Designing a DIY silver cell

[4metals]

A Thum cell requires a "candlestick", or some similar device to make electrical contact where Moebius anodes hang from a buss bar.

My idea of a candlestick is a fat anode with a 3/8” tapped hole that I thread an anode hook into. Just keep it on top of the anode pile.

A Moebius cell can usually output slightly higher purity.

I’d like to see some background to that statement. May be true, I haven’t seen it.

If it weren’t for the difficulty in scraping the cathode when it’s horizontal I would be saying Thum is the way to go. But it will take a concerted effort of the minds to figure that one out.

 

[Shark]

If it weren’t for the difficulty in scraping the cathode when it’s horizontal I would be saying Thum is the way to go. But it will take a concerted effort of the minds to figure that one out.

How much force would be needed to hit the bottom of the cell to break the growing crystal loose?
My thinking is plastic would be easier to get the impact right than metal, but I have nothing to base that on other than watching plastic react to impact with liquid in it. Of course crystal growth would be a big factor as well. Like a sonic cleaner maybe?
Would it disturb the slime's in the bag?

My idea of a candlestick is a fat anode with a 3/8” tapped hole that I thread an anode hook into. Just keep it on top of the anode pile.

I hang smaller copper anodes by doubling over the end of a heavy wire and hammering them tight in the drilled hole. They do come loose occasionally, but enough work to not need titanium screws or hooks. Hanging them from a buss bar as well.

 

[snoman701]

But outside of shops that are already ISO9001, what is the point of running a cell? Who wants product that isn't coming from a vetted source in any quantity that makes running a cell worthwhile.

 

[4metals]

Who wants product that isn't coming from a vetted source in any quantity that makes running a cell worthwhile

Because I’ve seen many systems from vetted sources, respected vetted sources, who don’t exactly have stellar customer service. We are not doing rocket science here. We may actually come up with a better mousetrap.

 

[snoman701]

I'm not talking about the system, I'm talking about the product, fine silver.

What are the actual advantages to making 999 silver? Your stamp doesn't mean much unless you are huge.

This can all be done really really cheap with off the shelf products...but the end result is 999 silver that you still can't move at a premium because you aren't a multimillion dollar corporation.

 

[orvi]

I'm not talking about the system, I'm talking about the product, fine silver.

What are the actual advantages to making 999 silver? Your stamp doesn't mean much unless you are huge.

This can all be done really really cheap with off the shelf products...but the end result is 999 silver that you still can't move at a premium because you aren't a multimillion dollar corporation.

Sometimes you find buyers like jewellers, who make his own alloys and need high purity silver without contaminants. And often they are willing to pay spot or above spot for it - as buying investment ingots can be more expensive.
Also, from fine silver, you can make silver compounds which could be sold as reagents for bigger companies or institutions. AgNO3 crystals, silver acetate, silver sulfate etc.

Not a huge volume can be pushed by this strategy, but it is a little sweet bonus for you if you can do this
I lived through the times, when I was paid 83% spot for silver, 999. Below 999, 80%... I do not want to fall into this again. Prices paid here are very bad generally, and without kilos and kilos... You barely make any profit doing silver. Unless you find other buyers, who are interested in the product with added value.

 

[Shark]

In my case sterling averages 80% of spot if small jewelry and 85% if larger items. If I can bring 99.9 the price goes to 96% with a very small minimum.

My main reason is learning, from some of the most knowledgeable people I know on the subject. Jump in and throw out some ideas.

 

[snoman701]

Not a huge volume can be pushed by this strategy, but it is a little sweet bonus for you if you can do this
I lived through the times, when I was paid 83% spot for silver, 999. Below 999, 80%... I do not want to fall into this again. Prices paid here are very bad generally, and without kilos and kilos... You barely make any profit doing silver. Unless you find other buyers, who are interested in the product with added value.

That's just it, the volume sucks. And yes, price on silver sucks. I get 92% on small amounts, and my buyer will complain that he's not making any money. If I take him 1000 oz he still won't pay on gold, and he'll up it to 93%. Obviously there are better buyers out there, but the difference between 93 and 95 is only $382 right now. That's not worth going out of state to witness a melt. The silver market on high % silver products isn't even close to what it used to be. Grandma's flatware was sold years ago.

The current premiums on physical silver are high, but they are high because that's the cost of business on the other end.

Anyway, the way I figured I'd set it up are Tamco tanks. I'd use a pool skimmer basket to hold the anodes, and have it nest into a hole cut in a sheet of plastic big enough to cover the entirety of the tank, and rest on the rim (or a painted plywood frame if the tank isn't sturdy enough). The sheet of plastic would have two other holes in it, one for your cathode connection and one for a piece of stainless tubing. The stainless tubing is used to siphon the tank empty. No holes cut in the tank. They are stress risers and that's where your tank will start leaking. Once empty, you just pick the tank up and dump it into a large collander or other draining vessel. Home Depot cement mixing tubs are the backbone of any small refining operation. Anyway, the tank empties into a 15 gallon drum by gravity via a siphon. Once you clean everything out you put your top back on and lift the 15 gallon drum high enough that the electrolyte will siphon back in. No pumps to break. The whole thing is controlled via a Sorensen 12v50a power supply. Depending on the tamco tank, you can set it up either Moebius or Thum style. On top of your sheet of plastic that is holding your anode basket, you place an inverted rubbermaid container that is hooked up to negative pressure exhaust. This will minimize your need for high room turnover air flow.

 

[Shark]

That's just it, the volume sucks. And yes, price on silver sucks. I get 92% on small amounts, and my buyer will complain that he's not making any money. If I take him 1000 oz he still won't pay on gold, and he'll up it to 93%. Obviously there are better buyers out there, but the difference between 93 and 95 is only $382 right now. That's not worth going out of state to witness a melt. The silver market on high % silver products isn't even close to what it used to be. Grandma's flatware was sold years ago.

The current premiums on physical silver are high, but they are high because that's the cost of business on the other end.

Anyway, the way I figured I'd set it up are Tamco tanks. I'd use a pool skimmer basket to hold the anodes, and have it nest into a hole cut in a sheet of plastic big enough to cover the entirety of the tank, and rest on the rim (or a painted plywood frame if the tank isn't sturdy enough). The sheet of plastic would have two other holes in it, one for your cathode connection and one for a piece of stainless tubing. The stainless tubing is used to siphon the tank empty. No holes cut in the tank. They are stress risers and that's where your tank will start leaking. Once empty, you just pick the tank up and dump it into a large collander or other draining vessel. Home Depot cement mixing tubs are the backbone of any small refining operation. Anyway, the tank empties into a 15 gallon drum by gravity via a siphon. Once you clean everything out you put your top back on and lift the 15 gallon drum high enough that the electrolyte will siphon back in. No pumps to break. The whole thing is controlled via a Sorensen 12v50a power supply. Depending on the tamco tank, you can set it up either Moebius or Thum style. On top of your sheet of plastic that is holding your anode basket, you place an inverted rubbermaid container that is hooked up to negative pressure exhaust. This will minimize your need for high room turnover air flow.

Beat me to it

 

[4metals]

What are the actual advantages to making 999 silver? Your stamp doesn't mean much unless you are huge.

There is still money in sterling silver refining, even if you don't make it into fancy bars with a recognized logo on them to sell for big premiums.

Take a small refiner wh buys in sterling for 10% under the fix. These are the guys most small town jewelers go to to sell their scrap. With a setup to produce 3000 oz a week, which is easily run and maintained by 1 employee. (including the daily titration) That puts labor for the silver refining guy (or gal) at $1000 a week on average.

Sterling typically contains half an ounce of gold for every 1000 ounces. Refiners don't pay on that gold because......... well they don't!

Processing enough sterling to yield 3000 ounces, about 3,250 ounces and refining it in house will allow them to save the 2% refining fee so in addition to the 8% they kept even when they shipped it out, they get to keep (at $19 silver) $ 1,142. They will also recover the gold from the slimes so add in another 1.5 ounces of gold ($1750/oz) or $2625. This makes a margin of $3767 before chemical costs and labor.

As far as selling your silver, there are lots of the IKoi bar-making machines being sold to people who do not refine, they just make bars on silver they buy. And make a nice premium. And silver bars are hot today, hotter than the silver supply. I know a few refiners that supply 1000 ounce bars to these guys for 10 to 15¢ under because it's hard to get silver to meet the demand today.

So you don't need the big name to sell your silver and you can make it work profitably. Just another line of income for a versatile refiner.

 

[4metals]

This style still needs you to manually push the silver needles off the shelf to fall into the easily lifted out basket. The down side is the scraping every 4 hours or so. no getting around that. This is the basket for the anodes.

A piece of PVC angle the length of the sides on the long side of the tank will allow this to be slid forward and make room to push the silver off the cathode and let it fall into the basket, then just slide it back and power up again.

 

[4metals]

How much force would be needed to hit the bottom of the cell to break the growing crystal loose?

They snap off from the cathode and never, or rarely, peel off clean. so some silver is always on the plate. That never seems to be an issue with a Moebius cell but with a Thum cell being horizontal I think a scraper may bind up.

Like a sonic cleaner maybe?
Would it disturb the slime's in the bag?

I do not know if ultrasonic vibration would loosen the crystals but it may also get the slimes dancing around in the anode compartment and likely cause them to work through the bags.......not good!

 

[Shark]

Wouldn’t this need welding or can they be bought in this shape at a reasonable price?

If the anode basket is slid out of the way, could the cathode be lifted high enough and safely, to dump the silver into the lower basket?

Maybe with the right cathode rocker?

Would need to be narrow enough to clear the angle resting area.
Would need to be sure the basket moves far enough to clear the cathode when raised.

 

[4metals]

View attachment 7C3BC788-DE11-479E-98DA-1110D82B4EB3.mov
This is a photo of a moebius cell cathode rocker on a single cell of a larger system. The newer systems use a round arm dropping down to dislodge the needles but it is the same principle.

The mechanics of breaking the needles off on a vertical system is gravity is on their side. The needles break off and drop so the scraping arm is never "snowplowing" a pile of crystals. Plus, without a large drive wheel the arms move back and forth about 8", enough for 2 (in this case) downarms to scrape the entire length.

With a horizontal plate you would need to cover the entire length in a single stroke with a plow to move the crystals off the end. I do not know how much resistance a pile would put up over time because, even on a vertical system, eventually the plates need a little manual scraping help. So while a plow may perform great on a clean smooth cathode, once it is roughed up by firmly anchored crystals, it may, or likely will, inhibit the plowing.

I think the mechanics of lifting the cathode to make an incline and then scraping it would present more of a challenge because now, instead of having a scraping component, you also need a co-ordinated lifting component. Manually scraping once every 4 hours isn't hard to do, but having to do it makes your cell only producing for an 8 hour shift.

I know one shop that has his rectifier on a timer for 4 hours to shut down. It allows scraping every 4 hours without worry of shorts from missing a scrape. He scrapes the cell first thing in the morning, 4 hours later, another 4 hours later, and first thing in the morning because the cycle allows it to run 4 hours when no one is there before shutting off. This effectively makes it work a 12 hour day. Still foregoing 12 hours a day and weekends. While this is more efficient than just 8 hours a day it is still 35% of what it could produce if it ran 24/7.

 

[Shark]

With that setup the angle of the bottom and the catch basin to the side makes a lot more sense. That cathode rocker is more advanced than what I was thinking. I like it.

 

[snoman701]

You guys are thinking too hard.

I used a piece of stainless steel expanded metal as the cathode. The "scrape" in this case need not actually scrape it, just knock off the needles. They then fall to the bottom of the tank. In my case, I wasn't even scraping, just tap tap with a hard metal object.

Every few days I'd pull the cathode and soak in nitric to clean it up, effectively making new electrolyte.

 

[Shark]

Waiting for others to pitch in.

 

[markscomp]

Waiting for others to pitch in.

still looking for cost analysis of a larger - (than a home set up)- of the cell - something that a normal 200 amp service can handle (or two 200 amp service combined) can create - managerial accounting number with an average cost per 1 amp broken into final tally of a 1 toz silver We do not do chemicals nor will we do fire anything. But a small-scale analysis may be beneficial to all

{ sorry ....... edit to really mean that we acquire things and resell or then tear down material {not shred - yet] and then have material sent out to United States refiners - sorry - Kind of like silversaddle does} Mark

 

[Shark]

That one is over my head. Also, it is one of the things I need to learn as well. For me to run a silver cell using 30 or more amps at this time, I either drop a copper cell or look into some serious rewiring. The next step would be a larger building with better power, not tied my current power at home. I am still in the hobby phase now, but there is opportunity to grow, I just have to decide which way I am going yet.

 

[snoman701]

It's minimal cost for silver. Copper the cost of electricity starts to add up.

It's a lot of current, but a low voltage, so the actual power utilization is small.