Advanced questions re Silver Refining - Please Help

[Alondro]

Dear all,
i've tweaked and tuned my process to my satisfaction. Initial loss % were skewed because of material that was not sterling, but likely plated brass, i tried the sugar and lye method, but it becomes literally sticky (pun intended, lots of sugar residue to wash away) , cementing on copper works best i realized when the concentration of the dissolved metals in solution is high, and when a little nitric is still present in the solution. Silver gets knocked off in copious amounts, until the dark green solution has turned light blue. Testing with drops of HCl if any silver remained in the solution > no AgCl dropping (no white streaks or clumps forming) . I noticed that the best way to get rid of copper that might have flaked by cementing, is after draining the remaining Copper Nitrate solution ( i don't process this , too cumbersome to recover nitric acid from it, and Cupric Nitrate crystals are not worth the effort i think ) , anyway by adding a little bit of my Silver Cell spent electrolyte (which still has Silver Nitrate in it) and vigorously mixing the cement, the remaining copper goes into the solution and the remaining silver of the electrolyte cements out as well. Leaving me with after rinsing and washing a very nice , shiny, almost white Silver powder. Then i melt the powder into bars for the silver cell. These bars are already 99% pure. ( tested with the Sigma precious metal verifier, on 99.9% setting the indicator almost falls into the brackets , which indicates were close to 99.9% )
Then i run the bars as anodes in a stainless steel bowl.

here comes my question, i do not care about size or beauty of crystal growth as i want to pour the final product into bars again.
I've been testing various batches varying, a) concentration of electrolyte b) purity of electrolyte (+/- copper contamination) c) varying voltage/amperage
As you can see from the pictures, i get results ranging from foil like flakes, to wool like clumps, to nice tree crystals , to small hard crystals.
To be honest i have not still figured out what influences what , regarding crystal growth, I have looked up the forum and youtube on this but it's not conclusive and clear.

So , my question is. What is best to obtain the purest (not nicest) form of crystals to melt into bars?
Correct me if i'm wrong:
a) low voltage and low current
b) high concentration of electrolyte
c) low contamination by copper

So far i'm working with a 6 inch diameter stainless steel bowl , the anode is placed in the middle, held up with a plastic coffe filter ( with 3 layers of coffe filter paper that i change and discard every 8h with the black slimes that accumulate ) using only poured bars (no shot ) as anodes.
Current is around 2A to 3A , Voltage from 1.1V to 3V ( depends on Electrolyte concentration and size of anode bars )

Clarification on parameters to use and how they influence crystal growth would be greatly appreciated, and i believe many in this forum are seeking similar answers.

( p.s. also is it possible to run 2 cells in series or parallel with one power supply? )

And also another question, any tips on how to prevent ( when pouring the silver into graphite molds ) the layering gaps of the silver bar?
I am blasting the graphite mold with a propane torch while pouring to eliminate the oxygen , but still i do get either little bubble holes or layer line on the bar side . (i'd like to pour an almost perfect bar) Any tops on that? See last pic for how the bars look like now (granted i poured them quick and dirty as i use them as anodes first , not for beauty. But still, knowing how to pour them as perfect as possible , TIPS appreciated )


Thank You in advance.

Instead of regular sugar, use cheap high-fructose corn syrup. I've done several ounces, one once at a time, by this method to toy with the conditions, and found that you can have several inches of water on top of the silver oxide after the lye step, then just pour the syrup in and let it react, giving it a slow stir. After all the silver is reduced, the syrup is mostly dissolved. It's then much easier to wash away.

You can also directly smelt down the silver oxide if you have the setup for it (this is recommended for large batches). Adding a little powdered carbon (graphite powder or very clean charcoal, the simple pellet type used for aquarium filters works fine) helps. Mostly, the carbon will help eat up oxygen dissolved in the silver (bubbling out as CO2), and thereby cut down a little on sprouts. In proper smelts, silver oxide will decompose completely into silver above 280C (536F). A simple wood fired kiln is more than enough to do the job, and saves money on expensive propane.

Just make sure to wash the silver oxide several times in distilled water, then dry before smelting. I don't believe a flux is needed at all, though perhaps a particular flux mix to float over the surface of the molten silver could also diminish the amount of oxygen dissolving in the metal.

Others who have more experience with smelting significant quantities of silver will know.

 

[user 69385]

Update. I decided to put a heating fan next to the Stainless Steel bowl. That allowed me to reduce Voltage to 1V and increase Amperage at 3 A.
Now i'm able to literally peel the layer of silver off the stainless steel bowl , like aluminum foil, also crystal growth is much faster.
Any comments? Explanations? i'm testing in the blind, i greatly would appreciate input on which variables affect crystal growth and how.
Thank You.

Not a hot plate? Warming platters are really cheap at thrift stores also. More of a direct transfer of heat. Of course, I am a noob, so can only talk from how I dry meteorites after cutting them

 

[billgold]

Dear all,
i've tweaked and tuned my process to my satisfaction. Initial loss % were skewed because of material that was not sterling, but likely plated brass, i tried the sugar and lye method, but it becomes literally sticky (pun intended, lots of sugar residue to wash away) , cementing on copper works best i realized when the concentration of the dissolved metals in solution is high, and when a little nitric is still present in the solution. Silver gets knocked off in copious amounts, until the dark green solution has turned light blue. Testing with drops of HCl if any silver remained in the solution > no AgCl dropping (no white streaks or clumps forming) . I noticed that the best way to get rid of copper that might have flaked by cementing, is after draining the remaining Copper Nitrate solution ( i don't process this , too cumbersome to recover nitric acid from it, and Cupric Nitrate crystals are not worth the effort i think ) , anyway by adding a little bit of my Silver Cell spent electrolyte (which still has Silver Nitrate in it) and vigorously mixing the cement, the remaining copper goes into the solution and the remaining silver of the electrolyte cements out as well. Leaving me with after rinsing and washing a very nice , shiny, almost white Silver powder. Then i melt the powder into bars for the silver cell. These bars are already 99% pure. ( tested with the Sigma precious metal verifier, on 99.9% setting the indicator almost falls into the brackets , which indicates were close to 99.9% )
Then i run the bars as anodes in a stainless steel bowl.

here comes my question, i do not care about size or beauty of crystal growth as i want to pour the final product into bars again.
I've been testing various batches varying, a) concentration of electrolyte b) purity of electrolyte (+/- copper contamination) c) varying voltage/amperage
As you can see from the pictures, i get results ranging from foil like flakes, to wool like clumps, to nice tree crystals , to small hard crystals.
To be honest i have not still figured out what influences what , regarding crystal growth, I have looked up the forum and youtube on this but it's not conclusive and clear.

So , my question is. What is best to obtain the purest (not nicest) form of crystals to melt into bars?
Correct me if i'm wrong:
a) low voltage and low current
b) high concentration of electrolyte
c) low contamination by copper

So far i'm working with a 6 inch diameter stainless steel bowl , the anode is placed in the middle, held up with a plastic coffe filter ( with 3 layers of coffe filter paper that i change and discard every 8h with the black slimes that accumulate ) using only poured bars (no shot ) as anodes.
Current is around 2A to 3A , Voltage from 1.1V to 3V ( depends on Electrolyte concentration and size of anode bars )

Clarification on parameters to use and how they influence crystal growth would be greatly appreciated, and i believe many in this forum are seeking similar answers.

( p.s. also is it possible to run 2 cells in series or parallel with one power supply? )

And also another question, any tips on how to prevent ( when pouring the silver into graphite molds ) the layering gaps of the silver bar?
I am blasting the graphite mold with a propane torch while pouring to eliminate the oxygen , but still i do get either little bubble holes or layer line on the bar side . (i'd like to pour an almost perfect bar) Any tops on that? See last pic for how the bars look like now (granted i poured them quick and dirty as i use them as anodes first , not for beauty. But still, knowing how to pour them as perfect as possible , TIPS appreciated )


Thank You in advance.

I am not an expert on silver purification, so take my comments for what they may be worth. Sreetips covers the subject quite thoroughly in his many silver processing videos.

You need 3.5 volts potential - use a constant voltage supply. The reason your currents are so high is partly due to the small size of your cathode bowl.

Sreetips says that sterling is too high in copper to make a good electrofining electrolyte, he says all that copper in solution means the solution becomes fouled too quickly. With his setup, he produces two approximately 1.5 kg lots of fined silver with each pure silver nitrate electrolyte change. He uses fine silver to make up his electrolyte.

Yes, if your supply can handle it, you can run cells in parallel. According to Hoke, the large commercial sites used to run many plates in parallel. Do not run them in series - the voltage drops would not be the same and all sorts of problems could occur.

Your silver bars look like they contain contamination. They also appear to have been too cold - or cooled too quickly. Are you preheating the mold? It is hard to avoid oxygen eruptions when pouring - as it does not come out of the liquid silver until it starts to cool. You can minimize the absorption by making sure you are using a reducing flame for melting. You could avoid most of the oxygen problem if you used an induction furnace to heat the silver crucible, but they are expensive. There might also be some sort of fancy setup that uses a shield gas to keep outside oxygen away from the melt.

Even Sreetips pours his bars with molds that are not hot enough to avoid pour lines. But I think he likes pour lines to show they are hand poured.

 

[lazersteve]

Here's some good reads on silver bars:

Pouring Silver Bars

and

Hand Poured Bars

and

Graphite Molds

Steve

Click box above for an old forum thread related to pouring Ag bars.

Steve

 

[kurtak]

The contamination i was referring to is due to there being 2 metals in solution at the same time. Cementation removes the silver from the solution, but in a muddy form where all the moisture in the mud is copper nitrate. You have to be very thorough in rinsing, but you’ll never get it all out. Same with silver chloride. So the difference between the 2 processes is 2 extra steps for little to no difference results. And it should be noted that cementation isn’t fire and forget. The condition of the copper has to be monitored. When the copper begins to get thin it has to be be replaced. There shouldn’t be any flaking.

This is mis-information (not true information)

If you want read about why it is mis-information red what I have posted in this thread ---------

https://goldrefiningforum.com/threads/converting-925-scrap-silver-to-shot-for-my-anode-basket.33490/

 

[cejohnsonsr1]

Make shot from the mud produced by either method. Run each through an electrolytic cell in separate runs. Start with pure, clear electrolyte for both runs. Watch as the electrolyte turns blue, indicating that copper is being removed from the feedstock. Run until you have produced about a kilo of crystal. Cement the silver out of the used electrolyte on copper. After all of the silver is removed, what’s left is copper nitrate. Cement that out on iron and weigh it. It will be somewhere between 15 and 25 grams, depending on how thoroughly you rinsed. Regardless, it’s at least a little bit more than 1%. That’s 2 9s. Not 3. Not 4.