# Pouring silver bars



## satosan (Feb 23, 2014)

I finally got some stuff together to pour some silver bars. I've been practicing remelting the same ingot to try to get a better pour going. I am starting with 1oz. bars and eventually maybe some bigger bars. I was searching last night how to remove the borax from the bars and any other pouring techniques. My setup is basic at the moment I bought a Smith little torch Prop/Oxy and have a rose bud tip with it too, ceramic melting dish(s), graphite molds. 
Last night after reading some on the borax issue I ended up throwing my bar in vinegar/salt solution overnight and in the morning most all was gone except a little piece stuck in an air hole. 
As you all know silver tends to solidify quickly. I see the mold should be preheated (which I do) but don't know if it is hot enough. It is all a work in progress. 
I am curious working on this small scale is it best to use a graphite mold or cast iron mold. Cast iron molds seem hard to come by and don't usually come in the size I may want.
Would preheating a graphite mold in the oven work better than torch heating a graphite mold?
Is there a point where too much heat could be used melting .999 silver shot with Prop/Oxy. Will the silver become oxidized at some point?
Should I run a richer oxygen flame during the melt or a more neutral flame?


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## Palladium (Feb 23, 2014)

Two things to look out for. The first is overheating. It take way less heat to melt silver than it does gold or copper. Overheating will lead to weight losses from the silver vaporizing off also. When silver is hot it has an affinity to absorb oxygen and as it cools the oxygen is all the sudden expelled from the surface of the silver and causes bubbles or pits in the surface of your bar. The mold being to hot with a combination of the oxygen escaping under the bar and trapped between the surface of the mold and the bar causes the bottom of the bar to raise up. You want the mold warm and dry, not glowing hot! Graphite is what i use. On the top surface of the bar where the oxygen is not trapped and escapes it causes pits or bubbles. When melting silver one should use a set of torches where the gas flow can be adjusted. You want an excess of propane and a shortage of oxygen so as you melt the silver there is no oxygen for the silver to adsorb. When you pour the bar keep the flame of the torch on the surface of the bar and this will lead to an oxygen restricted environment and a smoother pour. Once the surface skims you can remove the torch.﻿


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## MysticColby (Feb 27, 2014)

never use iron crucible for silver. you will get iron mixed into your silver.
for crucibles, I like clay-graphite and silicon carbide. silicon carbide is around twice as expensive, but supposed to last longer, also hard to get in smaller sizes (less than ~6 inch height).
for melting dishes, silica is a popular choice

you should not use so much borax that it is pouring out with the metal. especially with fairly pure metal, use just enough to coat the inside of the dish/crucible. you're not trying to cover the surface.


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## satosan (Feb 28, 2014)

Thanks for the replies. I seasoned the dishes before I first used them but haven't added any borax since. It will eventually all come together with some practice. Once I start melting shot it will probably be a little easier to work with than silver eagles and remelting them. I will try to use a more neutral flame less oxidized and see if that makes a difference. Maybe I'm just impatient and the cooler flame was taking too long (IMO) thus I would crank up the heat with O2.


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## niteliteone (Mar 1, 2014)

Just out of curiosity, 
Why would you want to destroy a self assaying form of pure silver to create a questionable content silver bar :?: 
In my opinion, you just lost money :shock:


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## justinhcase (Mar 1, 2014)

I have been using an iron mold for my anodes and finished silver bars.
They come out at about 70g each so use a home made charcoal and gas furnace and a large old fashioned hand made fire clay and graphite crucible that holds 200-300g at a time.
no one has ever complained about iron impurity.how much transfer are you lightly to get.
I save my good graphite molds and crucible's for finished gold as the price on silver is so low and that of factory graphite so high they would cancel out any profit I was lightly to make.
I did have a friend at Exeter university sneak a sample under there XRF which came back 99.99.they did drill into the sample before alignment so would that mean the impurity's are held on the outer layer much like oxidation on old bars??


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## butcher (Mar 1, 2014)

Iron will not amalgam with silver, (silver will not mix with iron in a melt), but iron will amalgam with gold.

Just my guess, I think silvers ability to dissolve and hold a lot of oxygen has something to do with this, the oxygen in the melt probably oxidizes the iron in the melt, which helps the iron oxides to report to the slag, but then this is just my guess at this point.

I believe it was Harold who spoke of a process where gold is removed from iron, using this principle, where silver has a greater affinity for gold than iron does, where silver can be used to pull the small amount of gold from the iron, (melting the gold-iron with more silver) the gold will report to the silver (leaving iron in the slag of the melt).

Elemental iron can also be melted with a salt of silver like silver sulfides, to reduce the sulfide to SO2 gases, forming an Iron sulfide layer (below the slag), below slag and the silver metal (here a cone mold is useful which can be a carbon sooted cast Iron cone mold.

Although I would not use an iron crucible to melt silver, when clay melting dishes or crucibles are so cheap, and if needed can hold up fairly well to fluxing. 

You can silver solder steel with a flux, although getting porous cast iron clean enough for the silver solder to stick to it is almost impossible, basically melting silver in iron or steel with a flux I would worry about soldering my silver to it. With a clay dish I do not worry about soldering the silver to the refractory dish (with a little flux like borax).
With a sooted (or oiled) cast iron mold the silver poured into it will not stick.

I would not worry about using iron for a mold for silver, although I would carbon soot the mold to help keep the silver from sticking to the mold.


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## bmgold2 (Mar 1, 2014)

niteliteone said:


> Just out of curiosity,
> Why would you want to destroy a self assaying form of pure silver to create a questionable content silver bar :?:
> In my opinion, you just lost money :shock:



I understand why someone would do that (especially with the cheaper silver). It's much easier to buy an ounce round or bar to practice melting or dissolving than it is to refine sterling silver or extract the silver from tiny electronic parts.

I wouldn't want to do it with something that had numismatic value but I've bought generic silver rounds and bars for spot price before. I've only ruined part of one of them but it was a good way to test my ability to melt and dissolve silver. I found out for myself that poorman's nitric will dissolve some silver but some is turned into something else. Probably silver sulfate??? I also tried some of the dissolved silver and a couple tiny .999 silver wires in a plastic propane bottle cap to see if I could make a crude silver cell. That also kind of worked but I ended up with silver sponge instead of the crystals or wires I was hoping for. That sponge did melt back into a bead but if doing this in a larger cell with impure silver, I expect it would easily be contaminated with any copper in the solution just because the deposited silver was like a sponge.

Someday I will either buy a little real nitric acid or come up with some type of distilling setup.

Anyway, that $20 or so piece of silver has provided many tests so far and I still have most of it. It's been a lot of fun for not a lot of money. Sure, I lost money doing this but I've gained experience.


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## satosan (Mar 1, 2014)

niteliteone said:


> Just out of curiosity,
> Why would you want to destroy a self assaying form of pure silver to create a questionable content silver bar :?:
> In my opinion, you just lost money :shock:



I was just practicing melting and pouring silver. Once I start pouring bars as a hobby I will use silver shot. I suppose some might say why would someone convert .925 silverware into .999 silver shot they just lost money.
There are plenty of fake ASE's and other silver coins/bullion so to say that an ASE is a self assaying form of pure silver is not 100% true anymore. I will say that this is not rampant at this point but I have seen enough examples of fake silver/gold coins/bullion in numismatic circles circles that my intent to pour my own silver bars is to be assured of purity. I have even witnessed numismatic PCGS graded coins that were faked in the holder. I will just have to source silver from a reputable dealer. I don't intend at this point to become a refiner although it is an interesting area of study. 
I didn't melt a ton of silver eagles, actually it was only 2 and I kept remelting and pouring it just for practice.
I am a coin collector too so I understand numismatic values and I don't highly prize AES's as they generally only sell at a couple dollars over spot and there about 300 million more to choose from.


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