Back to Ganoksin | FAQ | Contact

Weird casting question - heavy zinc foil


#1

Hey everyone, I’m back for a bit, I keep telling myself I’ll quit
jewelry art but never can manage to sell all my equipment or stones,
now I’m finding myself back in the garage making some new ideas and
having fun again.

Anyway…I ran out of Precious Metals S-88 alloy which I love and
had to alloy my own sterling again. Dreaded seeing those grey
castings again…anyway, I had a friend awhile back who gave me
some 50/50 zinc, fine silver alloy and told me to pop a pea size into
the melt at the last minute and it would de-ox the melt. It sorta
worked, usually it would burn off real fast and once in awhile I’d
get a white silver casting. The S-88 de-ox alloy is what I finally
got into.

Anyway, I had some zinc heavy foil left over from my friend and put
a folded up piece under the copper, under the silver in the crucible,
I cast and got the grey casting as usual. So the next cast I put a
fairly chunky piece of the foil in there again and got a completely
bright silver casting, something I never got conventionally. Does
anybody ever do this as a regular procedure and are there any
drawbacks to this? I’m assuming most of the zinc gets burnt off?
Also, most importantly does anyone know where to get this heavy zinc
foil? Its gotta be cheaper than S-88 alloy. Any suggestions would
as always be greatly appreciated. Dave Stephens


#2

I usually include 6.66% zinc when alloying gold. It definitely cutts
down on oxidation. I have noticed that overheating my metal acuses a
white smoke to come off of the melt as well as begin to turn my gold
pink. Along with the color change, I get a metal that oxidizes all
together too easily during soldering operations.

I don’t do much silver work, but I have included a little zinc with
my copper sometimes when alloying. I usually just eyeball it. Perhaps
6.5%copper with 1% zinc to make sterling.

There is no science here. Just my personal observations and
experience.

Bruce Holmgrain
JACMBJ


#3

Hello Dave,

Zinc is a very good for deoxidising silver and gold. It needs to be
added in the melt just before pouring. As long as you keep under the
1-2% addition it will burn and eat up the oxides. and will not effect
the alloy content. You can use normal zinc use on roof gutters.

Martin Niemeijer -


#4

Dear Martin, It might be wise to caution people to be extremely
careful about melting zinc inasmuch as most zinc contains cadmium
which is extremely poisonous. Ron at Mills Gem, Los Osos, CA


#5

Dear Ron, Do not over-react. The contains of cadmium in zinc is very
low. The electro refining process which is used to get zinc is very
efficient. Therefore the cadmium contains is below 0.05%. The cadmium
is to expensive to leave in the relative cheep zinc.

Also when you are melting old silver, you are not with your nose
above the melting pot. Common sense people are melting in a
ventilated room or under an exhaust hood, so the change to inhale
some is nil. The more trouble with the new roof zinc is, that
nowadays titanium is added to improve the weater resistance of this
zinc. This amount Ti (0,2%) can cause intercristaline hardening of
the gold alloy. But also this amount is to low and the improvement by
burning the zinc is much higher than the increased hardness by the
titianium. Martin Niemeijer