# Best Ball Mill Media for Plated Silver Removal



## Fever (Jan 6, 2011)

Hi Guys!

It's been a while since I've participated on the forum, but I have been gleaning knowledge in the shadows as a lurker! I have a question for those who may have input regarding the best abrasive media option for grinding Silver plated metals in my ball grinder. This is my plan: (1) Cut my Silver plated scrap into workable sizes that will fit in my 35Gal cylinder. (2) Add the best abrasive media in the best sizes (I figure a variety of small-medium to get in all the nooks and crannies). (3) Grind the materials until all of the plated Silver is abraded as a powder, and collect. (4) Use the Nitric technique to dissolve the silver/Copper values, and precipitate the Silver using Copper. (5) Recover the dissolved Copper from solution and fire into buttons (need advice here too). (6) Collect the Silver crystals, rinse thoroughly, and fire into buttons. (7) Re-activate the Nitric solution for continued use, or dispose of accordingly.

I am thinking that non-metallic media would work best, as there would be no metal contamination outside of the abraded target metals in the cylinder. I am leaning toward Zirconium-based abrasives, as they are extremely durable.

Anyone have some advice in this category? I know the recoveries from Plated materials is low, but I have access to a variety of cheap plated scrap.

Thanks very much in advance for any help you can give!

-Fever


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## rusty (Jan 6, 2011)

Zirconium good choice, rather than spend time cutting your scrap into little pieces why not buy or make a sandblasting cabinet and remove the silver plate. When blasting your media will cut faster by angling the nozzle to the work.

Direct hits are much slower to remove rust and paint so I would expect the same results removing silver.


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## Fever (Jan 7, 2011)

Thanks for the input Rusty. I thought about sandblast, but since I already have the ball mill, and plenty of time, I thought I'd go that route. I also think the powders will be easier to collect by just dumping out my cylinder, which is tapered, into a vessel for later use. I would think the sandblast method would encourage lots of particle dispersion all about the machine, and may prove difficult to remove entirely. But, both methods should produce similar results.

I agree on the Zirconium. It's not cheap, but I believe the initial costs will be offset by the abrasive's longevity.

Thanks,

Fever


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## nickvc (Jan 7, 2011)

This sounds very similar to the barrelling process used to finish jewellery mechanically.
The idea is to use different forms of media in the barrels to remove casting marks and blemishes down to a very high finish when a quick polish will finish the process. The process works well but the metallics are in very small particles and are usually recovered from settlement tanks along with big volumes of the media that's broken down during use. You might avoid that problem using zirconium but will I'm sure have some of the media grind down into your silver copper powders. If I remember correctly ceramic cones and coconut shell were some of the media used. Don't know if this helps but a quick google search might give you some further ideas on media and times taken. A point to remember is that though you have plenty of time your power isn't free to run your mill so do your maths before running for weeks and see if it really is worth it.


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## Fever (Jan 7, 2011)

Thanks for your advice nikvc,

As far as the time it will take to break down the Silver plating, I do not foresee this taking very long at all. Most Silver plate is quite sparse in thickness. But you are right, the process will consume electricity- a deduction I am willing to suffer through to obtain my powders =)


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## Barren Realms 007 (Jan 7, 2011)

nickvc said:


> This sounds very similar to the barrelling process used to finish jewellery mechanically.
> The idea is to use different forms of media in the barrels to remove casting marks and blemishes down to a very high finish when a quick polish will finish the process. The process works well but the metallics are in very small particles and are usually recovered from settlement tanks along with big volumes of the media that's broken down during use. You might avoid that problem using zirconium but will I'm sure have some of the media grind down into your silver copper powders. If I remember correctly ceramic cones and coconut shell were some of the media used. Don't know if this helps but a quick google search might give you some further ideas on media and times taken. A point to remember is that though you have plenty of time your power isn't free to run your mill so do your maths before running for weeks and see if it really is worth it.



Corn cob's for shure and I think pecan shells have also been used.


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## 4metals (Jan 7, 2011)

When I dealt with jewelers wastes a common material was walnut shells, they did a great job of polishing and obviously removed metal because they were payable as sweeps after they were incinerated. Extracting the values from the sweeps chemically will be an issue. Probably not profitable with silver at $30.

I agree with Rusty, sand blast, possibly with glass beads, and separate the media from the values with acid.


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## Fever (Jan 7, 2011)

All valid and acknowledged points, thanks guys.

Moving forward with my original formula. Here's a snapshot of the Zirconium Oxide media I will be using. I'm going to use the small 2mm spheres, which should gently grind the coatings without smashing the living hell out of the base metals.


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## goldsilverpro (Jan 7, 2011)

I tried this once with silicon carbide abrasive and all it did was get the parts dirty. I do think that, with the right media, it could work.


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## Ian_B (Jan 7, 2011)

I've been using green plastic triangles with silica for cleaning and polishing sterling silver after casting in a rotary tumbler
here is the exact media from the same site purchased from
http://www.contenti.com/products/tumbling/180-623.html

the tumbler is here http://www.contenti.com/products/tumbling/180-525.html

with the media about 1/2 filling drum, about 1/4 full of water maybe 1 tbsp of dish soap and about 400grams of sterling and it polishes it up quite nice after a couple hours

take the drum off let it settle over night and it leaves a nice cake of silver powder/media dust at the bottom 

I know it would be different with the plated items but just explaining my experiences with a tumbler with liquid not sure if that would be better then just media on its own allowing the silver plate layer become dust and get all over the place might be easier to collect the silver if it is in water because it would collect wherever the lowest spot is 

good luck and keep us posted


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## goldsilverpro (Jan 7, 2011)

You also must consider the separation of the removed silver from the media, which could be a problem. I would probably first try a media that is inert to nitric acid. That way, the Ag/Cu could be leached from the media. Your zirconium oxide might fit the bill.


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## Fever (Jan 7, 2011)

Thanks for the info guys!

GSP- What size/shape were the Silicon abrasives you used? How long did you tumble them to get the "dirty" result? I assume by that term you mean that the plating was not removed?

Ian- Yes, water always encourages the heavies to settle at the lowest points. Yet I think the way I am proposing this procedure (dry, no grit, just Zirconium Oxide balls and the Silver plated materials), it should result in an easily collectible dry powder comprised of Silver and small amounts of whatever base metals were beaten away from the original material. This mixture will dissolve readily in Nitric, after which the values can be precipitated.

I will keep everyone posted!

-Fever


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## Fever (Jan 7, 2011)

GSP- Yes, my thoughts exactly. Zirconium Oxide is incredibly strong stuff, totally non-porous, and should not break down in the least under these circumstances. That is precisely why I chose this particular abrasive. If it all goes according to plan, the powdered remains will be almost exclusively metal.


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## goldsilverpro (Jan 7, 2011)

> GSP- What size/shape were the Silicon abrasives you used? How long did you tumble them to get the "dirty" result? I assume by that term you mean that the plating was not removed?



I don't remember the grit size. I ran it several hours. The SiC was probably powder and thus too small. Silicon carbide is black and it coated the parts. That's what I meant by "dirty". I did it on gold plated pins and the gold was not removed.

Were it me, I would try to find a media that was sharp, irregular (to get in all the cracks and crevices), hard, heavy, and impervious to nitric. Size would be important. Also, I would guess that the media/parts ratio would be quite high. I would think a vibratory finisher would work better than a tumbler.


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## Barren Realms 007 (Jan 7, 2011)

4metals said:


> When I dealt with jewelers wastes a common material was walnut shells, they did a great job of polishing and obviously removed metal because they were payable as sweeps after they were incinerated. Extracting the values from the sweeps chemically will be an issue. Probably not profitable with silver at $30.
> 
> I agree with Rusty, sand blast, possibly with glass beads, and separate the media from the values with acid.



That's what it was walnut shells, not pecan shells.


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## qst42know (Jan 8, 2011)

Silicon carbide is hard and sharp but is friable. It readily fractures exposing fresh sharp edges. It's tendency to to embed in soft metals makes it useful for cutting the hardest metals with brass or copper tools.

Ceramic deburring media comes in a variety of shapes that should prove useful. 

http://www.kramerindustriesonline.com/tumbling-media/ceramic-media.htm

Finding the right grade is going to be the key. A polish grade will be to slow while an aggressive cut grade sheds worn abrasive that may embed in soft metals.


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## AuMINIMayhem (Jan 26, 2011)

goldsilverpro said:


> I tried this once with silicon carbide abrasive and all it did was get the parts dirty. I do think that, with the right media, it could work.




admittedly... I did the same in a vibratory deburring machine. what a mess! :roll:


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## Irons (Jan 26, 2011)

Here's some zirconia medium for sale on fleabay:

http://cgi.ebay.com/Zirconia-M-Grinding-Media-1-2-lot-5-/400187393813?pt=LH_DefaultDomain_0&hash=item5d2d070715

he has man lots listed


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## Fever (Jan 27, 2011)

UPDATE

I have been having great success in abrading and reclaiming the Silver plating in the ball mill! I re-tooled my process slightly, primarily in the type and size of grinding media I used. I decided against the Zirconium Oxide for the simple reason that round or quasi-spherical objects would not penetrate all of the nooks and small spaces in the target materials. I switched to an Aluminum Oxide media called Duramedia XC, in a small cylindrical shape with 30 degree angled ends. This has proven to be very efficient at removing the plating. I tumble the objects for about 4 hours to insure all of the plating is removed, then I empty the ball mill into a classifier screen placed over my gold prospecting pan.






I then spray the individual object down with water to remove the silver sludge, and it collects in the pan.




After rinsing all of the items and the media itself, I add the washed media and a fresh batch of plated items, and start the process again. I let the collected Silver sludge/water solution settle for 24 hours, then I pour off the contents into a jar for drying. This sludge/water is likely primarily Silver, but it will undoubtedly also contain smaller amounts of various base metals and bits of media as well. Neither should pose a problem when digesting the dried powders in Nitric, and any ceramic media particles left in the mix will be filtered out appropriately. I posted a few pics below, the last being the ongoing collected result of continued batches.




- Fever


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## lazersteve (Jan 27, 2011)

What do the stripped items look like after they have been processed?

Steve


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## Fever (Jan 27, 2011)

Steve-

The abraded items come out of the ball mill displaying their typical base metal colors. There are Brass and Copper items, some Steel, as well as lots of Zinc items. In the case of vintage plated silverware, I believe many of these are alloys of Zinc and other non-ferrous metals that make for a good "white" base metal upon which the Silver is plated. I've also noticed that many of the Copper and Brass stuff is first plated with Zinc, then followed with a final Silver plate. That way, the Silver is being applied to a "white" metal surface, upon which thinner plating can be achieved while maintaining an economic luster. Just a guess. It may also be to inhibit corrosion or oxidation of the base metals. I will only tumble these Zinc plated items until the Silver layer has been removed. No sense in continuing to abrade additional volumes of Zinc and other base metals. It's quite easy to determine visually when you have exhausted the Silver plate layers and have only the Zinc plating remaining. 

-Fever


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## nickvc (Jan 28, 2011)

Fever I'm pleased this working out as we have had many people try to recover silver from plated wares and failed due to the cost. Well done!
I'm not 100% sure but I doubt that the white metal under the plating is zinc but more likely a nickel alloy ( German Silver ) , I'm sure GSP can give a definitive answer to that, he is after all our resident plating expert.


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## Harold_V (Jan 28, 2011)

I'm inclined to agree with you, Nick. I know nickel is the barrier of choice when plating pins and other electrical items. The presence of the nickel barrier prevents migration of the plating to the base metal. 

Yeah, I know, that sounds strange, but the phenomenon is well documented and has been known to exist with silver and gold for years. I believe Sir T.K. Rose discussed the issue in his book. 

Harold


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## ORCB (Jan 28, 2011)

Hi, I'm interested in physical processes to remove the silverplate, just as a thought experiment. I was reading some threads on here and GoldSilverPro said that it's basically impossible to do economically? How cheap can you get silverplate? If it's only a few cents of silver per square inch, could it ever be worth it, even if you could extract it for zero cost? I don't see how but I have very little experience in all of this.


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## Fever (Jan 28, 2011)

Thanks for the comments everyone!

As stated, Nickel, or an alloy of Nickel, is probably what we're looking at under the plating of most items. It makes sense.

As far as my costs associated with this process? First we must answer this question- What is an acceptable cost for allowing one to quench his/her thirst for precious metals recovery knowledge? I buy all of my plated Silver scrap from thrift stores and garage sales at rock bottom prices. Now, realistically, am I getting back in Silver values what I put into this process in dollars? Most likely not! But, this is something I enjoy doing, it relaxes me after a long day's toil, and that is priceless in itself. I do know one thing; this process seems to be working very well for me, and I believe I am recovering all of the Silver values on these plated items, in whatever amounts they will yield. It will be interesting to see how much pure Silver can be recovered after the digestion/precipitation chemistry is complete (I haven't begun this step yet). All I know is that it's working, I enjoy it, and the process is sound. 

I'll keep you all posted as things progress....

Fever


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## Sodbuster (Feb 21, 2011)

If you have a ball mill, make your own grinding media out of some of your old ceramic processors.
As GSP stated "I would try to find a media that was sharp, irregular (to get in all the cracks and crevices), hard, heavy, and impervious to nitric" 
Just a thought
Ray


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## nickvc (Feb 22, 2011)

Hi Fever just bumping this thread to see if you have any further updates on your progress?
If you could get starting weights of the plated articles and the final recovered silver it would at least give the members a good idea as to how practical this method is.
I know for you this is about learning but this sounds the best idea so far to recover silver from plated material and who knows you might just have found the method that works.


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## Fever (Feb 22, 2011)

So far, so good. I have been tumbling my plated items in about 3 pound batches, with about 10 pounds of abrasive media as a charge in the ball mill. The reason I don't tumble larger quantities isn't because of the limits of my ball mill (which can happily tumble up to 35 pounds of materials in any given batch), but because I have sheared many of the larger plated dishes and serving platters into strips that will fit through the 4-1/2" mouth of the tumbler. Because of the geometries of these items, they can group together like sheets while tumbling, reducing the exposed surface areas. I am experimenting with bending some of these materials into particular shapes that tend to stay more independent of each other, such as semi-circles. I'm happy with what's coming out of the mill upon completion of the tumbling cycle to this point. There is very little of the abrasive media (Aluminum Oxide "Duramedia XC") being fragmented during the process, and my yield of the fine metal powders and the obvious removal of all surface Silver indicates that I am reclaiming all of the plating on the target items. I am still accumulating the Silver in a glass vessel, and I anticipate doing the chemistry and mechanical separations soon. I have been slammed at work lately, so I'm not able to move forward as fast as I would have liked to. As you can see in the picture, there is roughly 2" of recovered metal particulate sludge in the bottom of my 5" diameter glass vessel. So I have retrieved a 2" X 5" disc-shaped quantity of material from roughly 15 pounds of Silver plated items. I do not tumble the items past the initial removal of the plating, so I am confident that the recovered metals are primarily Silver, with little base metal percentiles (again, to be determined after dissolving, filtering and cementing).


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## Lonnie (Feb 22, 2011)

It's been quite sometime since any post were updated on this process . I have half a coffee jar I tumbled off with a rock tumbler . Removing the silver was the easy part . 

I wasn't smart enough to get a medium that wouldn't mix in with the silver/copper I was tumbling . As a result I have a mess LOL . I can place just a pinch in a test tube and add very weak acid solution and I get a fizzing uproar . Better have a bottle to dump the test tube contints into handy . 

I did reciently try a pinch in the AP solution and it's showing promise . The home made nitric will not work because the reaction is to foamy . It just climbs out of the test tube . This was a weak solution also . If anyone ever got to the point of melting silver tumbled off I'd like to see something posted concerning the results . 

When I done this I figured I could just torch the stuff with copper and silver melting and my medium floating . That didn't quite work as planned and the medium gets hot and starts popping and splattering . I did see small silver balls melting and then running down through the rest of the stuff LOL . However you can't keep a torch on it long enough to melt it all because of the popping and splattering it will do . 

If you do try this dont use rock polishing types of grit LOL


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## FrugalEE (Feb 22, 2011)

Lonnie,

I enjoyed your story.

Did you try using water and gold panning like technique to separate the silver?

What is your rock tumbing material? Hopefully something a lot lighter than silver.

I'm doing small experiments recovering silver from mica caps and I'm finding out how sticky cemented silver is. Even getting it off brand new glass beaker is hard and it wants to dissappear into coffee filters.

FrugalEE


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## Drewbie (Feb 22, 2011)

Try experimenting with froth flotation.


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## Lonnie (Feb 22, 2011)

FrugalEE

No I have never tried that . To be honest I was just going to tumble it off and worry about getting it back when I had it all in a jar . Well as luck would have it I was in an accident where I recieved some serious burns so the stuff just set for a couple years . I just reciently cleaned out my tumbler I had going at the time . 

The panning might just work I did take about an inch of material and placed it in another coffee jar . Filled it to the brim with water and shook it good and set it down . It did seperate into 3 defined layers . 
I could be wrong but I think silvers on the bottom then copper and then my polishing grit. I've been meaning to take a spoon or something and carfully removing a layer at a time and try the torch again to see how it went . 

I think I'll give that a try here in a little bit . 

Lonnie

btw best of luck with what your trying also . I'm new to this myself so I understand how it can be trying to figure things out . 

These caps you mention do they have much silver in them ?? Reason I'm asking is I have a truck load of big electrical caps like the electric company uses . They full of oil and have layers of a silver looking foil seperated by what looks like thin sheets of plastic plus this mica stuff you mention . 

Thats where I get most of my interesting material I'd like to get identified . Government auctions and usually big electrical items full of copper ( I scrap for a living ) . I've saved lots of interesting material over the years and it's time to start trying to figure out what some of it is .


btw I have no idea what the medium was . Just some gray looking material made to polish rocks . I tried it with no grit but was getting no where . Adding the grit made it fast LOL a mess but a fast mess :shock:


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## Lonnie (Feb 22, 2011)

Drewbie

Try experimenting with froth flotation


I just tried searching for this froth flotation and as usual I get ( No suitable matches were found.) as a responce . Is their anything else I can search for ?? Thanks for the lead anyhow I'll google it if I have to and look into that . 

Thanks to you both for your suggestions . 

Lonnie


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## Drewbie (Feb 22, 2011)

http://en.wikipedia.org/wiki/Froth_flotation

http://www.chem.mtu.edu/chem_eng/faculty/kawatra/Flotation_Fundamentals.pdf

Enjoy.


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## FrugalEE (Feb 22, 2011)

Lonnie,

Some of those oil filled capacitors contain PCB oils which are considered today as a pretty bad health risk, but you probably already know that and probably can tell which ones contain PCBs and which don't. I don't think any of them contain anything of value and most people consider them a liability. The scrap yard I sell to is pretty careful not to get stuck with any of them or flourescant ballasts, either of which might contain PCBs. The foil you see is most likely just aluminum. I've never taken one apart, but I've certainly used them over the years and continue to keep a supply on hand.

Search the forum for the still active Silver Mica thread and you can get any idea how much silver they contain and how to get it out. 

I've seen a lot of different capacitor types over the years and most have no salvage value, the exceptions being mica, chip ceramics, or tantulum types. If you have something you want identified post a photo or describe it in a new capacitor thread and I or someone else will help you figure out what it is.

FrugalEE


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## Ian_B (Feb 23, 2011)

are you guys using water in the tumblers as well as your medium?


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## Fever (Feb 23, 2011)

> are you guys using water in the tumblers as well as your medium?



YES


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## Lonnie (Feb 23, 2011)

Ian_B

Yes I did plus a drop or two of dawn dish detergent sure helps keep the black grimy stuff cut loose . 


FrugalEE

I couldn't tell a PCB to save my life LOL but they tested now days and are suppost to be using a oil that doesn't contain pcb 's . The big caps I have state on the sides of them the test date and results . I guess that depends on how much we trust the test to be accurate . I do appreachate the warning dude !! Truth is I probably glow in the dark as long as I've scrapped big electrical stuff . 

On the tumbled silver I have been getting some good results with the water seperation . I think I have most of the top layer now seperated . I had it at my house and been staying here at moms helping take care of my father . Long depressing story but he's on a vent machine . Thats one reason for the renewed interest in this stuff . I have to have something to take my mind off reality and playing with this has been a life saver for me . 

Back to the silver though when I went and got it the stuff got stirred up during the move . So i shook it up good and noticed two layers sunk fast leaving a real fine light brown stuff floating for some time . I suctioned this off and have 95% of this layer in a seperate jar 8) What ever this layer is it's now pure . Funny thing is I figured the grit would be on top but acording to the color it's not the grit . I'm now assuming the light brown / tan layer on top is my copper and my grit is the next layer . Thats just a new guess though and we know how that go's LOL 

The other two are just about identical in color but you can see a difference in the layers . I'm to a point where I have to let things settle so I can get them back into a couple jars . Kinda funny how one jar can turn into a dozen when I get to playin with them LOL .


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## Goldfinger4 (Feb 28, 2011)

Most plated cutlery is made of a Cu-Ni-Zn alloy. 12% Ni, 24% Zn and 64% Cu is the common alloy for that in Germany. 
As Harold said, the white plating under the silver is Ni.
Be careful with dissolved nickel ions, when having contact with your skin it can cause an irritation or even a nickel allergy.
I run my electrolysis until I do not see much white anymore because I think it is difficult to differentiate between corroded silver and nickel.


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## Fever (Mar 1, 2011)

I agree Goldfinger4,

It is sometimes difficult to determine whether you have corroded (or eroded, in my case) entirely through the Silver layer. But, I believe once you condition your eyes to the subtle differences, it can be done to acceptable accuracy. I have my tumbling times down to the point where I know I am abrading and removing the entire Silver plate layers. There will be small amounts of base metals in my sludges, but they should not pose a problem chemically. I have never heard of Nickel allergies- very interesting!

Fever


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## Goldfinger4 (Apr 7, 2011)

Nickel is the most frequent cause of contact allergies. That's why nickel is less and little used for steel alloys which have contact with skin.
Maybe you are immune to that 
Did you test your results for purity? I'm interested in how much % silver your dust contains.


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## Fever (Apr 9, 2011)

Haven't had the time! I have accumulated a nice amount of material, but have yet to do any chemistry. Work is crazy for me right now, but hopefully soon....


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## cbarney522 (May 5, 2013)

Hi Everyone. I've been a longtime lurker and am going to start being a more active participant on this fantastic site. I started getting into metal recovery during a period of unemployment several years ago, and it's become something of a hobby. I started with disassembling several hundred PC's that I got for free, recovering gold from edge cards, and other components. From there, I branched out into gold-plated and silver-plated metalware, and even pewter. 

I had pretty good success stripping gold from 40 lbs of gold-plated utensils last year using a sulfuric acid stripping cell. However, it was messy, dangerous and labor intensive. I have a large quantity of silver and gold-plated metalware (vases, trays, cups, bowls, pitchers) that I want to strip using some sort of abrasive method. In my opinion, this method would be safer, more cost-effective, and more scalable to large volumes.

I've read several postings from members who have used ball mills to abrade silver plating. My thinking is that a vibratory tumbler might work better and use less electrical power, but I can't find anyone who has actually run experiments on one.

My idea is to use a shop guillotine to cut up silver-plated metalware into small pieces. I will then place them into a vibratory tumbler with an abrasive media, run it with a water circulator, and slowly abrade the silver plating from the metalware. With proper design, I'm thinking that I can get a lot of the silver to accumulate in a goose neck of the water circulation system. I would run batches separately for gold-plated items.

Does anyone have any experience using a vibratory tumbler to remove silver plating?


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## rusty (May 7, 2013)

Fever said:


> Thanks for the input Rusty. I thought about sandblast, but since I already have the ball mill, and plenty of time, I thought I'd go that route. I also think the powders will be easier to collect by just dumping out my cylinder, which is tapered, into a vessel for later use. I would think the sandblast method would encourage lots of particle dispersion all about the machine, and may prove difficult to remove entirely. But, both methods should produce similar results.
> 
> I agree on the Zirconium. It's not cheap, but I believe the initial costs will be offset by the abrasive's longevity.
> 
> ...



Separating the abraded silver could be as simple as installing a cyclone. The more expensive professional sandblasting cabinets will already have a cyclone installed.

A cyclone is basically a pneumatic centrifuge.

The attached file is for making a large tumbler from old old tractor tire, I've seen where one fellow in Greendale BC actually inverted the tire having the lugs inside. He uses the tumbler for deburring parts.


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