Melting impure silver causes a lot of spluttering.

[Amol Gupta]

So I melt my silver in a graphite crucible in a resistive heating furnace.

If my cement silver is pure I do not observe any sputtering and the melt is well behaved.

But if my cement silver is impure(close to 80%) I observe a lot of spluttering and I see a lot of silver attached to the lid of the furnace the sputtering subdues after some time.

I'm pretty sure I'm not the first one observing the phenomena id like to know what other members use to avoid such sputtering(if something like this is possible) and why is it the sputtering only occurs for impure silver while the pure silver(98-99%) behave very well(no sputtering).

 

[anarxi]

So I melt my silver in a graphite crucible in a resistive heating furnace.

If my cement silver is pure I do not observe any sputtering and the melt is well behaved.

But if my cement silver is impure(close to 80%) I observe a lot of spluttering and I see a lot of silver attached to the lid of the furnace the sputtering subdues after some time.

I'm pretty sure I'm not the first one observing the phenomena id like to know what other members use to avoid such sputtering(if something like this is possible) and why is it the sputtering only occurs for impure silver while the pure silver(98-99%) behave very well(no sputtering).

I don't know of any other methods other than to re-dissolve the silver and make it purer.

I have seen that silver cement is also pressed into tubes (for example, using a syringe) and they are melted, so it is less likely to scatter....

 

[Amol Gupta]

I don't know of any other methods other than to re-dissolve the silver and make it purer.

I have seen that silver cement is also pressed into tubes (for example, using a syringe) and they are melted, so it is less likely to scatter....

The sputtering I mention off is during the molten state.

 

[Yggdrasil]

The sputtering I mention off is during the molten state.

This is usually because of reactions with impurities during the melt.
If there are Oxides, Nitrates or other substances present, there can be many "interesting" reactions.

 

[Amol Gupta]

This is usually because of reactions with impurities during the melt.
If there are Oxides, Nitrates or other substances present, there can be many "interesting" reactions.

This is my best guess, aided by the fact I am using a graphite crucible.
Would adding borax to the melt reduce the sputtering...?

 

[Yggdrasil]

This is my best guess, aided by the fact I am using a graphite crucible.
Would adding borax to the melt reduce the sputtering...?

If it creates a "lid" on the melt it can contain it maybe.
But I'm not sure how well Borax plays with Graphite.

What kind of impurities do you have in there?

 

[Amol Gupta]

If it creates a "lid" on the melt it can contain it maybe.
But I'm not sure how well Borax plays with Graphite.

What kind of impurities do you have in there?

If it creates a "lid" on the melt it can contain it maybe.
But I'm not sure how well Borax plays with Graphite.

What kind of impurities do you have in there?

Majority of it being copper.

 

[Yggdrasil]

Majority of it being copper.

There is no reason that clean Copper should cause this.
Are there Oxides, Nitrates or moisture in it?
Moisture WILL cause explosions like this.

 

[Amol Gupta]

There is no reason that clean Copper should cause this.
Are there Oxides, Nitrates or moisture in it?
Moisture WILL cause explosions like this.

I do admit I have moisture in my melt, but I'm not sure why is it only there in the impure melt, my clean cement silver 98-99% does not exhibit such explosions.

 

[Amol Gupta]

There is no reason that clean Copper should cause this.
Are there Oxides, Nitrates or moisture in it?
Moisture WILL cause explosions like this.

Yes oxides for sure I am very confident I have oxides in my melt something that could not be washed by hot water rinse, the reason for impure silver

 

[goldshark]

This is my best guess, aided by the fact I am using a graphite crucible.
Would adding borax to the melt reduce the sputtering...?

Borax loves to consume Graphite crucibles. Pure Graphite crucibles should only be used for metals. A silica/Alumina crucible is better suited for your melts. All components of the melt should be dry, to reduce the amount of steam expulsion.

 

[goldshark]

Borax loves to consume Graphite crucibles. Pure Graphite crucibles should only be used for metals. A silica/Alumina crucible is better suited for your melts. All components of the melt should be dry, to reduce the amount of steam expulsion.

Also try adding a bit of Carbon to the melt. Flour works wonders on Oxides. About 1 gram per 11 grams of oxides ( not already reduced metals ).