# Keyboard Mylars, what method to choose ?



## Bluebloomer (Dec 14, 2016)

As the title implies; I still have around 11 pounds of keyboard mylars to process but I'm not sure what the best method is to recover the silver, and why.

From what I have read so far there are 3 processess;

- Melting the mylars
- Recover the silver with lye and H2O2
- Dillute HNO3

As there isn't that much silver in those mylars anyway, I guess one would choose for the method with the least amount of losses. Just curious if people would share their experience with all 3 methods and perhaps bring up the discussion what method to choose and why.

If I'm correct, melting would give some loss if the heat is too high. With dillute HNO3 you would need a lot of patience to handle the mylars one by one, and with the lye one would have to be very cautious not to get burned by splashing drops of lye and hydrogen peroxide. The waste would be relatively harmles, and could be used to neutralize waste acids perhaps ?

Still doesn't bring me to choose either of 3 methods as they have all pros and cons


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## patnor1011 (Dec 14, 2016)

Now that is a good topic to follow for me too as mylars are piling up and I also do not have a clue what to do with them. The only thing I did so far I separated them to two piles, one with clean mylars and other one are mylars with small conical pieces of rubber attached where every key was. I figured that I should to separate them in case I would try to melt them I would not like to try to melt rubber.


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## rickbb (Dec 14, 2016)

I tried incineration and lost almost all the silver. It yielded a chunk of very hard black cinders that the silver was bound up in. Since I don't have a ball mill to pulverize it in and to leach out the silver of I gave up on that.

I've used the lye method with some success, and will use that in future, but I have put the mylars aside to build up enough to mess with later.

Edit(s) to add: 11lbs will yield about 1 ounce of silver using the lye method in my experience. 

Also the silver powder is bound up within the silk screen ink so very little is exposed to be able to get dilute nitric working. Separating the ink from the mylar is the first step, (and hardest), those foils of ink then can be melted with the ink burning off long before the silver melts.


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## kjavanb123 (Dec 14, 2016)

Hi,

I think dilute nitric method has many advantage over other methods I have tested.

Smelting the mylars caused some major losses of silver so I would not advise it.

I recently tested dilute and near boiling lye solution and eventhough it clear the mylars from ink and silver, in large scales separating silver and mylars are problematic.

I am currently processing 40 lbs of mylars using a 7-liter stainless steel bowl, a heater and 2 buckets to rinse the mylars.

Had I choose a larger bowl I could have put the mylar sheets as whole. For this setup I need to cut them into two pieces.

Also learned that I can put a bunch of them in hot nitric bath, by either putting them one by one or when put them as whole push the center of them dip into solution.

Here are some photos



Mylar sheets cut, before dipping them into solution,



Here is after less than a mintue into hot dilute nitric solution with some agitation,


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## Lino1406 (Dec 22, 2016)

1. 11# X 2% = 0.22#
2. Best way to remove the silver is rinsing in NaOH solution (as low as 10%). However only bigger amount will justify building of a moving cable mechanism from which the mylars would be suspended into solution


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## FrugalRefiner (Dec 22, 2016)

Lino1406 said:


> 1. 11# X 2% = 0.022#


 :? 11# x 2% would be 0.22#. Did you mean 0.2% ?

Dave


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## Lino1406 (Dec 22, 2016)

Sorry, I meant 0.22 which hardly justifies the investment


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## kjavanb123 (Dec 23, 2016)

Hi,

I processed 12 lbs of my mylars using dilute nitric acid which is heated. I cut mylars into 3 parts to fit in my 7-liter stainless steel pot.

Recovered 41 grams of cement silver, which is 80 grams less than expected silver.

So I switched to dilute lye (10% NaOH) process. This time I only removed any circuit boards from the mylars.

Used this 200-liter (50-gallon) barrel, filled 100 liter hot water, added 10 kg of lye, put the remaining mylars (12 kg) into it and heat it using a Bunsen burner I had available for almost 12 hours.

Here is a photo of setup


Mylars after 12-hour in hot lye solution, and silver removed from them by simply shaking them in a bucket of water,



Silver that fell off from mylars,



One thing that I think would make this feasible for large batch is chopping the mylars into small pieces maybe 2" or less, then process them using hot lye solution, then spin them in water using a mesh so silver is rinsed off from the mylars.


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## rickbb (Dec 28, 2016)

Remember that 10% lye will also break down the Mylar so you may have small slivers of Mylar in the ink. You only want the Mylar in the solutions just long enough to break down the bond of the ink to the Mylar. 

Also it is ink with silver in it that is being removed from the Mylars, not just silver. The ink and and slivers of Mylar will easily burn off when you get to the melt stage.


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## kjavanb123 (Apr 8, 2017)

Rick,

You are right, leaving the mylars in hot solution breaks down mylars as well.

I had a 5-lb mylars batch which I tried boil in a 7% lye solution for an hour, it detached ink and silver from 2/3 of mylars.

After separating the clear mylars from the other ones, boiled the non clean mylars in the same solution for 1 hour and it was all clean.

So based on above 2 hours of boiling would be enough to liberate silver plus ink without breaking mylars.

Also once lye process is finished, do not add water to rinse, as this puffy black floating everywhere that was not the case when only lye solution was in the barrel.

I will process the liberated silver today and report the yield.


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## kjavanb123 (Apr 11, 2017)

All,

After melting the liberated silver recovered from 3.620 kg (7.98 lbs) of keyboard mylars, I got the following due to my furnace that did not get hot enough,




After cleaning the flux with hot concentrated sulfuric acid wash abd dry the pieces it weigh 30 grams.

So based on above recovery rate for this batch my mylars was 3.75 grams if silver per lbs of mylars.

These mylars are sold in local scrap yards at $1.18 per lbs.

Here is the final shot of melted and purified silver from keyboard mylar batch



Please note this silver bar which weighs 20.46 grams is recovered from 2.120 kg (4.67 lbs) of mylars after removing the blank sheet between them also separating the carbon mylars from the original batch.


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## tortuga09 (Apr 15, 2017)

Gorgeous works,
I like this result !


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## Topher_osAUrus (Apr 15, 2017)

I tried removing the silver ink with varying concentrations of hot lye solution. Starting at 10%, then 10% with h2o2 added, then 20%, then 25% and had no luck with removing them. I did not boil the lye solution, as I was using a hdpe 5 gallon bucket, so I was at the mercy of how hot I could get the solution with my tap water (which is damn hot).

After a few hours of intermittent stirring, I conceded defeat, leaving them to sit until the next day, to see if ample time was my hold up. Alas, it was not...

2 days later, I decanted the lye solution to use for waste stream treatment and the mylars looked cleaner, if anything. All still holding firmly to their silver.

I am planning on getting a large stainless pot so I can give lye one last try. Hopefully it works, as my last options would then be dilute nitric bath, and/or melting the mylar.

Lot of work for a little silver. Thanks for sharing your results!


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## kjavanb123 (Apr 15, 2017)

A regular iron barrel works fine, I added 1 kg of lye to 13 liter of water, and heat it and put the top on, after 2 hours everything was liberated.

If you put it longer it will attack the mylars and make them soft separating silver becomes pain.

Hope it helps


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## Topher_osAUrus (Apr 15, 2017)

kjavanb123 said:


> A regular iron barrel works fine, I added 1 kg of lye to 13 liter of water, and heat it and put the top on, after 2 hours everything was liberated.
> 
> If you put it longer it will attack the mylars and make them soft separating silver becomes pain.
> 
> Hope it helps



Thanks again!

You had no need to add peroxide?

Also, in an earlier post in this thread, you mentioned separating the ink foils and mylars is problematic. Was that before the spinning mesh idea/method? (I see a huge salad spinner in my mind :shock: )
Was this effective enough to remove the majority of the silver ink from the barren mylars?

Also, did you encounter any issues with the silver under the black carbon trace coverings, and the green material (no idea what to call it, I can post a picture, if required) that also covers some traces?

I have 11lbs I need to get done, a month ago, with the potential for 100lbs more, I have been racking my brain to find an economically feasible method, but so far, it seems as if mylars are a very difficult product to process profitably. 

Although, should a large scale process be deemed worthy, and start up cost minimal, there could be an almost endless supply of the mylars from members who have been waiting for a brainstorm breakthrough to come about.


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## kjavanb123 (Apr 15, 2017)

Topher_osAUrus said:


> kjavanb123 said:
> 
> 
> > A regular iron barrel works fine, I added 1 kg of lye to 13 liter of water, and heat it and put the top on, after 2 hours everything was liberated.
> ...



I did not add any peroxide, just mylars, water then lye and let it get near boil.

First batches I did not remove the black sheet between the mylars nor removed the carbon mylars.

But in first batch I left the mix on heat for almost 10 hours so that made a mess and dissolved mylars as well, so ended up incinerating and melting with flux to get the silver.

What I realized when cleaning the mylars is that after silver is detached, just a quick spin in lye solution would remove any traces stuck on mylars, so for large batches here what I have in mind,

An steel or iron tank squared shape, fill 1/3 with lye solution, heat source under the tank, a meshed pipe, maybe 1/2" in size, that is attached to a gearbox to spin the mesh barrel which hold the mylars, dip into solution and let it spin for 2 hours.

I would assume spinning it make the silver to fall through the 1/2" holes onto the tank.

I will try it in small scale and report my finding.

I really like the mylars, so easy and silver adds up quick.


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## Topher_osAUrus (Apr 15, 2017)

kjavanb123 said:


> I really like the mylars, so easy and silver adds up quick.



:shock: 
You're crazy! :lol: 

That idea is exponentially better than what I had in mind. By far.

I was thinking of just having a large stainless pot containing strips of the mylars inside of a type of collander, or bucket with slots, so I could just pull it up and hope that the ink migrated away from the mylars and through the holes or slits in the collander bucket after agitating it. Similar to how some do their close cut fingers and such.

The problem i forsee with that though, is the mylars have the tendency to adhere to one another when they are wet. Some like to only stay partially submerged. Also, I'm not sure if the integrity of the collander bucket would decline after prolonged boiling in lye.

There are a couple other ideas I have on making a larger scale with partial automation, but, since the lye needs to be dangerously boiled. Those ideas now seem half baked, at best.

I eagerly await your results :!: Thanks again!


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## butcher (Apr 25, 2017)

How about running the sheets through a paper shredder to make long slivers which can twist like spaghetti.


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## kjavanb123 (Apr 26, 2017)

Butcher

That is what I thought while back, but wouldnt that increase the volume of mylars? I have not tried it but unlike x-ray films which can twist easily, mylars tend to be softer.


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## upcyclist (Apr 26, 2017)

butcher said:


> How about running the sheets through a paper shredder to make long slivers which can twist like spaghetti.


Good idea! More and more shredders these days are cross-cut shredders for security & bulk reasons, so be sure you know what kind of shredder you've got (or are considering buying). Otherwise you'll just end up with taconni instead of spaghetti


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## kjavanb123 (Apr 26, 2017)

The following links two homemade shredder and cutter that can be used for mylars or films.

https://m.youtube.com/watch?list=PLxXd0CgIkAPId55oGBeq2Dm1_IQfj5pWK&v=HT_7hMs3WBI

And
https://m.youtube.com/watch?list=PLxXd0CgIkAPId55oGBeq2Dm1_IQfj5pWK&v=4S2tKhAru2k


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## dscrapper (Sep 12, 2017)

I process about 6 lbs of keyboard mylars with the Lye . 10% lye . all came clean then I incinerated . I smelt with borax and sodium carbonate as a flux to catch the ash. My problem is the silver looks as thou its got gold in it. Anyone ever heard of some keyboard from PCs mylars having both silver and gold ?


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## Topher_osAUrus (Sep 12, 2017)

Id bet its firescale from a bit of copper contamination (somehow) over it being gold. Try putting a couple pieces in a small beaker with a little distilled water and then add some nitric. If its firescale the oxidation will quickly be removed and leave shiny silver.

Sulfuric can work too, just not as fast. It has the benefit though, of not dissolving a small bit of the silver with the oxidation.

Pictures would be cool.
I love me some pictures


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## butcher (Sep 12, 2017)

I like the home made paper shredders, guards are also easy to make,that way even I could keep my fingers from being mistakenly shredded. for some reason my fingers are always attracted to fast moving objects.


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## dscrapper (Sep 13, 2017)

Topher_osAUrus said:


> Id bet its firescale from a bit of copper contamination (somehow) over it being gold. Try putting a couple pieces in a small beaker with a little distilled water and then add some nitric. If its firescale the oxidation will quickly be removed and leave shiny silver.
> 
> Sulfuric can work too, just not as fast. It has the benefit though, of not dissolving a small bit of the silver with the oxidation.
> 
> ...




I think you may be right about the copper . I cant get and nitric to try . I do have more of this powder to smelt but am waiting until I figure out what to do with it . since it is copper can I use hcl in my powder and remove it ?


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## Topher_osAUrus (Sep 13, 2017)

dscrapper said:


> I think you may be right about the copper . I cant get and nitric to try . I do have more of this powder to smelt but am waiting until I figure out what to do with it . since it is copper can I use hcl in my powder and remove it ?




I wouldnt use HCl.
But I hate silver chloride.

I dont know how much AgCl would be created even, probably minuscule amounts, but thats still too much for my liking.

Can try to pickle it in battery acid, or after its melted quench it in dilute HCl


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## lg701 (Sep 21, 2017)

I use normal household bleach from Walmart (8.25% sodium hypochlorite). Biggest problem is it 
takes quite awhile to get the silver off the mylars. Evidently the ink is the determining factor in how 
long it takes. Some mylars take days, others take weeks. Agitation from time to time is required as it is with a lot of the processes we do.
Much safer process but patience is a virtue.


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## kjavanb123 (Sep 21, 2017)

lg701 said:


> I use normal household bleach from Walmart (8.25% sodium hypochlorite). Biggest problem is it
> takes quite awhile to get the silver off the mylars. Evidently the ink is the determining factor in how
> long it takes. Some mylars take days, others take weeks. Agitation from time to time is required as it is with a lot of the processes we do.
> Much safer process but patience is a virtue.



You may also heat your lye solution that will shorten the time needed for mylars to get clean.


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## rickbb (Sep 21, 2017)

When using bleach with x-ray film the process of stripping the silver bearing emulsion converts the bleach to lye eventually leaving only lye in solution and no bleach. 

Could be something similar going on with the Mylar's, the bleach converting to lye before the stripping occurs, which is why it takes a long time.


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## lg701 (Sep 22, 2017)

Are we talking about the same thing here? I'm using sodium hypochlorite, not sodium hydroxide. 
My apologies if I'm wrong, but I'm not sure normal bleach turns to lye under any circumstances.


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## rickbb (Sep 22, 2017)

lg701 said:


> Are we talking about the same thing here? I'm using sodium hypochlorite, not sodium hydroxide.
> My apologies if I'm wrong, but I'm not sure normal bleach turns to lye under any circumstances.



Yes, bleach, sodium hypochlorite, will be converted to sodium hydroxide in the process of dissolving the emulsion of x-ray film to release the silver salts. Several patents and papers published by Kodak back in the day talk about this.

I don't know if anything similar is happening on the resin, (silk screen ink), that is binding up the silver on keyboard Mylar though. Since you mentioned it took a very long time for the bleach to breakdown the bond of ink to Mylar. And since we know that lye works for breaking that bond, I thought about the conversion process that happens with x-ray film and bleach. 

Was just thinking out loud on it, and could be completely wrong, (wouldn't be the first or last time I'm sure).


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## lg701 (Sep 24, 2017)

Thanks for the heads up about using bleach with x-ray film Rick. If I had access to any amount of
x-ray film I would have tried that next. I think I will pass on that adventure.
Besides the agitation I sieve the liquid and add fresh every 5-7 days. I figured if it evaporates
from our gold solutions before dropping, the same must happen here.
Even though we all use bleach for laundry and find it in lots of other cleaning products it goes 
without saying that it should be kept out of reach of children and pets.


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## kjavanb123 (Mar 27, 2021)

Hi everyone

I happened to receive 822g (1.81 lbs) of mylars (with that blank sheet between them). There were 41 pieces.

I used 10% lye solution (that is 10g lye mixed with 100ml of water).

Here are some pictures, 



Here is what mylar looks like after 1.5 hrs of boiling in lye solution. 



This time instead of filtering the ink and silver and melting them, I washed them into a beaker and dissolved the silver in nitric then filtered and added hcl to drop the silver as silver chloride.



Here is the silver chloride. After being washed few times I sprinkled zinc powder and mixed it with silver chloride, then added hcl to convert to elemental silver.



And here is the final silver shots from that mylar batch. 



So net weight of silver from this batch is 9.05g silver from 822g mylars (41 pieces).

This calculates to 11g of silver per kg of mylars. Or 6.1g silver per lbs of mylars. In my last batch I did direct melting the silver and ink I got 6.7g silver per kg. 

So it seems filtering the liberated ink and silver, then dissolve it in nitric filter and drop with hcl or cement with copper would be a better option. 

Locally I can get mylars for about the price of 4g of silver per kg, so if I can get 11g silver from a kg of them, seems like a good deal. 

Also I used a centrifuge to separate the silver inks from the mylars. 

Best regards
KJ


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## rickbb (Apr 1, 2021)

In my opinion you went to a lot of extra work and chemical expense reducing your profit. 

The silver in the ink/resin is almost pure as is. The last batch of Mylar's I did after I had separated the ink from the Mylar, after washing and drying, I simply melted it with some soda ash as a flux. 

The melt process will carbonize the ink/resin and any bits of Mylar and that will either go up in smoke or get trapped in the soda glass which you can break off of the silver bar/button when cool. 

My yield was approximately 1ozt per 10lbs of Mylar's.


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## kjavanb123 (Apr 1, 2021)

rickbb said:


> In my opinion you went to a lot of extra work and chemical expense reducing your profit.
> 
> The silver in the ink/resin is almost pure as is. The last batch of Mylar's I did after I had separated the ink from the Mylar, after washing and drying, I simply melted it with some soda ash as a flux.
> 
> ...



Hi Nick

The reason I did the extra step was to avoid the smoke from ink plastics in melting and dealing with lower volume of metals. 

Based on my finding from 10lbs of mylars you should have gotten almost at least 2 ozt. Hence another reason for my extra step.


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## kjavanb123 (May 13, 2021)

Hi

Just finished processing 6kg (~12lbs) of mylars in 10% lye solution, boiled for 1.5 hrs.

Recovered 58.51g silver. This makes it close to my last yield of 10g per kg of mylars. 








Best regards
KJ


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