinking
of abandoning the job and resorting to pre-mixed alloys. I have
already stopped making my own white gold alloys due to the difficulty
of melting the alloy and the problems of oxides. If you don’t get the
alloy thoroughly mixed into the gold, you’ll be sorry as your
casting will have bits of unmixed alloy in it, usually nearest the
sprue. I know, you can melt and pour shot, but a second melting
increases the problems of gasses in the metals. I’m at the point
where I’m not willing to accept any amount of risk if it is at all
avoidable. A bad casting means re-carving, re-casting, and that means
cutting my pay in half.

David L. Huffman


#10

It is considered proper practice to add the component metals in
order of their melting point. So for sterling one would start with
the copper as it has the highest melting point. If you do it
otherwise you may have problems with poorly mixed alloy as some of
the higher melting point materials may not have completely dissolved
into solution by the time you pour the ingot. also with low melting
point components like zinc you really do want to add them at the end
so there is as little loss as possible due to vaporization of the
metal.

With that said you need to take into consideration your method of
melting. The above applies more to larger amounts of metal in a
crucible furnace with a protective atmosphere covering the melt.

If you are alloying small amounts of metal and melting with a torch
you may want to melt the silver first to reduce the amount of oxygen
the copper picks up in the melting process but you will need to keep
the alloy molten for a longer period of time than if you start with
the copper first just to make sure all the copper dissolves into
the melt and is thoroughly in solution.

Jim Binnion

James Binnion Metal Arts
Phone (360) 756-6550
Toll Free (877) 408 7287
Fax (360) 756-2160


@James_Binnion
Member of the Better Business Bureau