# Melting silver cement - how to properly do it ?



## Wingedcloud (Aug 13, 2016)

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


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## Smack (Aug 13, 2016)

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.


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## goldsilverpro (Aug 13, 2016)

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.


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## anachronism (Aug 13, 2016)

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


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## Wingedcloud (Aug 16, 2016)

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


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## upcyclist (Aug 16, 2016)

Wingedcloud said:


> 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.).


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## 4metals (Aug 16, 2016)

> 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!


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## Topher_osAUrus (Aug 16, 2016)

4metals said:


> 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?


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## 4metals (Aug 16, 2016)

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!


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## goldsilverpro (Aug 16, 2016)

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.


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## 4metals (Aug 16, 2016)

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


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## goldsilverpro (Aug 16, 2016)

4metals said:


> 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.
> 
> ...


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.


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## Wingedcloud (Aug 17, 2016)

upcyclist said:


> Wingedcloud said:
> 
> 
> > The only thing you said and that I did not understand was this:
> ...


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


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## goldsilverpro (Aug 17, 2016)

Wingedcloud said:


> upcyclist said:
> 
> 
> > Wingedcloud said:
> ...



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.


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## Palladium (Aug 18, 2016)

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.


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## Lou (Aug 18, 2016)

Do you ever test its purity?


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## Wingedcloud (Aug 18, 2016)

goldsilverpro said:


> Wingedcloud said:
> 
> 
> > upcyclist said:
> ...



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


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## Lou (Aug 18, 2016)

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


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## saadat68 (Aug 19, 2016)

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


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## goldsilverpro (Aug 19, 2016)

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?


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## Barren Realms 007 (Aug 19, 2016)

goldsilverpro said:


> 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?



I don't think he currently has any material but I could be wrong.


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## saadat68 (Aug 20, 2016)

goldsilverpro said:


> 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?


I am in learning. don't have any material. I want to know witch is better 

gas furnace or electric furnace ? 
using borax or don't use it 

in YouTube I see a person melt 1 KG dry cement without borax with torch and in another clip I see melt 0.5 KG silver chloride with borax in ceramic crucible with a torch


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## Lou (Aug 20, 2016)

If you are learning, you need to spend more time reading and less time asking questions that have been hashed out ad nauseum. I for one feel like a broken record half the time here.

The more you read and understand fundamental separation science, the more you'll look back and realize that there's no single process solution to every material but that knowing what does what (if not why) and when to use it will make this all.._easy-er_.


*
As for AgCl and borax...NO! Never melt AgCl ever unless you're painting glass with it. Don't let it get dry, even if you plan on solid state reaction with Na2CO3.*


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## butcher (Aug 20, 2016)

Great advice as alway's Lou.

There is no substitute for study, I still do not understand why someone thinks they can learn by asking a thousand questions when they will more easily learn a billion more answers by spending that same amount of time in study, and gain a much better overall understanding of the subject.

How is being a dad going? Have you been getting any sleep? Maybe that is why you seem somewhat cranky today. I bet she is growing like a little weed and more cute than a shiny gold button.

P.S. have you seen the new gold pregnancy test kits?


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## Lou (Aug 21, 2016)

butcher said:


> Great advice as alway's Lou.
> 
> There is no substitute for study, I still do not understand why someone thinks they can learn by asking a thousand questions when they will more easily learn a billion more answers by spending that same amount of time in study, and gain a much better overall understanding of the subject.
> 
> ...



It's awesome! Yes, she grows fast. And no, not much sleep.


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## Topher_osAUrus (Aug 21, 2016)

Lou said:


> butcher said:
> 
> 
> > Great advice as alway's Lou.
> ...



My boys didnt start sleeping through the night until they added meat to their diet. For desmond, that was a year old, for hendrix (who had a mouth full of teeth at 8 months) it was 8-9 months old.
...still dont get a full night sleep, but thats because of "scary ghosts and monsters"..


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## jason_recliner (Aug 21, 2016)

Topher_osAUrus said:


> ...still dont get a full night sleep, but thats because of "scary ghosts and monsters"..


Wait til you tell them about PGM salt and metastannic acid...


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## Topher_osAUrus (Aug 21, 2016)

jason_recliner said:


> Topher_osAUrus said:
> 
> 
> > ...still dont get a full night sleep, but thats because of "scary ghosts and monsters"..
> ...



Haha!

When i do, I will be sure to tell them about proper PPE's for pgm salts and sulfuric acid treatments for the metastannic as well... For every evil, there is a good


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## goldsilverpro (Aug 21, 2016)

I required 27, 3" X 9" impure cell bars (anodes) to fill the basket (about 29" x 29" square) of my 30 gallon Thum (horizontal) silver cell. When melting the impure silver in my top-loading gas crucible furnace, I used no borax. I cast the bars in preheated, then coated (usually brushed on motor oil - with no puddles) cast iron molds, whose inside bottoms measured about 3" X 9". I had 4 of these molds and then poured 4 bars, dumped them and brushed on a little more oil. I only poured enough silver in them to cover the bottom with enough metal so that it ended up in one piece and didn't separate - about 35 ounces per bar. If done continuously, preheating of the molds isn't necessary after the 1st pour - they're already hot enough. In the basket, the bars were all snugged together to maintain contact. If contact was lost on some bars during operation, I sprinkled some silver crystal in between them.

Without borax, you will end up with more BB's stuck to the inside walls of the crucible. I didn't worry about this since I knew that, eventually, I would get them. In my refinery, I had quite a few crucibles, and most I only used for a specific purpose. For example, I had 1 or 2 that were only used for pure silver and a couple only used for pure gold. When I used a torch and melting dishes for pure gold, nothing else was melted in them. When loading and unloading crucibles and for pouring, I only used charging tongs. With these, I could handle up to a #16 crucible safely. The only time I had problems was when the crucible had not been stored in a dry place. A couple of times, I tore off a chunk of the crucible with the tongs when I started to lift it. Do things slow and heat the crucible alone, slowly, before loading it. When I first started casting silver bars, I always started with the same weight of silver in the crucible. This cut a deep depression ring into the crucible, at the top surface of the melt (where oxygen is present, which ruined the $50 crucible. After that, I varied the amount of silver in the melt


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## Wingedcloud (Aug 21, 2016)

goldsilverpro said:


> 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?



I myself have low height round sand crucibles and a gas furnace, similar to the one in the picture.
I gonna melt my cement tomorrow. And since I still don't know if I should use borax, and the videos I've been watching don't make mention of using it, I'm just going to pre-heat my crucible, add some cement to it, and melt. When melted, I'm going to pour it into a pre-heated, oil coated mold I made with steel and see what happens...hope something good.

Winged


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## Lou (Aug 21, 2016)

Do use borax. Then add a small amount of sand to thicken it up. When I say "small" I mean like a pinch of salt of sand if you had added a tablespoon of borax. Little goes a long way.

At work, I use my broken borosilicate glassware for dirty melts.


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## saadat68 (Feb 6, 2017)

Hi
How much time is needed for melting silver cement in the furnace like this and using LPG or MAPP gas :
http://www.goldrefiningforum.com/phpBB3/download/file.php?id=33282&t=1


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## 4metals (Feb 7, 2017)

That is a nice little gas melter, once hot they will melt a crucible full of silver in 15 to 20 minutes. One thing to be aware of is when these are new, the refractory used to cast the furnace contains moisture which has to be removed by firing the furnace. It doesn't look wet but it has moisture. the first heat may take an hour to cure the refractory. After that it is much quicker to get to temperature. 
It is difficult to melt any metal until all of the moisture is gone as all of the heat goes to drying the refractory, can be frustrating if you don't realize what is happening. 

where did you purchase that furnace?


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## saadat68 (Feb 8, 2017)

4metals said:


> That is a nice little gas melter, once hot they will melt a crucible full of silver in 15 to 20 minutes. One thing to be aware of is when these are new, the refractory used to cast the furnace contains moisture which has to be removed by firing the furnace. It doesn't look wet but it has moisture. the first heat may take an hour to cure the refractory. After that it is much quicker to get to temperature.
> It is difficult to melt any metal until all of the moisture is gone as all of the heat goes to drying the refractory, can be frustrating if you don't realize what is happening.
> 
> where did you purchase that furnace?


Thanks
It is not my furnace. Look at first page  
But I make a furnace like this just smaller 8)


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## saadat68 (Sep 14, 2017)

Hi
I want to use my furnace for first time 
How much time need for heating the furnace and crucible to drive out moisture ?
What is the temperature? 
Before I read a post from 4metals about this but now I can't find that


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## butcher (Sep 14, 2017)

Crucibles do not take long to drive out moisture, they can be warmed and slowly brought up to red heat after a good warming.

Furnace refractory can be a different story, if it is a new furnace there can be a lot of moisture in its construction, some of the moisture is removed by allowing the refractory to cure in open air, before a low heat is applied, the low heat is run for as many hours or days (depending on refractory type and thickness). 
some may need days of curing and bringing heat to a certain value and holding that heat for a predetermined amount of time before raising heat to a higher value and another holding time. How the furnace refractory was made can be a major factor in how the furnace is cured, (blown in refractory cures faster than cast or poured refractory) before slowly raising temperature to red heat.

If the furnace refractory has been cured and fired before, the furnace in storage can absorb some moisture, which can easily be driven out with a short low heating period before warming up the furnace to red heat.

Curing really is dependent on the refractory material, and the moisture content of its construction, a fire brick and mortar furnace would not contain as much moisture and require less preheat, than a cast-able refractory with a surface refractory mud wall coating which would hold a lot of moisture in its cement type of construction.

How long it will take depends on how it is made and if it has ever been fired before or not.


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## saadat68 (Sep 14, 2017)

Thanks butcher
My furnace made from a firebrick wall like a cylinder (I bought that from shop) and mortar (I mixed cement and soil and perlite ) 
I made it 8 month ago! 
So I think 2 hour preheat in 400 or 500 centigrade is enough


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## butcher (Sep 14, 2017)

Just warm it up very slow, then bring the temperature to around 6oo degrees F. and hold it around there for the refractory to bake for a while.
Driving the moisture out slow is important, too much heat and the moisture inside will try to escape too fast, which can create small explosions of refractory as the moisture expands and has no place to escape fast enough.

The heat needs time to slowly drive the moisture out.


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## saadat68 (Sep 15, 2017)

Got it
Thanks


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