# Silver melting issues or pouring actually



## DagmaraDag (Nov 6, 2017)

Hi,

I am going insane! I am trying to pour silver into a Durston combination bar form 4.5mm x 50mm x 80mm. It was a scrap silver therefore I am not sure if I mixed 999 with 925 - does it matter when melting? So I bring the silver in my crucible to a nice liquid form, I heat the mold and when I pour into the mould it does not come out as a nice solid, even and regular bar. It looks like silver expanding foam in a mini version. What do I do wrong? I tried 5 times with no success so far. :evil:


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## jimdoc (Nov 6, 2017)

http://goldrefiningforum.com/phpBB3/search.php?keywords=pouring+silver+bars


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## g_axelsson (Nov 6, 2017)

Sounds like oxygen absorption, when the silver solidifies the oxygen is released like when you open a soda bottle but with red hot molten metal instead. This is a sign of high purity and the reason silver smiths always alloys the silver with copper. This isn't an effect that you can see in alloys, sterling silver for example.

The only way of melting pure silver without absorbing oxygen is with a protective atmosphere (inert gases or reducing atmosphere) or in vacuum.

After writing all that it hit me, there could be a simpler reason behind your problems...

Another reason of your problem could be a cold mold, the surface of a mold is absorbing gases and water vapor from the atmosphere. When you add hot metal those gases are released and adds surface imperfections. Did you heat your mold before pouring?

Göran


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