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Making Sterling Alloy for Casting


#1

Hi Orchid,

I’m still new to casting, but having noticed the very high cost of
sterling casting grain, I am wondering about making my own sterling
alloy. Fine silver is easily available at market value, and copper
is cheap, so is there any reason why I shouldn’t make my own
sterling alloy? Does it need to be done in an inert atmosphere to
prevent oxidation and loss of copper, or can it be done with a
melting torch?

Thanks for your help,
Douglas and Sarah
Eclipse Gems and Design


#2

You certainly can make your own casting alloy, It will be difficult
to make grain that is as clean and oxygen free as the product from
the better suppliers but you can do it. Expect to have castings with
more gas porosity problems than when using clean new shot from a good
supplier. But if you are careful with your torch and always keep the
whole area of the metal covered with flame at all times you can make
ok casting alloy. Making shot without trapping a bunch of water in it
is a little tricky and you will oxidize the alloy as you pour it.

James Binnion
@jbin


#3

The biggest problem with making your own sterling casting grain is
making sure the alloy is true sterling. I have overcome the oxidation
and porosity problem somewhat by alloying in a charcoal vessel. As for
the cost, I think the quality concern override the cost of buying new
casting grain.

Peace,
Richard


#4
Expect to have castings with more gas porosity problems than when
using clean new shot from a good supplier. 

I absolutely disagree with this. If I am casting 10 grams of 14 kt,
red, yellow or white (Fell’s winter white), I take 5 grams of old
metal, multiple 5 x .585 which gives you the 24 kt needed, add to
that alloy till that weights 5 grams, put all in a casting crucible,
torch, flux well and cast. I do NOT make casting grain which I then
cast with.

I have nothing but porosity free castings. My castings are so easy
to polish I have my new employees recently hired, not much experience
with finishing casting, polish these, and they are done polishing a
simple gold ring in about…20 minutes from casting to finish polish.

Richard Hart


#5

Expect to have castings with more gas porosity problems than when
using clean new shot from a good supplier.

 I absolutely disagree with this. If I am casting 10 grams of
14  kt, red, yellow or white (Fell's winter white), I take 5 grams
of old metal, multiple 5 x .585 which gives you the 24 kt needed,
add to that alloy till that weights 5 grams, put all in a casting
crucible, torch, flux well and cast. I do NOT make casting grain
which I then cast with. I have nothing but porosity free castings.
My castings are so easy to polish I have my new employees recently
hired, not much  experience with finishing casting, polish these,
and they are done polishing a simple gold ring in about...20
minutes from casting to finish polish. 

Richard you are talking about gold and the question was about making
sterling casting grain, two totally different animals. It is
certainly not worth arguing over but I guarantee you have porosity
in your castings. You may not have enough to cause you a problem but
there is always some level of porosity in a cast product it is the
nature off the beast. The real concern is how much and where it is.

Regards,
Jim


#6

Richard,

I read your recent message on how you alloyed 14K gold for your
"porosity free" castings and thought I had written it myself!

I’m on the same page with you on your technique for alloying metal
for your castings, and I too use David Fell’s alloys, which I love.
Their “14K soft white” alloy is a killer white, and draws well, too.

I don’t see the point of making casting grain and then turning
around and melting that in the casting crucible.

Seems like a wasted step to me, and I’d rather keep from heating
that alloy any more than neccessary for the casting at hand.

I will also add, that I’m always open to learning more tricks to
improve our metalsmithing processes and products.

—Jay Whaley UCSD Craft Center


#7

When we are talking about porosity, what exactly are we talking
about?

Are we talking about something detected with magnification or what
I have known as problematic porosity, where the metal surface has
pits, voids, or will not take a high polish because it has an area
that is a sponge-like and can be seen by the naked eye and has to be
welded or remade?

The method for casting gold I use produces pieces that show no signs
of porosity with the naked eye.

I have alloyed my own deox silver, and sterling, and cast
200,000-300 000 thousand pieces that had no visible signs, with the
naked eye, of porosity. Yea, I use acetylene to cast with!

Torch melt, centrifugal, by guess and by golly.

The biggest problem I ever had was using pure silver that was
recovered from photographic film. It was contaminated with something
that gave me one whole casting 9-3 x 7 flasks with at least 75
pieces in each can that was so brittle that you could break it like
dry spaghetti.

Take chances, make mistakes, play, try not to hurt yourself,
experiment, learn. Try doing things that “they” say you can’t do.

Then you can do things “they” can’t.

OCD and persistence helps.

I once repaired a pre-Columbian gold bat. When I repaired it, it had
broken, because of porosity when it was cast.

Point being, in the past there was not the technology to support the
standard that we feel we have to live up to now. There were not
loupes, there were not microscopes, there were not laser welders.

When I first started out, I made some things that I would be proud
of, and I made some stuff that I would be embarrassed by. And someone
eventually bought something, that had porosity or fire scale and
loved it and wore, and no one died or got sued.

Saw that customer again, and they never complained about the
workmanship, they bought more stuff, and sent their fiends. I am not
going to hell for not being able to achieve technical perfection with
each and every piece.

It is good to strive for perfection, and it is good to know when to
settle for lower standards when you know that your customer is
getting a perfectly fine piece.

I have had pieces come back that had cold solder joints. Not many,
but some.

Richard Hart