<p>I would suggest charcoal and no flux. Keep molten time to a minimum. Charcoal is used on molten lead for long periods to reduce oxidation. For many copper alloys , hydrogen absorption is a problem ; it evolves during freezing causing porosity. I read in ASM Metals Handbook that molten silver may absorbs oxygen causing porosity. Charcoal should provide some protection from both H and O..
Borax seems pretty easy to get in the US. However, long ago I mixed flux to make a slag for copper alloys , it primarily contained : soda ash ( sodium carbonate), beach sand ( silica), and fluorspar. There are a number of sites on the net that sell proprietary fluxes ( for copper alloys). And one site gives info on the flux
 components -  911 metallurgist. </p>

CC BY-SA 4.0
2020-04-07T18:04:19.933Z
Could you please expand on the possible method of usage a bit? Would I just sprinkle it on? Wouldn't it just burn? It ignites in air at around 350°C, and we are talking about over 1500°C.
Martynas Žiemys
CC BY-SA 4.0
2020-04-07T18:38:45.433Z
First get a new reference; silver melts at 960.8 C. Any of the typical alloys like Cu will lower the melting temperate.  For casting 50 C should be enough super-heat. Even less with a hot investment mold,  The charcoal will slowly burn generating a CO + CO2 atmosphere . I remember about a 1 to 2 inch deep charcoal bed. Charcoal granule size  of roughly 1/4 ". No fans blowing at the crucible.
blacksmith37
CC BY-SA 4.0
2020-04-07T19:04:12.960Z
I know what temperature silver melts at, however if I understand it correctly it must be higher in order to flow to the mould successfully and the temperature of the torch I am planning to use is advertised to be 1900°C(so I expect it to be at least something above 1500°C). Should I lower the temperature by adjusting how much air gets to the flame? Have you tried it yourself? Don't get me wrong - I really appreciate the advice and will give it a go, I am just curious what to expect.
Martynas Žiemys
CC BY-SA 4.0
2020-04-07T19:22:04.080Z
The 50 C super-heat should handle it unless you are trying to cast  thin section like 1 mm /0.040".My only experience was commercial except watching a dental lab pour Vitallium ( Co + Cr) and they used no flux for fast induction melting.
blacksmith37
CC BY-SA 4.0
2020-04-07T15:36:08.107Z
2020-04-07T19:14:20.697Z
2020-04-07T19:14:20.697Z
blacksmith37
<p>I am new to jewelry. I would like to try casting silver (pure) in so called green sand. In my research I see that it is recommended to use some sort of flux while melting silver. The most popular and widely available without a doubt is borax (sodium tetraborate if I am not mistaken), however it seems to be for some reason (toxicity maybe) illegal where I live and I cannot get it that easily. </p>

<p><strong>Are there any common materials that can be used as flux for silver melting instead of borax?</strong> </p>

<p>I have seen sodium carbonate (wash soda/calcined soda) being sold as some sort of flux and I have read something about sodium hydroxide (lye) being used as flux in some applications. Would these materials be suitable/better than nothing for silver melting or should I not worry about it at all and pure(ish) silver should not oxidize anyway? Or is there anything else that might work?</p>

<jewelry><casting>
What else can be used as flux instead of borax for silver casting?
Martynas Žiemys
# What else can be used as flux instead of borax for silver casting?

(Asked by: username_0 on 2020-04-07)

I am new to jewelry. I would like to try casting silver (pure) in so called green sand. In my research I see that it is recommended to use some sort of flux while melting silver. The most popular and widely available without a doubt is borax (sodium tetraborate if I am not mistaken), however it seems to be for some reason (toxicity maybe) illegal where I live and I cannot get it that easily.

**Are there any common materials that can be used as flux for silver melting instead of borax?**

I have seen sodium carbonate (wash soda/calcined soda) being sold as some sort of flux and I have read something about sodium hydroxide (lye) being used as flux in some applications. Would these materials be suitable/better than nothing for silver melting or should I not worry about it at all and pure(ish) silver should not oxidize anyway? Or is there anything else that might work?

**Tags:** jewelry, casting


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## 1 answers

### Answer by username_1 on 2020-04-07. Score: 3

I would suggest charcoal and no flux. Keep molten time to a minimum. Charcoal is used on molten lead for long periods to reduce oxidation. For many copper alloys , hydrogen absorption is a problem ; it evolves during freezing causing porosity. I read in ASM Metals Handbook that molten silver may absorbs oxygen causing porosity. Charcoal should provide some protection from both H and O..
Borax seems pretty easy to get in the US. However, long ago I mixed flux to make a slag for copper alloys , it primarily contained : soda ash ( sodium carbonate), beach sand ( silica), and fluorspar. There are a number of sites on the net that sell proprietary fluxes ( for copper alloys). And one site gives info on the flux
components - 911 metallurgist.

> **Comments:**
> **username_0**: Could you please expand on the possible method of usage a bit? Would I just sprinkle it on? Wouldn't it just burn? It ignites in air at around 350°C, and we are talking about over 1500°C.  
> **username_1**: First get a new reference; silver melts at 960.8 C. Any of the typical alloys like Cu will lower the melting temperate.  For casting 50 C should be enough super-heat. Even less with a hot investment mold,  The charcoal will slowly burn generating a CO + CO2 atmosphere . I remember about a 1 to 2 inch deep charcoal bed. Charcoal granule size  of roughly 1/4 ". No fans blowing at the crucible.  
> **username_0**: I know what temperature silver melts at, however if I understand it correctly it must be higher in order to flow to the mould successfully and the temperature of the torch I am planning to use is advertised to be 1900°C(so I expect it to be at least something above 1500°C). Should I lower the temperature by adjusting how much air gets to the flame? Have you tried it yourself? Don't get me wrong - I really appreciate the advice and will give it a go, I am just curious what to expect.  
> **username_1**: The 50 C super-heat should handle it unless you are trying to cast  thin section like 1 mm /0.040".My only experience was commercial except watching a dental lab pour Vitallium ( Co + Cr) and they used no flux for fast induction melting.  

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