Silver Mica Capacitors

[FrugalEE]

I was hoping that adding boxes to photos was easier than that.

That bluish purple haze on my photo of the clamped type mica is due to poor photography and overhead flourescant light. In real life the parts look a healthy silver plated color. I'm sure the surface of the mica used was clean before silvering. I don't know what might be inside the mica, but it comes out of nitric whole and it's silver plating gone. It could be reused for something like doll house antique stove window. Lead, if present, should be left behind in the spent nitric.

In preparing your first batch you may want to look for the higher values and bigger, fatter parts. If you do only values like 10 pf you are not going to get many sheets of silvered mica. As soon as I get the mess dried I'm going to count sheets from the 3000 Pf batch. There are lots more than the four I got from one 510 Pf clamp type mica.

Frugal

 

[Irons]

I was hoping that adding boxes to photos was easier than that.

That bluish purple haze on my photo of the clamped type mica is due to poor photography and overhead flourescant light. In real life the parts look a healthy silver plated color. I'm sure the surface of the mica used was clean before silvering. I don't know what might be inside the mica, but it comes out of nitric whole and it's silver plating gone. It could be reused for something like doll house antique stove window. Lead, if present, should be left behind in the spent nitric.

In preparing your first batch you may want to look for the higher values and bigger, fatter parts. If you do only values like 10 pf you are not going to get many sheets of silvered mica. As soon as I get the mess dried I'm going to count sheets from the 3000 Pf batch. There are lots more than the four I got from one 510 Pf clamp type mica.

Frugal

It's all a matter of area, just like in Gold plating.

I ordered some Russian Silver Micas for fun. 126,400 pf. Those should give a good yield. :mrgreen:

 

[FrugalEE]

Here is what I got when I filtered the digested mica capacitors. Two silver mica capacitors of 3000Pf value were hammered open, leads and end clamps removed. I did not crush the parts, but did stir during digestion. The filtered liquid was surprisingly clear instead of being green and I thought I had gotten nothing, but when I put copper in I started getting silver cement and that's still in progress.

I gave up trying to count the sheets as there are dozens. I'm wondering what that spanish peanut husk like stuff is and I'm thinking I need to stir this up good and try digesting some more to see if I got all the values.

Irons, I saw those on EBAY last night when I went to get a feel for the mica market. What a weird part, must have been custom made for some very special application. Anxious to hear how you make out on them.

Frugal

 

[Irons]

Here is what I got when I filtered the digested mica capacitors. Two silver mica capacitors of 3000Pf value were hammered open, leads and end clamps removed. I did not crush the parts, but did stir during digestion. The filtered liquid was surprisingly clear instead of being green and I thought I had gotten nothing, but when I put copper in I started getting silver cement and that's still in progress.

I gave up trying to count the sheets as there are dozens. I'm wondering what that spanish peanut husk like stuff is and I'm thinking I need to stir this up good and try digesting some more to see if I got all the values.

Irons, I saw those on EBAY last night when I went to get a feel for the mica market. What a weird part, must have been custom made for some very special application. Anxious to hear how you make out on them.

Frugal

It will be a few weeks until the weather is warm enough to work. I also ordered some of the 6800 pf orange Silver Micas for comparison. I have a feeling that the people who are selling these know what the PM content is, and are pricing the components accordingly, so, I don't expect to make anything on the experiment.

1/2% tolerance is pretty tight for that type of cap. Some precision oscillator or filter application is my guess. Perhaps it's time for a re-design of my VLF Metal Detector.

 

[dtectr]

I was hoping that adding boxes to photos was easier than that.

That bluish purple haze on my photo of the clamped type mica is due to poor photography and overhead flourescant light. In real life the parts look a healthy silver plated color. I'm sure the surface of the mica used was clean before silvering. I don't know what might be inside the mica, but it comes out of nitric whole and it's silver plating gone. It could be reused for something like doll house antique stove window. Lead, if present, should be left behind in the spent nitric.

In preparing your first batch you may want to look for the higher values and bigger, fatter parts. If you do only values like 10 pf you are not going to get many sheets of silvered mica. As soon as I get the mess dried I'm going to count sheets from the 3000 Pf batch. There are lots more than the four I got from one 510 Pf clamp type mica.

Frugal

Sorry I was unclear - I was (still) referring to lazersteve's original posts re: melting the foils directly. The BB had a purple film after the melt.

 

[FrugalEE]

Calculating yields from silvered micas:

Irons wrote: "It's all a matter of area, just like in Gold plating."
Fortunately mica capacitors usually come marked with a value that relates directly to area. What other form of E scrap has that feature? A 200 Pf cap will have twice as much area and silver as a 100 Pf cap. If we keep track of the total Pf values we are refining along with the yield in silver we can arrive at a number that will give us the ability to pretty well estimate the yield of a future batch along with acid required and an idea if doing the work is worthwhile economically.

Here is an example:

A recent closed EBAY item: 200 capacitors of 4700 Pf value for $17.

Multiply 200 by 4700 = 940,000. Since the numbers get so large move the decimal 3 places to the left leaving 940.

Multiply 940 by a yield factor of .0146 grams per 1,000 Pf = 13.7 grams of silver.

That .0146 number is strictly a guess based on EBAY price being 80% of silver spot yield. I'm hoping a number of us will keep track of their total Pf and resulting silver from batches so we can get a better number.

Plating thickness:Silvering mica is very old technology and manufacturers have long since figured out how thick the plating should be. Too thick and you waste silver and the part gets bigger, too thin and stability and reliability suffer so I think that is pretty much a constant.

Voltage rating will have a significant effect on yield per 1,000 Pf. Higher voltages mean thicker mica sheets which reduce capacitance that has to be made up by more area.

weight: This is not as good a method of predicting yield especially weight of the raw potted part. I remember seeing some dipped micas where the coating was so thin you could make out where the lead was welded to the end clamp so epoxy weight varies as will lead length with some having full leads and others having almost no lead when clipped from assemblies. If we are talking about parts where everything but the mica sandwich has been removed weight should relate pretty well to yield.

Different types of silver micas: Using total Pf as a criteria we really don't care what kind of package the part comes in when it comes to predicting silver content.

Parts rated in Mfd: The common expoxy dipped parts like shown in Steve's photo stop at 9100 Pf, but there are less common large silvered micas out there marked in Mfd. Simply take a reading like 0.01 Mfd and move the decimal 6 places to the right to get Pf. 0.01 Mfd = 10,000 Pf.

Economics: Avoid processing anything less than about 100 Pf. When you see a dozen of something like 10 Pf sold on EBAY for $5 those parts should be ending up in circuits and not processed for silver. Only the large batches of large values should be considered for silver recovery. The way to find the best deals is to total the pf count and divide by the price. The Russian parts Irons bought wasn't the highest ratio I saw, but it was close and with the Russian reputation for being generous in the use of PMs, plus the curiousity factor, I certainly would have opted for the same parts. I'm predicting that processing silver micas is going to be more for fun than profit. I'm also predicting that Irons will squeak out a bit more silver than he paid for those Russian parts.

Any comments?

FrugalEE

 

[dtectr]

8) Your ability to take "university degree talk" & translate it to "real world" is a significant asset to our "Team"
I'm sure glad you're on our side :lol:
dtectr

 

[FrugalEE]

Thank you dtectr, that means a lot to me. Let me know when I use some language that isn't clear. I never really felt myself part of the university crowd. I've always admired self taught individuals.

I'm still struggling to get a sample of Ag, but I'm gaining on it. Yesterday I had good cement and lost it again because I used too much acid. Also I found a few mica pieces in the puke that still had silver on them so I put it all back into solution and it's cooking.

Frugal

 

[Irons]

Good thinking on your rule of thumb calculations. That's pretty much how I figured it. That's why I didn't think there would be much if any profit in it. I am curious to see if there are any PGMs, since the Russians are noted for being generous in their use. As far as small lots go, it's likely to not be worth the labor but I will use any Silver recovered for Inquartation. Education is priceless.
8)

 

[blkbrdpaul]

WOW ! I just did a large clean up for a electronics manufacturer from a flood and I have boxes and bags galore of these and I.C.s along with a huge pile of electronic equip. guess I better start sorting !

 

[FrugalEE]

Some Results: I finally got a measure of cement silver recovered from a batch of two 3,000Pf silver mica epoxy capacitors. I recovered 78 mg total or 13 mg per 1,000 Pf. I was amazed at how closely that compares to my estimate (prior post) of 14.6 mg per 1,000 Pf that was based on EBAY pricing. Since I figured buying on EBAY at 80% of spot it tells me you are not likely to make any money buying EBAY parts and refining them unless you get a lot better deal than they've been going for recently.

Yield per raw weight: The two parts weighed 5.2 grams and with .078 recovered the yield is 1.5%.

The yield results on this batch are long overdue. I kept chasing my tail because I used way too much nitric. On one occassion I had the cement with only a couple of teaspoon worth of liquid and I put some heat to it and the cement all went back into solution. I finally solved my problem by sucking off water and adding new to dilute. Of course each time I did that I needed time to settle.

Acid required: Here is GSP's number for dissolving Ag: 1gram per 1.22ml of 70% nitric, but you would normally dilute your acid with an equal amount of water.

Dissolving Cu takes more than 3 times as much nitric with one gram needing 4.3 ml of 70% nitric.

Clamped mica experiment: This was from two 510Pf caps. I got some silver, but it's too contaminated with green salts, absorbed into filter paper, etc. to present a number.

Working small: When I'm processing only a couple of capacitors I need to calibrate my eye dropper (in the style of Oz) as my best graduate 10ml isn't fine enough to measure something like 0.1ml. I am getting good use out of my little scale 20 gram max with .001gram resolution.

Construction of silver micas: There are two basic ways the silver is used: The best quality parts are with the silver directly depositied and fused to the mica. The second method is with the use of a thin plastic film metallized on both sides. These film pieces are sandwiched between sheets of mica of plain mica. The plastic film is NOT electically part of the capacitor. The parts that I've taken apart so far are of this latter type. The spanish peanut hull looking material s I mentioned in previous photo must be the film material.


3160 Pf taken apart: This is a new project. The whole capacitor weighed 4.969 grams, with epoxy removed it weighed 2.949 grams. I removed the two lead and clamp assemblies and they weighed 2.058 grams. That left the mica assembly at 0.850 grams. I put that in HCl to get rid of traces of solder. After that the capacitor was easily separated into it's parts. I removed 10 pieces of 5/8 inch square mica and they weighed .461 grams. That left .389 grams or less of silver, plastic film, and some blackened metal pieces that are probably left over solder.

Conclusion: We need more data from larger batches and different people, but I think what has been posted so far should give a good idea of what is possible.