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Cleaning silver during melting

#1

Hi again

is there anything i can add to the silver to clean up the silver when
i melt it i normaly put i pinch of borax in with my scrap. i used to
work in a foundry and when we refilled the casting pots we put in
some power and when the molten metal was mixed all the scum used to
come to the top which would then be scooped off which would leave the
metal clean and gas free so the castings would be perfect, the thing
is i can remember what the stuff was called, can anyone help, also
apart from borax what else can be used when melting scrap silver. i
saw something somewhere talking about salt peter/saltpetre (dont know
which is correct ) in melting metal. and im sorry to keep goin on but
can anyone tell me what the use for argoflux is.

many many thanks
jason

#2

Hi jason,

a pinch of flux normally does the job, it takes oxygen away from the
metal and with it most impurities. What you mixed in with metals in a
foundry would vary according to the metal being melted, you would add
phosphor copper to bronze for example to clean and degas it. You can
use carbon to clean your molten metal, I stir aluminium with a big
carbon spoon before casting but there are proprietary fluxes.
Saltpeter will in theory clean your silver but it normally ignites
too readily [main component of gunpowder]. Argoflux is a trade name
for a borax based flux, it has a small amount of copper salts added
if I recall. you can use it as a silver solder flux or to reduce
firestain or for fluxing your casting melting as with borax.

Nick

#3

This thread is annoyingly familiar to me as it’s a problem I also
suffer from. I get this problem when making my own sheet -though not
every time - but I have encountered it with purchased stock too. I
assumed that I had overheated the metal, causing the blistering. Now
I’m wondering if I’m getting gas bubbles when I’m melting my silver.

Possible lightbulb moment! I’ve been coating the silver to be melted
in Pripps flux, whereas I used to drag it through the sludge at the
bottom of my super-saturated boric acid in alcohol jar. I think I’ve
only been getting this problem since changing flux. May be
coincidence, I’m not sure.

Helen
UK