Melting silver cement - how to properly do it ?

[Wingedcloud]

Hello fellow refiners,

I'm calling for your precious help regarding silver cement melt.
I tried getting silver cement for the first time, and the process I used was pretty much straight forward:
- getting a solution of silver in nitric acid;
- cementing the silver out with copper,
- washing the cement with hot water 2 to 3 times (wasnt able to remove 100% of copper nitrate though, but read it wasnt much of a trouble);
- drying and collecting.

From here on, melting is the next step. Since i've never melted silver cement before, i searched for the proper method of doing it: Hoke states on page 79 (silver chapter) that "a flux containing borax with charcoal or sugar, in a graphite crucible" should be used. After further reading on page 317 (fluxes) I understood that sugar prevents oxides from forming on the silver, by removing oxygen, improving the purity of the melt.
I also saw samuel-a video on youtube on silver melting, where he states that heating the crucible before adding the silver is necessary. I have samuel-a and kadriver videos as a reference for my work, because I think they provide with good and accurate info on how to properly recover and refine.

My question is the following:
Should I heat the crucible together with the borax + sugar, or heat the crucible alone?
After heating, the silver cement and the flux should be added separately or is a pre-mix necessary and advisable?
Can the melt be done in a sand crucible, or the graphite crucible is a must?
I currently dont have anything to pour the melted silver into. Is that really necessary or it is possible to remove the silver from the crucible after is cools like we do with relatively small gold buttons?

I am sorry for the long post and lots of questions, but couldnt find proper guidelines for my doubts on the forum or the internet.
Hoping someone can help, i present my kind regards,
Winged

 

[Smack]

Regardless of what your pouring your melt into, it must be preheated to get rid of moisture to prevent a steam explosion. As for borax and sugar, it depends on what the end game is. If your going to further refine your silver in a cell I wouldn't use borax or sugar. Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake.

You can let your melt cool in what you've melted in if your vessel is of proper shape, meaning a shape that is usually tapered in a way as to not restrict the solidified metal from coming out freely. I use clay graphite crucibles for larger melts and a Fused Silica melting dish for smaller melts.

 

[goldsilverpro]

In a pinch, I've made quite a few molds out of angle iron. Unfortunately, I couldn't find a photo. It's just a short length of angle iron, which acts as a trough - I would slant-cut the ends a few degrees so the bars will easily slide out . Two equal-sized small steel plates are welded to the ends. These plates are of a size to completely cover the ends and act as legs, to hold the angle iron off the working surface about 1/2". No welder? - just clamp the whole thing together with a C-clamp or two (might take more than 2 hands). The bars will have a triangular cross-section. If you only have a small amount of silver, you can put something under one end and pour into the other end.

I've also seen those cast iron gizmos used for baking corn-ear-shaped pieces of cornbread used for molds.

Whether you're using steel or cast iron, you'll have to coat the inside of the pre-heated mold before pouring molten metal into it. When pre-heating, you don't have to get it red - you're only getting it hot enough to drive out any moisture. With an acetylene torch fired up with a small flame produced with acetylene only, no oxygen, you can apply a layer of carbon on the entire inside of the mold. Instead, you can brush on a thin coating of motor oil - no puddles. The hot silver will turn the oil to carbon. I knew one guy that sprayed on WD-40. You can also buy commercial mold coatings.

 

[anachronism]

If it helps I can confirm that WD-40 works perfectly.

 

[Wingedcloud]

Thank you Smack for you reply answering my questions. I'll just collect silver cement for the time being, before I can get something to pour the molten silver into.
The only thing you said and that I did not understand was this:
"Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake."

Would be much appreciated if you could clarify this.

Kind regards,
Winged

 

[upcyclist]

The only thing you said and that I did not understand was this:
"Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake."

Would be much appreciated if you could clarify this.

He's referring to pouring your molten metal into water, so that you end up with your metal in shot (or "cornflake") form. That way, you are processing a bag full of material with lots of surface area in your cell, as opposed to a monolithic bar with less surface area.

As with all shorthand references to the craft here, you are best served by searching the forum for more details (using ice, how to avoid losing your metal because it alloyed with your bucket, etc.).

 

[4metals]

I've made quite a few molds out of angle iron. Unfortunately, I couldn't find a photo. It's just a short length of angle iron, which acts as a trough - I would slant-cut the ends a few degrees so the bars will easily slide out . Two equal-sized small steel plates are welded to the ends. These plates are of a size to completely cover the ends and act as legs, to hold the angle iron off the working surface about 1/2"

This method is described by Loewen in his book. I never was able to get a satisfactory release of the bar even though I did make the angle as Chris described. I always welded the ends on.

No welder - just clamp the whole thing together with a C-clamp or two. The bars will have a triangular cross-section.

But this part is brilliant, a clamp would eliminate the need for welding and the ends come off to facilitate the release! I'd bet you don't even need the angle if the ends come off!

 

[Topher_osAUrus]

This method is described by Loewen in his book. I never was able to get a satisfactory release of the bar even though I did make the angle as Chris described. I always welded the ends on.

4metals, may i ask what you used to dress the mold? Soot, oil, wd-40? Maybe another clever means for carbon?

 

[4metals]

I always carbonized the mold with an acetylene torch which I only used for this purpose. Not oxy acetylene, just a "B" tank of acetylene and a hand torch. When I wanted soot I choked off the air intake to the torch by wrapping my fingers around the torch air intake, instant soot!

 

[goldsilverpro]

When I had my last refinery, I did a lot of silver. I cast 10 oz (5 at a time) and 100 oz (1 at a time) bars in graphite book molds. Even with graphite, I carboned the molds with acetylene - they always looked better than with bare graphite. I used 2 C-clamps to secure the top plate on the mold. Worked great.

 

[4metals]

Were your bars dead on with a book mold or did you sell by weight?

Today it seems customers want bars exactly 5 10 or whatever ounces.


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[goldsilverpro]

Were your bars dead on with a book mold or did you sell by weight?

Today it seems customers want bars exactly 5 10 or whatever ounces.


Sent from my iPhone using Tapatalk

Sounds like a lot of work to me

After cutting off the sprues (I had a big power bandsaw) and weighing the bars, I remelted them if they were under 10 or 100 oz (usually an air pocket - rare). Otherwise, I stamped a little under the actual weight in tr.oz, with 2 decimal places. I had no problem selling them for a fair premium. The sooted book molds gave a nice smooth surface with nice big crystals. And, of course, the pipe ends up in the sprue, which is cut off. What I hated was stamping them, one character at a time. I always lined up 100 of the 10 oz ones at a time, when I stamped them. Real idiot work. I think it took longer to stamp them than it did to cast them. I got pretty fast on the casting, once I was able to not miss the sprue holes.

 

[Wingedcloud]

The only thing you said and that I did not understand was this:
"Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake."

Would be much appreciated if you could clarify this.

He's referring to pouring your molten metal into water, so that you end up with your metal in shot (or "cornflake") form. That way, you are processing a bag full of material with lots of surface area in your cell, as opposed to a monolithic bar with less surface area.

As with all shorthand references to the craft here, you are best served by searching the forum for more details (using ice, how to avoid losing your metal because it alloyed with your bucket, etc.).

Thanks upcyclist, that clarifies it for sure
I don't have a silver cell yet, because never recovered or refined silver before. But after getting this little (but valuable) piece of information, i'll surely consider doing a pour shot for later refining

Winged

 

[goldsilverpro]

The only thing you said and that I did not understand was this:
"Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake."

Would be much appreciated if you could clarify this.

He's referring to pouring your molten metal into water, so that you end up with your metal in shot (or "cornflake") form. That way, you are processing a bag full of material with lots of surface area in your cell, as opposed to a monolithic bar with less surface area.

As with all shorthand references to the craft here, you are best served by searching the forum for more details (using ice, how to avoid losing your metal because it alloyed with your bucket, etc.).

Thanks upcyclist, that clarifies it for sure
I don't have a silver cell yet, because never recovered or refined silver before. But after getting this little (but valuable) piece of information, i'll surely consider doing a pour shot for later refining

Winged

Unless one is a real klutz, any silver coming out of a silver cell is at least 999 Fine and possibly 999.5 or even 999.9 Fine. At just 999, silver is considered PURE in commercial trade. The only purpose I can think for shotting pure silver or gold is to sell it to jewelers. Otherwise, for IMPURE silver or gold, the purpose of shotting is to increase the surface are so it will dissolve faster. With PURE silver, I would probably cast bars and sell them, unless you just want some BB's or cornflake to look at.

 

[Palladium]

I return all refined silver to my clients in crystal form. This saves me the trouble of all the melting, gas, and work. It also serves the purpose of a self assay or hallmark and it's divisible in almost any quantity you can want. Like Chris said: you would have to be a klutz to really screw it up.

 

[Lou]

Do you ever test its purity?

 

[Wingedcloud]

The only thing you said and that I did not understand was this:
"Furthermore, if you do intend on refining in a cell, you would be best served to pour shot or corn flake."

Would be much appreciated if you could clarify this.

He's referring to pouring your molten metal into water, so that you end up with your metal in shot (or "cornflake") form. That way, you are processing a bag full of material with lots of surface area in your cell, as opposed to a monolithic bar with less surface area.

As with all shorthand references to the craft here, you are best served by searching the forum for more details (using ice, how to avoid losing your metal because it alloyed with your bucket, etc.).

Thanks upcyclist, that clarifies it for sure
I don't have a silver cell yet, because never recovered or refined silver before. But after getting this little (but valuable) piece of information, i'll surely consider doing a pour shot for later refining

Winged

Unless one is a real klutz, any silver coming out of a silver cell is at least 999 Fine and possibly 999.5 or even 999.9 Fine. At just 999, silver is considered PURE in commercial trade. The only purpose I can think for shotting pure silver or gold is to sell it to jewelers. Otherwise, for IMPURE silver or gold, the purpose of shotting is to increase the surface are so it will dissolve faster. With PURE silver, I would probably cast bars and sell them, unless you just want some BB's or cornflake to look at.

I said i'll consider doing a pour shot, because, as far as I have learned, the purity of a melted cement silver bar is around 99 to 99,5%. So, to reach the accepted in commercial trade 999 purity, as you stated, I suppose (i've never done it) a silver cell is needed to improve the 995 to 999 (or higher).
That is why I said I would consider doing a pour shot of my melted cement silver, for when I have a silver cell. Please correct me if I am wrong.

Winged

 

[Lou]

It all depends on the contaminants.

In general, rinse cement silver with borax and nitre solution will produce 3N+ Ag that is unsuitable for minting due to high O.

Lou

 

[saadat68]

Can I melt silver cement without using borax ?
what happen If I don't use borax or any flux ? :shock:

 

[goldsilverpro]

You've probably already answered these. Are you using a torch and melting dish, an electric box furnace, a gas furnace that you load the crucible at the top, or what? If you're using a crucible, how big is it and what is it made of? How much silver cement do you have? How did you rinse the cement? Is it dry?