# Acid Peroxide on Teflon Fiberglass



## FrugalEE (Sep 10, 2010)

I'm new to the forum and this is my first refining project. The material I have to process is primarily 12 X 17 inch teflon fiberglass .0062 in. thick. It has etched runs (some .023 In. wide and some .050 In. wide plus some 3/8 In. pads) covering about 10% of the board on both sides. It was manufactured back in about 1982 and I have good reason to think that the applicable specifications are 1/2 ounce copper (.0007 In.) plated with nickel at .000100 In. minimim with gold on top of .000050 In. minimum. I have painstakingly measured the area and calculated the amount of gold (assuming 50 microns) and it comes out at .76 grams per board and that definitely looks worthwhile to me.

In searching the forum I have not found any other reference to recovering gold from teflon fiberglass PWD. Last night I started an AP process about 9 PM in a new white dishpan with a third of a board using Steve's recommended 2 parts HCL to 1 part peroxide. It is going to be very slow, but thats OK, especially if I get most of my gold in the form of foils. We are now over 12 hours into the process and most of the runs are off, but we're still working on some 3/8 In. diameter pads and the solution is still not very green. The foils seem to be black on the bottom when they first come off, but seem to get better with time. Is that the nickel?

Steve's AP videos were great for teaching me techniques, but there are some very significant differences with what I have to work with:
1. I have very little copper mass compared to his 600 grams of card edges
2. My Cu is .0007 thick and his was probably .0014 In.
3. G10 board is much more of a sponge than teflon board so etchant can more easily get to the Cu.
4. Teflon is hard to wet
5. Teflon sheets are going to stick together much worse than fingers and I have to process sheets much like developing a photo print - one at a tiime. I don't have plastic tongs yet so I'm poking and scraping the runs with a plastic rod.
6. My material has been in a PVC bag since 1982 & part of time in a hot garden shed. It probably has a film on it similar to windshield fog in new car.
7. Temperature: I believe Steve got a pretty good reaction that fed on itself and heated up his solution. Also he is in a much warmer climate. I as processing at about 70 degrees. 
8. I don't have any solder or solder mast to deal with only clean unused PWB.

Interventions: I added a few drops of Kodak Photoflo to reduce surface tension. It foamed a bit and I think it helped. I also used a tiny patch of bare Cu PWB to check etch power a couple of times. My next piece I plan to clean first with Pro windshield spray that I got with a new windshield.

Questions: Because of the slowness I'm concerned that a shelf life sort of thing will cause peroxide to die before it has a chance to create the CuCL2 etchant. Is that likely? I believe Steve was adding peroxide refreshers primarily because he used it up etching Cu. 

Should I raise the temp? My inclination is to do this by putting etchant dishpan in a larger pan with hot water. 

My immediate objective is sort of an assay ie to process enough so that my $12 HF digital scale will confirm the gold content. I may send off the rest for processing.

Suggestions please and thanks for all the great info on this site. I've been burning up my eyeballs trying to soak it all in.

FrugalEE


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## gold4mike (Sep 10, 2010)

If you have some foils floating free you have begun to dissolve copper. As many people have stated on the forum "Patience is a virtue", especially when working with A/P. As more copper gets into solution the reaction will start to work a bit faster. I have never seen it generate any noticeable increase in temperature. 70 degrees should be fine, but if you want to add heat, don't overdo it. 

I have used the same gallon or so of A/P for about 15 pounds of edge fingers and it continues to work very well. I have added to the solution when I rinse my foils by dumping my rinse acid or rinse water through the filter right into my A/P bucket. The additions allow for more dissolution and I already have the dissolution power built up from much copper in solution. It's now probably closer to two gallons in volume so I store some of the extra in another bucket, ready to start over when my main bucket finally gets saturated with copper. 

As for additions of H2O2 - I use an air bubbler like you would use in a fish aquarium and haven't had to add any H2O2 since my original mixture was created. I don't have to worry about putting any gold into solution and having it drop as fine powder that might go through my filter.

If your pieces are large you might benefit from cutting them into smaller pieces so you can fit more in your container. The extra access on the edge of the cut might help the solution get at the copper a bit quicker.

It sounds like you're on the right track, just don't try to rush it. The longer it takes the more value your gold button will probably have!


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## FrugalEE (Sep 10, 2010)

Mike,

Thanks for quick reply. What I started with was only a third of a board as my dish pan was too small otherwise. I added another piece and was surprised to find that sheets sticking together wasn't the problem I expected. Maybe chopping into small pieces would be a good idea and deliberately cutting acrosss the max number of runs. I wonder if this material in a completely stripped form would be useful to anyone. 

I bought a bubbler yesterday, but haven't used it yet as the solution is still pretty light. Perhaps I should have jump started the solution by adding pure Cu before adding my gold plated boards which obviously have the Cu pretty well covered. My concern was the peroxide would die before enough Cu got attacked. A second board I put in 90 minutes ago still is holding tight to it's runs. This board holds runs far better than G10. I tried hair drier and knife to get a run sample and didn't have much luck. Torching teflon doesn't sound like a good idea as I've heard it puts out a very poisonus gas at high temperature. I'm willing to let the process take days especially if it avoids putting Au into solution and lets me judge Au content by foil weight.

When you terminate the batch are your foils shiny gold on both sides? Mine look black. I also get black on the board after part of the little round pad has come off. I suspect that is some kind of carbon used to get conductivity to electro deposit the copper.

FrugalEE


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## gold4mike (Sep 10, 2010)

The black is probably a little bit of gold that dissolved initially and cemented back out as copper started going in. That's part of the reason I keep using the same A/P over and over again. Eventually I'll run my spent liquid through a much tighter filter to try to catch all that I can. Since another fresh batch of fingers is going in the bucket anyway, I filter through one coffee filter for speed and if a few foils run over the edge I'll catch them next batch. I just finished a run of 2 pounds of fingers, every other day, until I hit 10 pounds. I got a 21.5 gram button already, have two beakers still settling the last bit of powder, and have the original fingers to sort through and reprocess those that still have some gold stuck to them. I had a three day weekend and was determined to melt my first button.

I'll be interested to see what you get from your material. From your description it is something I have not yet seen.

You are correct about the Teflon and toxicity. I used to haul piping to a place in TN from the Dupont plant in Washington, WV. When a process would screw up the material would stop moving and solidify in the piping. They would disassemble it, load it on my truck, and I would take it to TN to have it burnt out of the piping. This was (I was told) the only place in the Eastern half of the US that had the permits to burn this material out. It was a 12 hour burnout, then a cool down, load my truck and off I would go back to WV.

There is currently a big to-do about C-8 from their manufacturing process getting into the drinking water of several surrounding communities.

I wouldn't recommend trying to burn it at home!

Good luck and keep us posted on your progress.


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## goldsilverpro (Sep 10, 2010)

How many sheets of this material do you have? It there are many sheets, I would try to find a way around doing only one sheet at a time.

Sheets of x-ray film also stick together when wet and this greatly slows the stripping solution from getting in between the sheets. Some people first run the sheets through a paper shredder. This distorts the shredded pieces of film and totally prevents the pieces from mating together and sticking. The only problem is that this great distortion produces a product of low bulk density - maybe 1/5 of that of the same film cut into small flat pieces.

Were it me, I would try one sheet (or, 1/4 of a sheet) of your material in a paper shredder and see what happens. It's very thin and should shred easily. I would first get the shredder immaculately clean in case some of the gold/copper flakes off - or buy a new shredder. Also, I would think that this would expose more copper and make the acid work faster.

After the copper is gone and the material is rinsed, the gold could easily be leached from the teflon with AR or HCl/bleach.

Just an idea, but I think it's worth a shot

Chris


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## FrugalEE (Sep 11, 2010)

Mike,
Thanks again for some more good ideas and I'm impressed with how much you have run through that solution. You haven't said if you bubble while etching or just after a batch. I've been running my small fish air pump since about noon and I'm sure it helps agitate the mix. Some of the runs I just brushed off from boards I added about noon today have a silver color (nickel?) underneath. My first board put in over 24 hours ago still has not etched off all of the 3/8 inch pads.

Interesting story on your tie with teflon.

Chris,
Shreading sounds like a pretty good idea. Thanks! I don't have one, but this batch is certainly big enough to justify buying one. I have about 100 of the 12 X 17 boards and about 25 boards 12 X 12. 

From what I've read this sounds like a job for your cement mixer cyanide process.

FrugalEE


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## Oz (Sep 11, 2010)

I have not seen Teflon boards let alone boards without masking, where did these come from? 

Since you do not have a lot of this material (as to # of boards) I would run them in dilute nitric. Get a plastic dishpan #2 plastic (high density polyethylene) and stack the boards on top of each other with glass or stainless steel pieces between them to keep a gap. This is not cost effective for most boards but if your gold content math is correct it makes sense in this case. 

If you do not have access to nitric I would run a sample for you free of charge to determine the gold content for you, mainly because I am curious to see a Teflon board.


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## goldsilverpro (Sep 11, 2010)

> Chris,
> Shreading sounds like a pretty good idea. Thanks! I don't have one, but this batch is certainly big enough to justify buying one. I have about 100 of the 12 X 17 boards and about 25 boards 12 X 12.
> 
> From what I've read this sounds like a job for your cement mixer cyanide process.
> ...


In this case, due mainly to the configuration of the material, I don't think that the cement mixer cyanide process (using NaCN and H2O2) would be the way to go. This system relies on 2 things - that a nickel barrier exists between the gold and copper and that the stripping be done very quickly (maybe, within 1 to 4 minutes. If it is not done quickly, the nickel will slowly degrade in the cyanide or it will abrade by the tumbling action. Once any nickel is gone and copper is exposed, the gold that is dissolved will tend to immerse (cement) back onto the copper. Another problem with long cycle times is that the H2O2 destroys the cyanide quickly. If you tried to run multiple sheets in the tumbler, they would stick together and this would increase the time considerably. If you shredded the material, this would expose copper and would create big problems.

If I were to use cyanide (which I probably wouldn't), I would use m-NBSS (ludigol) as an oxidant, rather than H2O2. It's a little slower, but it doesn't destroy the cyanide as badly, if at all. I would put it in a tank or bucket and heat it to about 120F. However, unless you made a plastic rack (or, something) to keep the sheets separate, you would have to run the sheets one at a time.

I'm still thinking about what is the best way to process this material. I wrote you up a long procedure for shredding and then using nitric but then I saw potential problems and deleted it. The problem was that the gold foils would be trapped in a very large volume of shredded teflon. This would take a lot of acid (AR or HCl/Bleach) to dissolve the gold or it would take a lot of batches.

Two possible reasons you are having trouble dissolving the copper are that (1) There is a film of something on top of the gold or (2) The gold is non-porous and the acid can't penetrate through it to get after the copper. If (1) is the answer, you'll have to clean it off somehow. I noticed that you've already thought of this but you'll have to careful with what you use. Some windshield wiper fluids contain silicone and that would not be good. If (2) is the problem, it will take forever in the HCl/H2O2. I lean towards (2) but I could be wrong.

This may be heresy, but I'm wondering if dissolving all the metals, Cu, Ni, and Au, in HCl/bleach (or, AR) might be the best way to go. This would solve (2) above, if that is the only problem. Also, it would make it a one-step deal. This could be done by shredding or leaving the sheets whole (or cutting them into smaller pieces). If shredded, it could be placed in a bucket with holes in it and this would be placed in a larger bucket containing the solution and the inner bucket could be bobbed up and down occasionally. If sheets are run, you'll need to figure out some way to run multiple sheets by keeping them separated - Oz had an idea about how to do this. The clean teflon doesn't wet and could then be simply rinsed of solution and it would be out of the picture. According to your data, there is a total of about 8 oz of Cu and 1.2 oz of Au on the sheets - not a terrible ratio. The gold precipitated would probably not be clean but it would be simple to re-refine it. You'll probably need to evaporate the solution down (say, to 1 gallon) to make the precipitation more efficient. Or, maybe you could add a little nitric and then cement out the gold on copper buss bar.

Please note that these are just ideas. I'm here and the material is there. If I had a lab (which I don't) and started experimenting with this (in very small amounts), I might find problems, change my mind, and go in a totally different direction.


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## dtectr (Sep 11, 2010)

do you have any of this laying around?


check out the CuCl pdf from Lazersteve's profile page. Since this is basically hwat you're doing by copper etching, 
adding Copper Oxides can speed saturation of your solution, i believe.

but i could be wrong.


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## FrugalEE (Sep 11, 2010)

Three good replies. Thanks guys!

Oz,

This is RF circuitry and the boards I am working with are the conducting part of a stripline sandwich. 30 mil teflon fiberglass panels are laminated to either side and then metal plates containing the connectors on one side and held together with bolts or rivets complete the assembly. There was no soldering involved in the assemblies I worked with and mechanical connections were used. The boards I have were rejects that never got sandwiched. If you find working assemblies in the field you are going to have to use something like a 400 degree oven and a pair of pliers to rip apart the sandwich. Most RF microwave circuitry now is done with microstrip where there is only one ground plane and the circuitry is readily accessible.

I have a small quantitiy of dilute and very pure nitric, but I should be able to buy nitric locally. I'm going to have to do the math on this and study it more, but it seems like a pretty good idea. I presume it would attack the gold less than A/P and might also have advantages in recovering the Cu and Ni. I'm a bit surprised you mentioned using stainless spacers. I doubt all types of stainless would be suitable and there is so much plastic available I would probably stick with that, but I believe I read somewhere on this forum that nylon is susceptible to some acids.

GSP,
There is probably no way this teflon material is going to tumble without trapping some pieces requiring some human intervention and I see how that rules out your tumbling cyanide process. As I see it the quantities here are too small to think about a slow cyanide process as the usage of acids to etch all of the metals involved are not that high.

dtectr,
Yah, I got some oxidized copper. I've treated copper almost like gold for most of my life. I'll study the CuCL2 etch process some more.

My etch bath has some runs coming off that are several inches long. I expect to terminate this batch sometime this week end and cut out any areas that still show metal and put them in another batch.

I'll see if I can do some pictures. I'm quite familiar with editing & sizing photos, but I've never posted one.

FrugalEE


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## FrugalEE (Sep 11, 2010)

GSP,
I went back to reread everything before going to a study phase and I found a lot more great material in your post that I either overlooked or you somehow added at a later date. I have little experience using forums. I finally printed out all this thread so I can refer while writing.

I'll comment a bit:

Windshield spray: I avoid silicon as I know it messes up finishing. I failed to read the label before using, but in this case I appeared to luck out as there is no mention of silicon. The spray is from Safelite Auto Glass and contains in descending order: Water, Butoxyethanol, Ethyl alchohol, Methanol, n-Butane, and Propane. I couldn't see that it did anything. I said the boards were is PVC bags, but I expect it's polyethylene. 

The process seems to be working better now that it's aged a bit and I'm using a bubbler. The first board, which is approaching 48 hours now, is almost bare even at the 3/8 In. round pad. The second board I put in has some strange blackish deposits that won't etch off, but the pieces put in afterward seem to be running better. I'm getting more foils now that are gold shiney on both sides. If I were to start this over I would get my bath working better with some oxidized copper before putting any of my teflon boards into it and I would use the bubbler from day one and maybe no H2O2 at all. If I have a good settup and can process at least 6 boards at a time it's acceptible to me to have it take 2 days per batch if I can process something like 5 boards at a time with only occassional tending.

I've been pulling off some spoonfuls of runs and putting them in a separate dish with some of the A/P. That makes it easier to evaluate the boards I'm still trying to finish up.

I think the thicknesses are: 50 microns of gold over 100 of Nickel over 700 of copper. The copper should be pretty close, the others are minimum. The worst case ratios should be 14:1 copper/gold or 16:1 base/gold. You somehow got 8:1. Are you basing that on average thickness in use in early 80's? By the way I used your eraser test and dozens of strokes didn't seem to phase it. From what I remember of reading the spec the gold has to be 98% pure or something like that. I'm wondering what the impurities might be?

It's probably not economical, but I would like to have a pile of nickel and a pile of copper, at least in powder form out of this at the end and no significant hazardous waste. Which process A/P, dilute HNO3, or A/R is easier to remove base metals from?

My only previous experience with HNO3 was back as a freshman in college where we dissolved a dime to measure the silver content. That tells you I'm over 65.

I really appreciate your time.

FrugalEE


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## Oz (Sep 11, 2010)

I personally would use nitric on these boards as if your yield estimates are correct it becomes cost effective. The nitric will not affect the gold and will digest the other metals you have. Any solution containing hydrochloric can put gold into solution.

As to my stainless comment... 
I have 300 series stainless that has been in nitric for over a year with no problem. There are stainless alloys that you may have troubles with but I have never had a problem if I use food grade stainless. I actually use glass rod as spacers for this type of material, but it is not worth buying just for 1 use. Most craft stores would have glass buttons or such in a convenient shape for a couple of dollars. They would also likely have stainless tweezers or forceps that are nice for playing in nitric with.


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## goldsilverpro (Sep 11, 2010)

> I think the thicknesses are: 50 microns of gold over 100 of Nickel over 700 of copper. The copper should be pretty close, the others are minimum. The worst case ratios should be 14:1 copper/gold or 16:1 base/gold. You somehow got 8:1.


You're talking thickness and I'm talking weight. Gold is about twice as dense as copper. If you want me to go through the math, I will.


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## FrugalEE (Sep 12, 2010)

Chris,

You are right and I realized it a couple of hours later. I hoped to correct my error before you posted. I've been working through some math & studying chemistry while baby sitting grandkids. My ratios are on volume, but mass is what is important and the mass ratio of Cu to AU is about 6.5 to 1. It could be even lower if Gold exceed the 50 micron minimum by very much. Gold being so dense really helps things. 

I did some further calculations on amount of Nitric needed. Your rule of a "liter of 50/50 Nitric and water will dissolve 120 grams of Cu" says that about 4 liters of solution or something like half a gallon of concentrated HNO3 would be enough to do 100 of my boards. The question is whether nitric will penetrate the gold layer on my boards and speed up the process any better than A/P method. Oz states it will at least be more selective in that it won't attack the gold. The cost of chemicals doesn't seem to be much of a factor, it's more the labor and minimizing the mess. I'll run some tests on a small scale with HNO3. I have about a liter of 2%. I could concentrate that some or try as is.



OZ, Approximately what strength HNO3 do you recommend? I would like to send you some kind of sample of my board for you to experiment on, but I don't know how to get a private communication going. I'll try to figure out the forum proceedure for doing that tomorrow. 

I have nice stainless tongs left from photo work years ago. I"m not puttin them in A/P, but you've given me reason to believe they would be OK in HNO3.

FrugalEE


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## Harold_V (Sep 12, 2010)

FrugalEE said:


> I have nice stainless tongs left from photo work years ago. I"m not puttin them in A/P, but you've given me reason to believe they would be OK in HNO3.
> 
> FrugalEE


Should you make an inquiry for a large volume of nitric, you'll come to understand it is packaged in stainless. 300 series stainless, as Oz has explained, does not react with nitric, and is the metal of choice for such use. I have an 8 gallon container (military surplus) that is likely nearly as old as I am, and has contained nitric acid for the past 25 years it has been in my possession. I kept a small amount of nitric when I sold my refining business, knowing it would be useful for passivation of stainless (I am a retired machinist/toolmaker). 

Harold


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## Oz (Sep 12, 2010)

2% nitric is very weak but given time it would still do the job. I would add heat to help but I really have no idea as to how long that would take as I have never worked with it that dilute. At 2% and high purity I would guess it is intended for photography and it would be expensive to waste it on these boards. 

I use 70% ACS grade nitric and have never found the need to add more than an equal volume to water. I would do my best to estimate the nitric needed to digest the base metals then start with a container (that you can place your boards in) that has an equivalent quantity of distilled water as the nitric you expect to consume. Put some of your boards in the water and measure your nitric into a seperate container. Start by adding small amounts of nitric giving it 15-30 minutes between additions until you reach an acceptable dissolution rate. Adding too much nitric at once causes you to waste it as a fast reaction will cause much of it to gas off as red NOX fumes. To economize on fluid volumes I would run multiple batches of boards in the same solution adding nitric as it is needed.

I doubt you will want more than a 25% by volume of 70% nitric at any given time replacing it only as it is consumed. Be patient in adding nitric as the reaction to copper is exothermic and as it heats up the reaction rate speeds up and you can find yourself with a runaway reaction foaming acid and gold foils out of your container.

I have replied to your PM.


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## goldsilverpro (Sep 12, 2010)

Sorry, but it seems my math was terrible in my previous posts. I went by your figure of .76 g of gold per board and that isn't right. There are 12 x 17 x 0.1 = 20.4 sq.in. of plated area per board. At gold .00005" thick, the total gold per board would be .00005 x 16.38 x 19.3 x 20.4 = .322 g. You have an equivalent of 117, 12x17 boards. Therefore, the total gold would be .322 x 117 = 37.7 g, or 1.21 tr.oz.

For the total copper, it would be .0007 x 16.38 x 8.9 x 20.4 x 117 = 243.6 g. The Cu/Au ratio is 243.6/37.7 = 6.46/1

Don't forget the nickel. The nickel is .0001 x 16.38 x 8.9 x 20.4 x 117 = 34.8 g.

The total Cu + Ni = 243.6 + 34.8 = 278.4 g.

A gallon of 70% nitric will dissolve about 2# of Cu + Ni, or 908 g. To dissolve 278.4 grams, it would take about (278.4/908) x 3.785 = 1.16 liters or 2.32 liters of 50/50 nitric.

To explain the math. In the 1st paragraph, one sq.in. of .00005" thick gold has a volume of .00005" x 1" x 1" = .00005 cu.in. The 16.38 figure converts this to cu.cm. (cc). The 19.3 figure is the density of gold in g/cc. The same logic was followed in calculating the Ni and Cu. Ni and Cu both have a density of 8.9 g/cc and it takes about the same amount of nitric to dissolve either Ni or Cu.

In case you wanted to dissolve everything (Au, Cu, Ni = 316.1 g) in AR, the calculations are about the same as nitric. It would take about 1.32 liter of 4:1 aqua regia. The AR could be diluted somewhat to increase the volume but, the more it is diluted, the slower it will be. It would probably work faster if the dilution were made with extra HCl, rather than with water.

I think all the math is right this time but, if anyone spots a flaw, please let me know.

Experiment! Experiment!


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## Oz (Sep 12, 2010)

Great post showing the math behind calculating these things when plating thicknesses are known. I have not checked all the math as I have not finished my first cup of coffee yet, but I think you may have missed the boards had traces on both sides equaling 10% of the surface area.


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## FrugalEE (Sep 12, 2010)

Oz, Thanks for the general proceedure on HNO3. When you first mentioned dilute HNO3 I thought you might have meant a much weaker solution. I found my HNO3 stock and it is only about 35 ml of 2% so I"m going to have to use that very carefully in my one and only test tube to try and gauge speed of response to samples of my PWB.

Harold, Nice to have you join us. That fact about stainless containing concentrated nitric for years is one of those mind warping things. Some day I'm going to have to find out how that works. I could use a hint on figuring out if a stainless implement is OK or not. My photo tongs I bought back in the 60's are marked CESCO and are non-magnetic. I suppose one could test with a drop of acid and look for reaction, but I wouldn't chance use in anything where purity or accuracy was critical. Can one easily determine if something unmarked is 300 series?

GSP, I calculated much like you, but there are pretty similar runs on BOTH sides of the PWB. (That's to provide controlled coupling to form quadrature hybrids.) Also 10% was an approximation and I actually got 24 sq.In. on the side I evaluated. While digesting your math I realized my first post is in error on the size. The large board is actually 12 X 21 inches instead of 12 X 17. Sorry about that.

I can use your acid estimates just by doubling to cover both sides. I see an interesting dilemma in using A/R in that to run multiple boards convienently you need a lot of solution that isn't going to be used up. If we have to go that way I hope that the time per board is at least fairly short. I expect it will be, but have no experience at all. It appears to me that short of keeping temp down there is no way to slow down the fuming like there is in the proceedure using only Nitric that Oz wrote.

FrugalEE


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## Oz (Sep 12, 2010)

FrugalEE said:


> I see an interesting dilemma in using A/R in that to run multiple boards convienently you need a lot of solution that isn't going to be used up. If we have to go that way I hope that the time per board is at least fairly short. I expect it will be, but have no experience at all. It appears to me that short of keeping temp down there is no way to slow down the fuming like there is in the proceedure using only Nitric that Oz wrote



When using AR you can start with concentrated HCl and only add your nitric incrementally as needed. It is actually the preferred way to use it as any excess nitric will need to be removed before precipitating your gold.


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## joem (Sep 12, 2010)

could you not just use an electric drill or dremel with a wire brush wheel to get the layer of gold off, and a vacuum to collect. This would minimize the amount of metal to deal with when processing.
my thought


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## goldsilverpro (Sep 12, 2010)

I am really enjoying this thread. It gets down to the nitty gritty of what refining is all about - setting up goals, experimenting, and then going with the best bet. I would think the goals should be such things as simplicity, speed, inexpensive set-up, small amount of waste, low chemical cost, and, most important, efficiency - you want to get essentially 100% of the gold. Also, there are questions such as what amount of fumes your setup will tolerate.

Sorry, I didn't notice that both sides had traces. Back to square one.

From your most recent figures, there are 5472 sq.in. of plated area on the 2-sided 125 sheets ([email protected] and [email protected] - your figure of 24 sq.in. on one side of the 12x21 sheet comes out to about a 9.52% plated area). From all this, there are 86.5g Au, 558g Cu, and 80g Ni. The total of all three is 724.5g and the total of the Cu and Ni is 638g.

Theoretically, it would take 2.66 liters of 70% nitric to dissolve all of the Cu + Ni and it would take 3.02 liters of 4:1 AR to dissolve everything.

I still don't think that anyone knows the best way to run this stuff. We have come up with quite a few options. They would probably all work but some would work better than others.

The more I think about this, the more I think that the material is best left in sheet form and not shredded. I know that this will take more handling but, if you use nitric or HCl/H2O2 to dissolve the Cu/Ni, the loose foils would be easier to remove from the sheets than from the shredded material. If you used AR or HCl/bleach to dissolve everything, the sheets would be easier to rinse than shredded material.

It sounds like the HCl/H2O2 is sort of working for you in what you've done so far. One good thing about this solution is that it's cheap and, since it's only dissolving the Ni and Cu, you can use quite a bit of it.

How to run more than 1 sheet at a time - thinking out loud department. What if you had a 5 gallon bucket and a 3 gallon bucket (with maybe a dozen 1/2" holes drilled around the sides and 3 or 4 on the bottom), that fit inside of the 5 gal bucket? The sheets could be cut in half (into 6" x 21" pieces), a few plastic paper clips put every 3", or so, on the top, bottom, and end edges of each sheet to act as sort-of spacers, and then the sheets could be curved around the inside of the inner bucket - it shouldn't make much difference if they overlap on the ends. You could probably put quite a few sheets in there at one time. The inner bucket should have a plastic handle so it wouldn't get eaten by the acid. You could normally keep a lid on it and then, occasionally, lift the inner bucket up (slowly!) to drain and then put it back it. As you brought the bucket in and out several times, you would surely get solution flow between each sheet and agitation always improves the reaction rate. The only thing making the sheets stick together is surface tension. This would be broken easily, I would think, by the solution flow. I would imagine the plastic paper clips are PE (same as the buckets) and wouldn't be affected by the acid. It would probably take about 3 gal of acid to cover the sheets. 

I would suggest trying this on a very small scale using smaller strips of material. Just use a couple of small plastic containers. I would first try HCl/H2O2. If that works, you may be home free.

This could be done with nitric or HCl/H2O2. If using nitric, I would set the outer bucket in a plastic tray in case of foamovers. I would think that nitric would be much faster.

All of this assumes that the acid will penetrate through the gold and will dissolve 100% of the Ni/Cu. If it doesn't, you will probably have to consider dissolving all of the metal with AR or HCl/bleach.

I would bet that lazersteve has some suggestions on how to best use the HCl/H2O2 in this application.


*OR*, maybe you could just use two gallons of AR in the outer bucket and cut the sheets in thirds (4"), the long way, using the same 2-bucket/paper clip system as above. I would think this would be the fastest way, by far. Also, you wouldn't have to screw with collecting the foils. As Oz said, use only enough nitric as necessary and you won't have to evaporate.


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## goldsilverpro (Sep 12, 2010)

joem said:


> could you not just use an electric drill or dremel with a wire brush wheel to get the layer of gold off, and a vacuum to collect. This would minimize the amount of metal to deal with when processing.
> my thought


I originally thought of something similar but rejected it - using a small orbital sander with a dust bag on it. However, I have been involved with several of those catch-the-dust things and there usually are losses.


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## FrugalEE (Sep 12, 2010)

Joem,

I'm in final stage of cleaning up and I can't believe how hard it is to get all the tiny flakes coralled. I've decided that I better stop pushing around on loose pads with a stick and just use the squirt bottle to keep pieces as large as possible.

I think your abrasive technique would loose a lot of gold that you could never get out of your vac or brush. The goal is to get scattered gold(thin runs) that may be contaminated back into a large pure piece. There may be a place for abrasive techniques, but I would do it in a closed tumbler jar set up like a rock hound uses. I expect that would make some pretty fine dust that would almost have to be dissolved chemically or in an oven to avoid a torch blowing it all over.

Wire brushing my boards off sounds like an extreme amount of work and right now the chemistry sounds like a whole lot more fun.

It's time to get some drying action on my first gold pile and then respond to GSPs fine post.

FrugalEE


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## FrugalEE (Sep 12, 2010)

GSP,

I certainly am enjoying this project as well and am glad it has peaked your interest. It's got my problem solving juices going again and I've given up TV and find it hard to shut my mind off when it's time to sleep.

As to what kind of fumes I can tolerate lets just say I have access to a pretty isolated country place.

You mentioned bending around in a circle. These thin boards probably handle best that way as it gives them ridgidity. Your description needs further study on my part, but I'm visualizing concentric circles. 

The plastic paper clips sounds like an excellant idea, but they like all other spacers are going to mask out something. These boards have a .050 inch wide border all the way around them. This is less of a problem if the boards etch pretty fast as the clips can be moved or just accept the loss. This fixturing can all be worked out using only nice safe water.

I was also thinking of rigging up a rectangular card cage arrangement and that would probably work well in a plastic storage bin for the acid. The boards would have to be cut into something like 6 X 6 pieces to get any kind of ridgidity. 

I noticed today that it is convienent to hang up individual sheets to dry as there are lots of bolt & contact holes to use. 

My foils are nearly dry.

I too was looking forward to Lazer Steve stopping by. I plan to order his silver video and some crucibles.

FrugalEE


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## qst42know (Sep 12, 2010)

If these boards bend easily could you make two parallel cuts a half inch apart and an inch or so long and bend the tab to keep them separated?


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## FrugalEE (Sep 12, 2010)

QST, Thanks. Slotting and bending should work with this stuff. This project just keeps getting better and better.

I dried my foils in our kitchen oven at warm setting which was enough to singe the edge of the filter paper.

RESULTS: I'm excited to announce that the reading I got on the collected foils is that the gold foils weigh 0.85 grams. (The scale toggles between 0.8 and 0.9.) The predicted amount based on minimum gold thickness of 50 microns was 0.76 grams. 


Sources of error:

1. The scale is a $12 digital one I got at Harbor Freight & has only 0.1 gram resolution.

2. I'm doing some more drying to see if I got all the water

3. I used a different filter than the one containing the gold for tare

4. I'm sure there is gold left in the solution and also there are purplish black stains in the dishpan that don't want to come out easily. 

5. I only washed the gold a little and didn't bother to treat with HCL so that is another possible way to come up on the high side.

Conclusions: The 50 micron min. spec was met and then some and this material is definitely worthwhile to process.

I've taken some pictures and I'll edit and try to post them later this evening.

FrugalEE


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## Barren Realms 007 (Sep 12, 2010)

Make a dilute solution of AR and see if it takes the stain out.


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## goldsilverpro (Sep 12, 2010)

FrugalEE,

If you can, please post some photos of the original material. Even a scanner would work.

Don't you love it?

Chris


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## FrugalEE (Sep 12, 2010)

This should document what I've done in the past few days. Putting photos on the forum looks easier than I thought it might be, but I just looked and saw they got truncated so I've got to limit the vertical dimension a bit more. I belive I read someone say 600 pixels max. I also see the first one submitted ends up at the bottom and I intended the reverse order.

This sort of closes this phase of the project and I've got to give it a rest now and get some other things done while we have nice fall weather. I'll be reading your responses until early tomorrow, but for the rest of the week I won't be able to read or respond. I'll definitely be back to the forum & will begin the next phase after that.

Many thanks for all the good responses so far,

FrugalEE


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## FrugalEE (Oct 11, 2010)

Update: Oz agreed to do a test with nitric acid so I sent him a board and I got a detailed report with status every 10 minutes. With 25% nitric all the foils were free in 2 hours and with 50% nitric it took an hour.(I suspect that every time you cut the strength in half the time to etch doubles.) With that results I went and bought a gallon nitric as soon as I could. Following up on GSP's post of Nov. 4, 2009 I went to Terrace Packaging in Kansas City, MO and bought a gallon for $16.50 plus tax. 

Oz also warned me to avoid using any water that might have chlorine in it so I bought a gallon of distilled and the rest I'm using water from our dehumidifier. This way I don't have to worry if a batch is left in a long time about dissolving any gold.

Set up for Volume: In previous posts we have determined that about 1/2 gallon of acid would do a 100+ boards. In order to get enough volume for any kind of production I went ahead and mixed the 1/2 gallon of 67% nitric with 5 quarts of water. I put this in a 5 gallon pail. The boards to be etched are put in a 2 gallon pail which I have drilled holes similar to Steve's AP video set up. As of this writing I have etched 30 boards mostly 4 at a time. To prepare the 6 mil thick 12 X 21 inch board I fold it in half so that I have a piece 6 by 21 inches. I then cut it into 4 equal pieces. I then stack those pieces rotating each added piece 90 degrees. That gives me a pretty even stack with enough space for the acid to get to all surfaces. For the most part I don't aggitate at all, but sometimes rock the outer 5 gallon pail a bit if I'm in the area. It takes about 6 to 8 hours for a batch to completely etch. Sometimes I have a few pads still stuck on and I cut those out and run them in another small set up.

I'm sure the set up could be improved a bit more by having a smaller outer container so fluid would rise higher, but I'm getting the job done and accumulating a nice batch of gold spaghetti in a caserole dish.

Fumes: I'm running this in the garage near the door and open the door occassionally. I am not getting noticable brown NO2 fumes and it's only when I take the lid off to change the batch that the odor is real bad. In some earlier small scale work on my work bench I rusted a couple of tools.

FrugalEE


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## nickvc (Oct 12, 2010)

Way to go....I agree with GSP this is what refining is all about working out a way to get your values in an economical and simple repeatable way. The maths by GSP I'm sure are right as your experiment proved so you will have around $4000 worth of gold or better still a nice button.....be aware this can become addictive 8)


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## goldsilverpro (Oct 12, 2010)

FrugalEE,

Just remember that you won't know exactly how much gold you have until you refine the foils. Just weighing the foils might be misleading. Also, my prediction was based on the gold thickness you initially provided. 50 millionths (not 50 microns) has always seemed somewhat high to me but, who knows?


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## FrugalEE (Oct 12, 2010)

As GSP has pointed out I have wrongly used the term micron in some of my posts above. A micron is a millionth of a meter and not a millionth of an inch. I have always thought in terms of millionths of an inch.

FrugalEE


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## goldsilverpro (Oct 12, 2010)

FrugalEE said:


> As GSP has pointed out I have wrongly used the term micron in some of my posts above. A micron is a millionth of a meter and not a millionth of an inch. I have always thought in terms of millionths of an inch.
> 
> FrugalEE



One micron is 40 millionths of an inch (40 microinches) = .000040".


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## FrugalEE (Nov 17, 2010)

It's probably long past time for an update. I have continued to process the 12 X 21 inch boards as stated above, mostly on weekends using the original 2 qts of nitric to 5 qts of water. On Nov 2 after processing about 90 boards time to etch was getting to about 4 days so I added another quart of concentrated nitric and that got me back to something like 24 hour etch time. I now have processed 131 boards have the equivalent of 37 to go, plus I have 6 in solution that are taking a long time to finish. A few days ago I added 2 more quarts of water thinking that the solution might be getting saturated with Cu and Ni, but I don't think that helped. I also added some heat and not sure that helped much either. I have to admit that I'm also taking incomplely etched boards, cutting out the portions with gold still hanging on and etching them separately in a stronger solution.

When the ones in solution are finished I will have dissolved about 677 grams of Cu and 96 grams of Ni for a total of 773 grams of base metals. GSP's numbers of 120 grams of Cu per liter of 50/50 project that my 3 qts (2.85 liters) of nitric should dissolve 684 grams of Cu. That is awfully close to my 677 grams plus I've gotten the 96 grams of Ni as a bonus.

Any suggestions/comments? It looks like it's time to retire this solution or add some more fresh nitric. I'm hesitant to do that as I wanted to save some for misc. small projects without having another whole gallon around, but I'm into this deep enough that I'll probably use another gallon.

I started a new CuCL2 etch going yesterday. It is not exactly AP precause I didn't use any Peroxide. Instead I used only HCl that I washed some corroded copper in. I'm using a bubbler and it's pretty well etched in 24 hours. I may do the rest of the boards in CuCL2 etch.

I also took another look at GSP's post on AR above in this thread plus today's post where Oz dripped in nitric to really pin down nitric needed per unit of gold. I now realize it would have been much more efficient in nitric use to go directly to AR, but would gold dropped from a solution heavy in Cu and Ni have produced fine enough gold? I don't think so from what I've learned on this forum.

Another factor. Some of the boards got a bit contaminated with rodent urine and I suppose that contains some salt and Cl ions so I may have had a bit of gold dissolved.

FrugalEE


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## nickvc (Nov 18, 2010)

Nice job.
If you think you have some gold in your solutions you can test with stannous to confirm.
If you have add some copper sheet,if the acid is spent add a touch more and that should cement out any gold which you can add to your foils.
If you don't want any more nitric and your happy using hydrochloric to strip the foils you can also use it mixed with bleach,Chlorox,to dissolve your gold foils and complete your refining.


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## Harold_V (Nov 18, 2010)

FrugalEE said:


> Another factor. Some of the boards got a bit contaminated with rodent urine and I suppose that contains some salt and Cl ions so I may have had a bit of gold dissolved.


I expect not. So long as there's any base metal present, even if traces of gold go in to solution, they are immediately cemented by the base metal. Of course, it will no longer resemble gold as you know it, but will be found in the bottom in the way of a dark brown to black powder. I suggest you collect all solids that come from the solutions from this project and process for values. 

Harold


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## FrugalEE (Nov 18, 2010)

Nickvc,

Thanks. I did poke a piece of copper into my wash water the other day to see if I would get gold or possibly something else not considered and it just got shinier. The same thing would happen if I put it in the main etch tank. See Harold's comment. I think I will be processing these foils in a variety of ways including the HCL/Clorox method to gain the experience. This is far more about the learning than trying to make money. I still haven't mixed the stannous chloride and played with it yet. I'm lookng for a decent eye dropper & bottle combination among my junk.

Harold,

You're right of course about the base metals, copper and nickel cementing out the gold. I was looking at my copy of that series yesterday, but it never dawned on me how it applied to my main etching operation.

I have to admit that I have no idea yet what the bottom of that pail looks like, but I'll sure process it just like the foils. I expect it wouldn't have quite the purity that the foils have. There may be some base metal sticking to the gold that came out, but if exposed it should redissolve when the pail is agitated.

This little fail safe makes nitric even more of a process that insures you can always see your gold in solid form.

Thanks,

FrugalEE


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## Harold_V (Nov 19, 2010)

FrugalEE said:


> I have to admit that I have no idea yet what the bottom of that pail looks like, but I'll sure process it just like the foils. I expect it wouldn't have quite the purity that the foils have. There may be some base metal sticking to the gold that came out, but if exposed it should redissolve when the pail is agitated.


My typical procedure with such material would be to incinerate, then screen, crushing any solids, using a mortar and pestle. I would then give the residue a wash in hot HCl, then a couple rinses with tap water. Only then would I attempt to dissolve the values. Nothing like it for yielding a gold chloride solution that is easy to filter, and free of contaminants. 

Harold


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## FrugalEE (Nov 19, 2010)

Thanks Harold,

Most of the material was pretty clean, but I'm sure there are a few rodent hairs and some other non gold crud in there, so I'll process it as you suggested.

FrugalEE


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## Harold_V (Nov 20, 2010)

I can say with total honesty, nothing got processed in my system without first being heated enough to eliminate carbon. I think you'll find that a considerable amount of rubbish will be eliminated from your material. Much more than rodent hair!  Your reward will be much cleaner gold, and easier filtration. 

Harold


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## FrugalEE (Feb 12, 2011)

Subject: Long reaction time

Just before the start of October 2010 I put a test sample piece of my teflon fiberglass board in a test tube with what was labeled 2% nitric acid. It wasn't until the end of January that I noticed that the run had finally come loose. That's 4 months! That donut island takes quite a bit longer. This material had .0007 inch thick copper with .0001 nickel and gold plated at 50 millionths of an inch and up.

FrugalEE


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