# Mixing foils



## haveagojoe (Mar 29, 2017)

Hi folks,
I am preparing to do my first refine of foils I have collected from escrap. I have 3 modest batches in storage jars in water. One is relatively clean, from cleanish boards and fingers. The other two smaller batches are from sources containing solder and other base metal contaminants. I intend to dissolve them with the bleach method, drop the lead out with sulphuric, filter and drop with copperas. Before I dissolve them each jar separately will be roasted and then soaked in HCl to clean up residual oxides. 
My question is, what are peoples opinions about combining the foils before dissolving, so that I only have to do one drop, or should I dissolve them separately and do 3 separate drops?


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## kernels (Mar 29, 2017)

What process did you follow to recover the foils ?


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## kurtak (Mar 29, 2017)

haveagojoe

As long as you are going to roast them & do a HCl treatment prior to dissolving the foils (for the refining) there is no reason to do them as separate batch's

Do them as one batch & make it worth while

Kurt


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## haveagojoe (Mar 29, 2017)

kernels, these are all from AP, which I do in numerous separate batches and then combine foils from the same types of sources, keeping solder free stuff separate up to this point.

kurtak, thanks yes that's what I was thinking, I have roasted one of the smaller batches and after a soak in HCl they came up looking so clean and sparkly they look better than the batch from clean boards, so I reckon I'll go for it. All the eggs in one basket


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## kernels (Mar 29, 2017)

If you used AP to recover the foils, all the solder will already have been dissolved ? I would generally tend to try and run larger batches at a time, your losses (in things like filters) are smaller for larger batches. But only if the material going in is basically the same.

Obviously if you are trying to do some comparisons between the yields for RAM vs. PCI cards for instance, then you can't combine anything.


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## haveagojoe (Mar 29, 2017)

In theory, yes, but the foils from batches where the source material contained solder are visibly more contaminated than those from clean fingers. Specifically a fine black powder which I think is silver, which got dissolved then dropped out onto copper parts of the source material. Roasting and then soaking in HCl did a great job of removing this but I wonder about other contaminants which may not be visible.


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## kernels (Mar 29, 2017)

Your only risk is that contaminated batches somehow complicate the refining of the clean batches ? I've been at this hobby for a while, so that wouldn't concern me too much, in the end if your process is robust you will end up with reasonably pure gold. Depending on your personal level of experience, you may wish to process them separately just to see the results before deciding whether to mix them next time or not.

I would probably not bother roasting and the HCl soaking foils, but then I don't get foils from items that also have solder. If there is solder present, then the foils are probably ENIG and more hassle to recover than the gold is worth. Where did the contaminated foils come from ?


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## kurtak (Mar 30, 2017)

haveagojoe

If you are going to roast the foils from each batch then do a HCl treatment of each foil batch before dissolving them all together as one refine --- there don't mess around roasting & HCl treating each (foil) batch separately

Put ALL the foils together - roast them ALL together - HCl treat them ALL together - then filter/wash them ALL together & dissolve for the refine 

In other words - if you are going to refine them as one batch - there is no sense in cleaning them up in separate batch's --- clean them up as one batch also

Edit to add; -


> In theory, yes, but the foils from batches where the source material contained solder are visibly more contaminated than those from clean fingers. Specifically a fine black powder which I think is silver, which got dissolved then dropped out onto copper parts of the source material. Roasting and then soaking in HCl did a great job of removing this but I wonder about other contaminants which may not be visible.



Per the underlined - It is for this very reason that I highly recommend ALWAYS roasting foils & doing a HCL treatment to foils before refining them - its a simple step - AND - it "insures" a clean(er) refine 

Harold gave this advice "often" --- it is advise I took to heart when I first joined the forum & have followed ever sense 

If you don't roast & HCL treat your foils before refining - try it - you will be surprised just how contaminated foils that "appear" to be clean can actually be 

Kurt


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## kurtak (Mar 30, 2017)

kernels said:


> Your only risk is that contaminated batches somehow complicate the refining of the clean batches ? quote]
> 
> That the whole reason behind roasting & treating with HCl prior to refining - to clean the foils up so the refine is less complicated
> 
> ...



Not sure where you get this idea from - but I have processed material that had solder associated with it that has run as high as 3 grams gold per pound of starting base material 

Kurt


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## haveagojoe (Mar 30, 2017)

Thanks guys, 
Yes Kurt I am following the advice Harold gave, and having roasted and soaked one of the batches I can see the value of doing so very clearly. To my mind, removing as much of the unwanted stuff as early on as possible in the process is the ideal approach, to minimise the contaminants in the final dissolve and reduce the amount of drag-down in the drop. And yes you are right, it makes more sense to combine the foils before roasting and soaking rather than doing that stage in separate batches. 
Kernels the solder-contaminated material comes from many different sources- mobile phones, laptops, pins and links from many kinds of connectors etc. Since I collected those foils I have learned about pre-soaking boards etc in plain HCl to remove solder, so that's what I do now to get rid of it early. I will still roast the foils and use HCl again before the dissolving stage. Like I said, to me it makes sense to do everything I can as early as I can in the process.


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## kernels (Mar 30, 2017)

kurtak said:


> kernels said:
> 
> 
> > Your only risk is that contaminated batches somehow complicate the refining of the clean batches ? quote]
> ...



I get this idea from hard gold being difficult to solder to in manufacturing, so any electronics made in the last 30 years or does not use hard gold plating over the entire PCBs. If you trim gold fingers correctly you shouldn't have solder. Usually inexperienced people who want to AP whole boards (with solder) are either chasing the ENIG from those cell-tower typer boards (waste of time, I have tried) or from the gold 'plating' under the solder mask on some sound cards or mobile phone boards. Once again there is not really much gold there. But at the same time I do realize that there are some boards that are fully hard-gold plated. 

Do you recall which type of boards were giving you 6g/kg ? That sounds amazing, vintage test gear ?


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## snoman701 (Mar 30, 2017)

What is ENIG?


Sent from my iPhone using Tapatalk


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## kernels (Mar 30, 2017)

https://en.wikipedia.org/wiki/Electroless_nickel_immersion_gold

2-8 μin Au over 120-240 μin Ni


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## glorycloud (Mar 30, 2017)

I'm sure that I have run at least 100 pounds of gold fingers so far in AP.
I've never roasted any foils yet, I have always just followed LaserSteve's
method for processing them and that pretty much just recommends multiple
soaks of the foils in HCL before using HCL / bleach.

The gold always seems to be pretty pure as I also do the recommended Au powder
wash procedures found here on the forum.


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## haveagojoe (Mar 31, 2017)

mmm those cookies look very tasty!


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## anachronism (Mar 31, 2017)

glorycloud said:


> I'm sure that I have run at least 100 pounds of gold fingers so far in AP.
> *I've never roasted any foils yet*, I have always just followed LaserSteve's
> method for processing them and that pretty much just recommends multiple
> soaks of the foils in HCL before using HCL / bleach.
> ...



I completely agree with you Glory. I've never roasted them either - good cleaning is good enough. You either clean them before you dissolve or after there's no getting away with it whichever way round you do it. 

Jon


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## patnor1011 (Mar 31, 2017)

It probably depend on how much time do you have. I usually do have plenty so all my foils along with some debris go to jar half full of HCl. I do give it occasional swirl once a day or whenever I am around. I do keep them there sometimes week or two sometimes even longer. I tend to process when I accumulate more so they get cleaned while waiting for more to add. If you are in a rush perhaps warm HCl may do the job faster.


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