latest silver bar
- Thread starter Jimmi
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Jimmi
Well-known member
philddreamer
Well-known member
Very nice indeed! 8)
What type of torch are you using?
Phil
What type of torch are you using?
Phil
Jimmi
Well-known member
I am melting with oxy acetylene and heating the mold with map. I turn the oxygen down on the oxy acetylene rig. But I'm still getting a bit of absorbtion. We are thinkin about placing a heated mold in a box and flooding the box with argon or some other inert gas to avoid the oxygen. Does anyone have any thoughts on this idea? Any suggestions would be appreciated.
lazersteve
Well-known member
I do see videos of silver pours where there is a second torch on the mold and the pour is done with the second torch running, using up the oxygen, try pouring through a second flame and remove the second flame when the silver has frozen.
Jimmi
Well-known member
Yeah we have been pouring through the second torch flame. Still getting a little bit of absorption though. Oh and thanks for the link to that thread Steve.
In no particular order.
1. Less is more. Your pour temperature on large 100 + oz bars need be no higher than 990*C.
2. Melt it quickly and don't re-melt it. Every time you melt it, it gets dirtier, more silver volatilizes away, and more oxygen is absorbed. Very recently, I've seen very fine (5N+ silver) melted in our bench top muffle furnace literally boil when it cooled because it had been left sitting in the silver furnace overlong at 1050 C.
3. When pouring, make sure your mold is free of moisture or excess oil.
4. Pre-warm your mold to at least half the temperature of the silver coming into it.
5. When pouring, wear gloves and appropriate safety equipment so that you're not dropping hot crucibles and the like in the event of something going wrong (i.e. steam explosion, you have an almighty sneeze and slosh it around, etc.)
6. Sooting the mold with acetylene does help with surface finish (even on graphite) and allows for easier dump out on molds with less draft; just be sure not to breathe it in, as it's a bunch of nasty stuff!
7. If you have a heavy hand with the borax or carbonate, add clean white silica to thicken the slag. It does not take much to do this, but it will hold the slag to the crucible and keep it out of your mold.
8. Have a steady hand. Quickly but steadily empty the crucible into the mold. Good tongs are essential.
9. If you want a mirror finish, have a fan flame set up over your molds. This disturbs the surface movement and organization into crystallites (or contraction patterns) and prevents oxides from appearing.
10. Put a bunch of paper towels or cotton rags in the bottom of your stainless quench bucket. When you dump your molds and the bars out and into the quench bucket, it'll keep them from getting dinged or marred.
To the pros: I have had success de-oxing silver with hydrogen or methane gas blown through it.
Lou
1. Less is more. Your pour temperature on large 100 + oz bars need be no higher than 990*C.
2. Melt it quickly and don't re-melt it. Every time you melt it, it gets dirtier, more silver volatilizes away, and more oxygen is absorbed. Very recently, I've seen very fine (5N+ silver) melted in our bench top muffle furnace literally boil when it cooled because it had been left sitting in the silver furnace overlong at 1050 C.
3. When pouring, make sure your mold is free of moisture or excess oil.
4. Pre-warm your mold to at least half the temperature of the silver coming into it.
5. When pouring, wear gloves and appropriate safety equipment so that you're not dropping hot crucibles and the like in the event of something going wrong (i.e. steam explosion, you have an almighty sneeze and slosh it around, etc.)
6. Sooting the mold with acetylene does help with surface finish (even on graphite) and allows for easier dump out on molds with less draft; just be sure not to breathe it in, as it's a bunch of nasty stuff!
7. If you have a heavy hand with the borax or carbonate, add clean white silica to thicken the slag. It does not take much to do this, but it will hold the slag to the crucible and keep it out of your mold.
8. Have a steady hand. Quickly but steadily empty the crucible into the mold. Good tongs are essential.
9. If you want a mirror finish, have a fan flame set up over your molds. This disturbs the surface movement and organization into crystallites (or contraction patterns) and prevents oxides from appearing.
10. Put a bunch of paper towels or cotton rags in the bottom of your stainless quench bucket. When you dump your molds and the bars out and into the quench bucket, it'll keep them from getting dinged or marred.
To the pros: I have had success de-oxing silver with hydrogen or methane gas blown through it.
Lou
Jimmi
Well-known member
Thank you for the input Lou. I think holding it at a high temperature might be my primary culprit. It did start to boil as I removed the first torch and began to pour it. I think will give number 7 a try too. Sounds like a good idea. Ionly wish it was over 100 ounces in this bar though. Although I have over 1000 more ounces at least to do. And the person I'm doing this for has stated that he would like some larger than 10 ounce bars now as well. 
Time to fire up the furnace I guess. Torch melting it all into ten ozt. bars seems like it would take too long . Again, thank you. You're always a big help. And Thank you, as well to everyone else in the forum as always for being such a big help to everyone who wants to keep learning and improving.
Time to fire up the furnace I guess. Torch melting it all into ten ozt. bars seems like it would take too long . Again, thank you. You're always a big help. And Thank you, as well to everyone else in the forum as always for being such a big help to everyone who wants to keep learning and improving.
