Can only get coral like silver crystals

[Nachocucu]

Hello everyone, my name is Ignacio, from Argentina. This is my first post here in the forum, but I have been reding and learning from it since a wile now. I have heard of it from, of course, sreetips aka Kadriver.

For the last 6 month I been trying and learning to refine silver by electrochemistry. My goal of the last month is to achieve large crystals. The type you can see from kadriver’s videos or posts here.
But, having tried several different configurations, I can only achieve this coral like formations with little variations. So, I am posting my experience to ask for your help. Have read several related posts here, watched every kadriver’s video and read other materials to. I am literally lost, and I have no idea what else to try.

Regarding current and voltage:
I have tried first whit the suggested 3 to 3,5 volts and let the current to set freely. When I did this, current was around 5-6 amps. Thinking that the current was to high to develop large crystals, I set a car light bulb as resistance (with low and high filaments). Whit this I lowered the current to an average of 0,9 amps whit 3 to 3,5 volts, the results was a more separated slow growing crystals but whit the same formation. I tried whit even lower current, around 0,2 amps for 3 volts. I tried with really low voltage and current, starting with 0,2 volts! But the result is always similar. The only particular difference I could notice is that the lower the current, the easiest the crystals fell from the cathod bowl. Whit only a slight tap to it the crystals fell down.

This is my configuration:

- Cathod: 1,5 liters stainless steel bowl

- Anode/anode basket: plastic container whit several holes all around it. My silver shot is now pure crystals because I have run my entire silver through the cell several times trying to improve.

- Filter: 2 layers of a cotton cloth. Works fine (I THINK), current can flow, and slimes cannot pass through. Tried to get the recommended muslin cloth but the kind found here is to bad and the slimes get through it. Couldn’t find any dacron as Kadriver use, nor nothing similar to it

- Electrolyte: 150gr of silver crystals per liter. Used distilled water to make it, then vacum filtered. Have done it 3 times thinking this is where I have failed. In the photos I am posting, you can see how clear it is because the “n” times I processed the silver through the cell. Photos are after running the cell 24hs.

- DC Power Supply: 20 volts; 10 amps, whit the in-line “car bulb” resistance

 

[Martijn]

In this post kurtak has some pictures of his silver cel. The one with nice fat terminated crystals seems to have a bit more pollution in it, and seems to be more than just copper looling at the color. Maybe that is a factor. The copper concectration can go quite high before ending up in the crystals.
https://goldrefiningforum.com/phpBB3/viewtopic.php?f=61&t=29270#p308540

Kurt, something to add? :?:

Martijn.

 

[Nachocucu]

Thank you Martijn! Kurtak achieved some impressive crystals.

I can see in his pictures that those crystals start very small and then turn into large ones. Could it be impatiens my problem? I am not sure because when I leave my cell working for several days/weeks only got a denser coral formation.

I am sure that copper in solution must make some difference, could that be the factor to grow big crystals? When I started whit silver shot from cement silver I saw no difference. If I want to add some copper in my electrolyte, would it be ok to add a couple of grams in the bottom of the anode basket?

Sorry for my Spanglish everyone. English, as refining, is not my strongest point.

 

[Martijn]

It's a well kept secret, but we'll find out. 8)
These crystals are worth more than just the silver weight to a collector.
I would like to have some on a nice stand to show.

I think the two last pictures are the same cell run, and the first is a different batch. Or later in the process.
Leaving them in longer would create thicker crystals i guess.
I would try lowering the voltage resulting in lower current. Play around with it. Try a setting and leave it there to see what happens. You can go on indefinitely removing crystals and just adding to the anode bag with this electrolyte since its so pure.

I got long thin branched crystals growing towards the anode bag that i had to knock down to prevent shortage.
Mine was in a SS bowl. His cell is in a jar with a cathode on the bottom, it seems. Can't see the distance between the top and bottom.
Current density/voltage level can be a factor.

Small differences create beautiful things. The conditions have to be just right though. That's why natural crystals are so rare.
Like some gems here on grf.

Martijn.

 

[kurtak]

The one with nice fat terminated crystals seems to have a bit more pollution in it, and seems to be more than just copper looling at the color. Maybe that is a factor.

Martijn.

Are you talking about the pic with the bigger crystal in the corner of the cell & where the electrolyte has a bit of a green tint to it ? --- if so that is probably because the anodes in that batch had a bit of Pd in them - &/or it could have just been bad lighting when I took the pic

If you are talking about the crystals outside the cell that is just flat out bad lighting when taking the pics

Kurt, something to add? :?:

As far I how I grow the larger crystals I don't have time to post how I run my cell right now but will - try - to post something if/when I get time

Kurt

 

[Nachocucu]

I would try lowering the voltage resulting in lower current. Play around with it. Try a setting and leave it there to see what happens. You can go on indefinitely removing crystals and just adding to the anode bag with this electrolyte since its so pure.

Current density/voltage level can be a factor.

This is what I’m doing right now, traying whit different Current density/voltage level. I will continue to post pictures and data as I go on.

What I do not understand completely is amperage or current density impact in the results. I know that amperage is a factor for deposition speed. Voltage is a factor of how the crystals forms, in which a lower voltage allows a slower and better crystal formation and a higher one makes quicker and branchy formation.

Is it like that? Again here is where it get confusing for me

 

[Martijn]

If the current is lower, there is more time to grow the crystals and maybe make them bigger and chunkier. I hope...

Current is a result of voltage and a resistance in a closed circuit.
The cell has a certain conductivity and thus resistance.
Applying a voltage to it, closes the circuit and a current starts flowing inversely proportional to the resistance the current encounters. The lower the resistance, the higher the current.
U=I×R
Every cell has different properties and dimensions resulting in a different specific resistance. Electrolyte concentration is a big factor too.
Lowering the voltage will result in a lower current.
Just find your voltage to achieve a certain desired current and wait for the results.

Setting a current limit prevents shortage damage to the cell.
Set it to just above your desired setting.
If your cell's resistance drops, the power supply will lower the voltage to match the current limit setting.

Martijn.

 

[Nachocucu]

Thank you Martijn very clear!

I have two question I would like to find an answer:

Why is 3-3.5 volts suggested as the best voltage to electrodeposit silver?

If I set the voltage say in 3,5 volts and change the current putting a resistance in line. What are the changes I should expect? Is it any good to do it? I have tried this and the only difference I can observe is a lower surface of the cathod being covered.

I will continue to search for info, I know for sure here in the forum are good answers

 

[FrugalRefiner]

3 to 3.5 volts is used in the silver cell because it is high enough to deposit silver at the cathode, but not high enough to deposit copper until the level of copper in the electrolyte gets too high.

There are many factors that affect the crystal structure of the silver deposits. Copper has already been mentioned. Some copper is desirable, but too much is not.

Surface area of the cathode vs. surface area of the anode is another. Temperature of the electrolyte, circulation of the electrolyte, distance between anode and cathode, other ions in solution in the electrolyte, and many other factors affect the deposit.

Unfortunately, I don't know that anyone has worked out the "perfect" conditions for large crystals. You'll need to keep experimenting to figure out what works for you.

Dave

 

[Nachocucu]

Thank you, Dave. You will see down this post I taken into consideration your advice.

So, I arrived home and the cell were as you can see in the following pictures. After about 30hs working at 0,3 volts/0,07 amp the crystals just grew to larger corals.

How crystals turn out

How it was when I unplugged it

After seeing this, I decided to start over to be able of showing you the progress. Also, I’ll incorporate some improves (I think) following all your advices and what I re-read in the forum.

After vacuum filtering my electrolyte, I added to it 20ml of copper nitrate (I save all my copper nitrate from previous refinings). Did this because my electrolyte was very pure since I’m re-processing only silver crystals. Also, added a couple of drops of 65% nitric acid. I know for a fact that my silver nitrate was depleted of acid because I always left some silver undissolved when I prepare it.

I lowered the anode height by 5 to 10mm into the electrolyte. Toke out the bulb resistance I had in line and restarted the cell.

I set it up for 0,2 volts. I will leave it like this for 24 hs and see from there. I’ll will update pictures after this. My idea is to increase the voltage slowly to see what changes in the cell, is the only parameter I will vary for now.

See how clear the electrolyte is after working 48hs

This is my vacuum system by the way. Really practical, reliable and easy to adjust

Adding copper Nitrate

How the electrolyte turn out afer adding the copper and nitric acid

How the power supply is set

and finally working

Nacho

 

[Martijn]

Putting a resistor in series with your cell will increase the total resistance of the circuit and lower the voltage over the cell and thus the current. The same effect can be achieved much easier by lowering the current setting to your desired setting on your power supply. The voltage will drop automatically.
A resistor will only generate heat and cause loss of energy.

Maybe if the current level has no effect, the AgNO3 concentration or the free HNO3 level has effect.
Lowering the cathode surface can be something else to try.
A stainless steel bowl has a much greater surface area compared to the anode basket. Big differences in anode-cathode surface can create depletion zones around an electrode.

A bottomplate can be made smaller and change the depletion zones in the electrolyte and .....heck, I don't know.... I'm just brainstorming here.

Will try it myself as soon as my power supply is done deplating silver flatware. I have only one unfortunately.
After that it's tied up with the copper refining cell. Busy busy 8)

 

[Nachocucu]

Putting a resistor in series with your cell will increase the total resistance of the circuit and lower the voltage over the cell and thus the current. The same effect can be achieved much easier by lowering the current setting to your desired setting on your power supply. The voltage will drop automatically.

What I was trying to do, is set a constant voltage in the power supply and drop the current by adding that resistance. You can see now that I took it out the voltage is set in 0,2 volts and current is 0,2 amps. When I have the resistance, I was able to set a much higher voltage and maintain the current low.

Lowering the cathode surface can be something else to try.
A stainless steel bowl has a much greater surface area compared to the anode basket. Big differences in anode-cathode surface can create depletion zones around an electrode.

I think the same. And for results I’m getting; I’m starting to think that this setup is just not right to try growing large crystals. The cell is running now with the parameters set last night and the results for now are being the same, I’ll post pictures after 24hs passed.

I would like to try a completely different setup: very small cathode area, big anode/cathode distance

Nacho

 

[kurtak]

I would like to try a completely different setup: very small cathode area, big anode/cathode distance

Nacho

You are starting to get the idea

You will NEVER grow large crystals in a SS bowl cell set up - the surface area of the cathode (the bowl) is WAY larger then the surface area of the anode

My cathode (the SS plate) is (about) three time bigger then the surface area of my anodes (my anodes are kilo bars & I can get 3 kilo bars in my anode basket)

For what it is worth - the "largest" crystals "always" grow out at the edges & the corners of the cathode

I run my cell set at 3 to 3.5 volts with the current limit set at 9.5 amps (it is a 10 amp power supply - so I set the current limit a bit under so the supply doesn't over draw on the current)

Sorry but that is all the time I have to post today

Kurt

 

[Martijn]

What I was trying to do, is set a constant voltage in the power supply and drop the current by adding that resistance. You can see now that I took it out the voltage is set in 0,2 volts and current is 0,2 amps. When I have the resistance, I was able to set a much higher voltage and maintain the current low.

That is because you are dividing the voltage over two loads. The voltage over the cel wiil remain the same with the same current.
U=U1+U2. and U=I×R. I is the same in the whole circuit.
That creates a power loss over the resistor.
Measure the voltage over the anode and cathode and you will see. The rest of the voltage is over the resistor.
Martijn.

 

[Nachocucu]

Has been a very busy day, but thanks to all your advices and the incredible amount of info inside this forum, I think I did a very good progress today.

I understood that I was going the wrong direction whit the concept of my setup. So, I tried to come up whit something that represent the best conditions possible for me at this time, applying what I have understood of all info shared with me, to grow large crystals.

Best recipient I have es this coffee jar that has a tall figure and square corners (something I seen favors growing big chunks.

I want to make a cathode that where as small as possible. Also, want to take advantage of the fact that larger crystals tend to form in the sides of the container. I did this cathode cutting a ss tube scrap that I had here, trimm about 3 mm thick. Then folded it to fit the sides of the jar and made a 90°-fold to connect it to a wire. I weld together the cable and the cathode whit tin and cover it al whit a thermoplastic tube that get smaller and tighter wen heated (sorry don’t know the name of it in English).

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I filtered again the electrolyte, would been better to make new to know for sure what is my concentration, but this only has been working for about 50hs at very low voltage. Also, processing almost copper-free material, is well enough for me. By the way the crystals where form the same way that before when I disassembled the cell, I post a picture.

Anode basket is something else I have reused, and I know the is much improvement to do. But I like the fact that it covers all the mouth of the jar so is no need for a lid. Electrolyte is up to the top of the jar, trying to use all the anode surface available (not much).

Set it at 1,5 volts, current set itself to 0,4 amps and has being running like this for around 7 hs now.
For lapses of 30 minutes I tried so rise the voltage and current, first to 2,5v, then to 3. But the grows look like too fast and long very thin crystal begun to grow. I change it back to 1,5v.

I refiled the anode whit silver shot, made from previous electrolyte precipitated on copper.

I know there is a ton of improvements to do, and I would really like if you share your thots about it. Beside this, I’m really happy whit how is turning out and the crystals are forming are better that my previous setup.

I wont be able to post tomorrow as I wont be here, I post again Friday afternoon.

Nacho

 

[Martijn]

Great idea to cut the cathode like that.
I missed kurt's comment about big ones always growing on the edges. Your's has a ot of free standing tall crystals all around. That way you don't need to deposit a lot of silver to get a couple of big crystals. Maybe a piece of stainless mesh 4 or less will do even better.

I could not resist to give it a try myself any longer.
Took a tall saucage jar and cut a cathode bottom plate with a long thin strip which I taped off.
There is more distance between the electrodes now. About 12 cm.
Started growing a layer of silver coral at 3 volt and then turned it down to 1.2 volts. Current dropped from 0.5 to 0.2 amps. The thin crystals get thicker and there are bigger shining surfaces showing every couple of hours.
They also don't seem to shoot up as much at this lower current.

Just turned it down to 1 volt. Current is stil flowing around 0.1 amps.
Can't wait for them to grow big and fat with some nice faceted crystals. Looking good so far. Anode bag is getting empty though... need more silver!
Busy dissolving scrap silver.
Man, this is fun! Thanks for starting this thread.

 

[Nachocucu]

Martijn, thanks a lot for joining in! you are making it much more fun and easier for me.

I think your crystals are looking great, much more than mine.

I have had no time to do a proper post about my progress but here is a summary, Ill try to do better and add pictures tomorrow.

I had the cell setup at 0,4 amps and things were going well. But all the larger crystals started to cover whit fine wooly-like crystals and the large ones stopped to grow at all. Again, only growing coral-like crystals. I’m clueless about why this happened.

Meanwhile, I read the tread “grow large silver crystals” one more time and I realized that no one seems to have tried the gelatin method someone mentioned. So, as things were already going south, I decided to give it a go. It made it a lot worst and add contamination to it.

I started all over, this time have set the cell the cell at 0,2 amps, about 1,1 volts. For 24 hs the cell only grew fluffy crystals and the few larger ones quickly covered whit thin ones. I have changed the parameters to 0,6 amps/2 volts and things started to go better (for now).

A couple of questions about your cell:

What is your electrolyte concentration? Mine is 150gr/liter
Is it new? Looks like have more come copper in it
Why did you started whit 3v and then drop it? Was it on purpose?

Thank you very much again
Nacho

 

[Martijn]

Hi Nacho. I tried the 3 volts first to stick to kurt's recipe.
I think it may in fact be needed to first create a skeleton for the bigger crystals to form.
I turned it down after seeing a layer of coral growing with fine needles.

My electrolyte: not sure.... sorry. I had a bottle of used light blue electrolyte from the stainless bowl cel. I added some pollution from a nitric digestion of slimes from the H2O silver deplating cell after cementing out the silver and from a nitric digestion to get more silver shot for the cell.
So this contains copper, nickel, and other impurities.
My supply of nitric is limited and i don't want to use too much to make new electrolyte every time.
Added no free nitric to it, but there could be some left in there from the last run.
And filling the cell the first time there was a bit silver chloride cloudiness. Maybe a drop of tap water got in some where. That settled quite fast.
When (IF) i get big crystals, i will determine the concentration of silver and free nitric by tritation and cementing of 100ml electrolyte. The pollution level will be more difficult to determine.

Gelatin: good to know it does not work for the silver cell.
It's used in the copper sulfate cell to smoothen out the deposited copper and make it more compact.

After seeing your cathode, i went and made this:



More edges :lol: lets see if this works.

Took the cell apart and restarted it for this new cathode. Even less surface than the last one. Same electrolyte used unfiltered.
I started the cell at 1 volt and left it over night to see if the start @ 3 volts is necessary.

Here's how it looks after 12 hours:

A light white layer and some crystals growing on the edges.
Hope they don't fall off some where down the line.

I my hurry starting up the previous cell i just dumped my jar of fine crystals in the anode bag, that's a nightmare to get out again.. went on to make shot from 'all the silver' :lol: i have, ran out of gas with the last ounce frozen stuck in the crucilbe!! And stores are closed due to a lockdown :evil:

The voltage and power consumption is so low, i'm thinking of making a small power supply for this cell from a 5 volt 1 amp cell phone adapter with a LM7801 voltage reducer in line to get it to 1 volts. Really simple and no big lab supply needed. Freeing my lab supply for other cells. My copper cell may work on this type of supply too.

I bet Kurt's having a blast reading how we're trying to figure it out :mrgreen:

To me, the journey is as much fun as the destination, if not more.

Martijn.

 

[Nachocucu]

I bet Kurt's having a blast reading how we're trying to figure it out :mrgreen:

I bet everyone that already walked this path is :lol: But I think the same as you, this journey is a lot of fun!
Your new cathode looks great. Can’t wait to see how it worked.

something that caught my attention is that, with my "ring cathode", the largest crystals grew in the middle of the jar, not on the sides. This makes me think that crystals grow larger where there is a lower current density within the electrolyte.


After restarting my cell, I was testing different voltages and amperes in 0.2 amp increments. from 0.2 to 1.2 amps, which was the amperage achieved with 3.5 volts. the best result was around 0.7 amps. However, the crystals did not grow very large and always tended to become covered with very fine crystals after a while.

how the cell turned out when i added gelatin it was only half a teaspoon

the
salvageable crystals from the first batch

Since I wasn't getting great results, I decided to try reversing the polarity for a few minutes. I read about this theory in another thread as well. The first thing I noticed is that the crystals almost immediately lost their luster and turned white. The finer crystals began to dissolve fairly quickly and the cathode surface was cleared of the smaller crystals. After a few minutes, I noticed that crystals were starting to form on the anode bag. I thought that with this I had ruined it and had pierced the bag, but when I disassembled the cell it did not seem to be the case. Anyway, I reversed the polarity again for a few minutes just to see what happened, but thinking that I had damaged the anode bag, I stopped the cell just a moment later when the crystals regained their brightness.

It is not very noticeable but that is how the white crystals were when I reversed the polarity

Crystals growing on the anode bag

the crystals that I liked the most from the second batch

I wanted to test the idea of making a cathode as small as possible, so I made one by cutting another strip of ss and covering everything until only a small point was exposed. I reset the cell with this cathode but it was a total failure. I tested amperes from 0.01 amps down to about 1.2 which was the maximum reached at 3.5 volts. In either case I could literally see silver hair grow and fall continuously. Very similar to what can be observed when we cement silver on copper, only with crystals as hair. Varying the amperage only changed the rate at which this happened.

Since a smaller cathode had given even worse results, I thought the next thing to try was a larger one. So again I cut and assembled a new cathode from the stube, this time in the shape of a circle, just the size necessary to fit through the mouth of the jar. As the cell had not been working for a long time since the last time I reset it, I only changed the cathodes, did not re-filter the electrolyte or remove the few crystals that had formed with the cathode in a point.
It is running at 2.75 volts and 0.75 amps, just starting.

The next thing to test will be a higher concentration of silver nitrate in the electrolyte.
Something that I would really like to try that is going around in my head is putting together a much bigger cell. between 4 and 5 liters. Kurt mentioned that his cell was quite large and I can recall someone mentioning someone else's cell that produced very large, massive crystals and that it was one gallon (I think it was Kurt as well). I have turned it over in my head and it seems logical that while the cell is bigger, so will the crystals. In nature, if you look at geodes for example, the bigger they are, the bigger the crystals they contain. I never saw a small geode with very large crystals inside. This experiment is going to have to wait because for now I don't have enough silver nor money to make 5 liters of electrolyte.

Nacho

 

[kurtak]

I bet Kurt's having a blast reading how we're trying to figure it out :mrgreen:

I bet everyone that already walked this path is :lol:

To be honest guys I am not sure I can tell you "how to" grow large crystals --- that's because I have never actually tried to "deliberately" grow large crystals --- they just happen when running my cell for the purpose of refining impure anodes to 9999 silver using the cell as the way to purify my silver & when I am done running the cell I just happen to end up with "some" crystals that are very solid ranging from 1 gram to as big as 6 grams with a lot more crystals that end up as nice solid "cubic crystal" structure that run from 1 gram down to a tenth of a gram along with a lot of fine to very fine crystals

So all I can do is tell you is how I set up & run my cell - why the larger crystals grow - I don't really have a clue

First of all the cell --- It holds 4 liters of electrolyte (so its about a 5 liter vessel) it measures about 5.75 X 9.5 inches inside (that's side to side - end to end measurements)

Cathode Plate is 8.25 X 5.25 inches = about 43.3 square inches

Anodes - I pour 1 kilo bars for my anodes & each kilo bar is about 4.125 X 1.5 inches = about 6.18 square inches per bar --- I can get 3 bars in the anode basket so about 18.5 square inches of anode - or with 2 bars in the anode basket about 12.25 square inches of anode

Electrolyte; - I dissolve about 500 grams of pure silver (I say about because I make sure there is NO free nitric left - so it could be a few grams more or less depending how the dissolving of the silver goes) the 500 grams of dissolved silver is then diluted to make up the 4 liters of electrolyte --- so that is about 125 grams of silver per liter of electrolyte --- which is about twice the recommended dissolved silver for running a cell as it was recommended to me by Harold & GSP when I first started doing this

The bottom of the anode basket is spaced about 4 - 4.5 inches from the cathode

When I first turn on the power supply volts are "set" 3.3 volts - My power supply has a max amp out put of 10 - so I set an amp limit of 9.5 - so the amps just run wild - up to the 9.5 limit

For about the first 24 hours I just let the power supply run at those settings as at those setting I have never had the crystal grow to the anodes causing the cell to short out --- after the first 24 hours - during the day I continue to run the cell at the above settings - but check on the cell every 2 -3 hours & knock the crystals down that are growing close (to shorting the cell) - then - at night I will turn the voltage on the cell to about 2 volts - this slows the growth down so that I don't need to worry about crystals growing to the anode & shorting the cell

In other words I run the cell at two different volt settings (after the first 24 hours) 3.3 volt during the day & 2 volts at night

Concerning the crystal growth --- as I said - the larger crystal ALWAYS grow out at the edges of the cathode - which in turn means finer crystals tend to grow in the center of the cathode directly under the anode basket

Lets see if I can explain it in a bit more detail - when the cell is first turned on - crystals "first' start to grow covering the entire cathode with a moss like carpet - after awhile you will see "some" spike like crystals "start" to form out at the edges while more moss like crystals continue to grow in the center --- as long as the (center) moss growth stays below the edge spike growth - the spikes will continue to grow in height & thickness --- at some point in the process - the center moss growth will also start growing spikes as well (spikes, feathers, ferns) heading towards the anodes & growing above the edge spike growth

So - if you keep that center growth knocked down below the edge growth - without disturbing the edge growth spikes - the edge growth spikes will continue to grow in size & density (or at lest some of them will)

There comes a point that the knocked down (or packed down) center growth builds up to the level of the edge growth so I start pulling (or racking) that center growth to the back of the cell (the end of the cell where the rod connecting the cathode to the power supply is) thereby allowing the edge growth crystals to grow in size & density

Keep in mind these are my results when running my cell to refine my silver to 9999 silver using the above method when running my cell - I have never "tried" to deliberately grow large crystals - they just happen when I do the above - the above is about a 4 day process

Sooooo --- now you guys can go to work on tweeking the above to see what you can come up with :mrgreen: :shock: :twisted: 8)

Kurt