# I need a little clarification



## Silver Handle (Nov 8, 2011)

Ok so I will try to not come of as sounding to noobish here. I have read til my eyes hurt and I think I am ready to get some shopping done,I Just need a few finer points defined.
Over the years I have hoarded my e-scrap and I am ready to start refining it. I plan to try and get the most from my scrap by separating, things like flatpacks and monolith caps. Pretty much for the first go around I am planning only chasing the silver and gold and just hoarding the caps for later. 
Coming into the forum I was aware of AR. Upon reading I have discovered there are several process to refining out PM's, including AP.
So my questions are this: Is it just personal preference which process/'es are used? Are there advantages to a nitric bath followed by AP as opposed to just AR when trying to refine both silver and gold? Have I simply not read enough,or possibly overlooked this through my bloodshot eyes? Any and All help is always appreciated.

Thanks for looking
-SH


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## Acid_Bath76 (Nov 8, 2011)

SH, 

Welcome to the GRF. I think before you start, you should maybe post a pic of exactly what it is you want to process. You're right in dissolving the base metals first. Remember though, if you start with nitric, you're going to want to incinerate your material after using it before switching to another method other than AR. If you use nitric to dissolve the base metals, and then switch over to something like AP you're going to have problems. Even a little bit of nitric that you weren't able to wash off is going to react with the HCL. You've just involuntarily created AR. Remember, it only takes around 1mL Nitric and 4mL of HCL to dissolve 1g of gold. That's a teardrop of Nitric. More than enough to slip by and ruin your day. If this your first run, I would start with something like the gold foil fingers on RAM. I would also reread HOKE. You can't absorb that book in one pass. Check out Lazersteve's video's on fingers. Seriously, reading and seeing someone go through the steps is a huge help. It was for me. Good luck, and be safe!


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## element47 (Nov 8, 2011)

The process used is chosen on a decision hierarchy of (not necessarily in order of importance) 1: Which chemicals are least expensive and most available 2: Which processes have superior effect & yield 3: which type of feedstock is being refined 4: which process has the best documentation and experience notes from members and HOKE. 

Most folks want to use hydrochloric acid before nitric, as HCl is much cheaper. They also want to use Sulfuric acid before nitric, same reason. Users want to get rid of as much and as many junk metals as possible so that careful refining can be applied to only one or at most, two metals, and in the least quantity possible so as to conserve more valuable chemicals. When you are dissolving the fingers from PC boards, you are looking to undercut the gold plating on the fingers, really not touch the gold (chemically) at all, but to dissolve the copper and solder-type materials that underlie them. The process of dissolving those thinly-deposited (junk) metals releases the gold plate foils above them, leaving the foils as a fairly coherent item. The process of deplating gold-plated pins is different, because the acid-solvents cannot get to the interior of the pins so effectively, and the *relative* amounts of junk metal and gold are a lot different than they are on PC board fingers. At the same time, with the reverse electroplating method, advantage is taken that the pins, all jumbled on top of each other, will conduct electricity. That cannot be said about "finger trimmings" from PC boards. 

Users do NOT use AR first because the general flow of things is to get rid of junk metals BEFORE dissolving gold. In other words, advantage is being taken that gold will NOT dissolve in the first things we soak our materials in. So, HCl or H2SO4 or H2SO4 + electricity are used earlier to get rid of as much crap, using the cheapest chemicals as possible. Then, the remaining gold is refined without the interference of undesired metals. AR dissolves almost everything. Silver chloride is very insoluble and also interferes with more delicate techniques, so generally we want to have HCl going first, make our chloride reactions, wash out/get rid of the reactive chlorides. For the same reason, we do not want to use tap water on silver because there is chlorine in that water. With gold, it doesn't matter. 

Lastly, the process used to refine gold are quite different from those used for silver. Not only are the metals generally not found together in the same item, but the processes are different. The non-guru folks around here who go from interested students to refining success resolutely shun innovation and look to duplicate processes that have been proven successful. This isn't an inventing challenge, quite the opposite. The challenge is to carefully follow the known-to-work procedures with no wrong turns, understanding the process(es) at each step of the way, knowing what should be the result of the next thing you are contemplating and with saint-like patience and discipline. And trying out small batches before throwing your whole pile into a 5 gallon bucket of evil liquid.


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## Silver Handle (Nov 8, 2011)

Thanks to both of you for such a quick reply. I get it now. I was of the opinion from what I read that made me think, Hmm why not just put all of my scrap in a five gallon bucket, remove the silver with nitric, then the gold using AR process. I see now the flaw in that thought process. I will get some pictures up, when I get everything separated and categorized. I will start with the fingers to "get my feet wet" as it were as suggested.


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## Acid_Bath76 (Nov 9, 2011)

If you're just getting into this, fingers are a great place to start.... AFTER you've read. You're able to see your gold throughout the process, and you can reuse the acid once you've finished. In the event that the AP (HCL & H202, 4:1)dissolves a little, not to worry. As the solution becomes saturated with copper(after a couple uses), it will displace the dissolved gold. One process can teach you a lot. Just take it slow and be safe. 
One thing I wish I had done my first time around with fingers in AP, is using a bubbler. You can get a cheap $5 aquarium bubbler from walmart. When your AP is sitting, the bubbles will continue to introduce 02 to the reaction. The hydrogen peroxide is just a jump start, and won't last long. If you're able to agitate every ten minutes or so, you can have this done easily in a day. There are a crazy amount of posts on processing fingers, so do a little searching and you should be more than taken care of. There's no hurry, well I hope there isn't, so don't start until you think you know exactly how this will unfold. Consider what could go wrong. Have contingencies and "problem solve" before you jump into this. I find this brings up more questions, and helps me resolve a potential problem before it even comes up. Good luck, and be safe.


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## wrecker45 (Nov 9, 2011)

i just put fingers in a slow cooker on medium heat with hcl . it takes about 3 days to get the foils off. then i pour everything into a plastic spagetie strainer over a 5 gallon pail and rince with water.


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## niteliteone (Nov 9, 2011)

wrecker45 said:


> i just put fingers in a slow cooker on medium heat with hcl . it takes about 3 days to get the foils off. then i pour everything into a plastic spagetie strainer over a 5 gallon pail and rince with water.



Be sure to put a couple of coffee filters into the spaghetti strainer first.

Tom C.


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## artart47 (Nov 9, 2011)

Hi there Silverhandle!
I just thought I'de throw something in for you . You get going and are doing your different processes and all your hard work and considerable values are there in front of you in this flask! Man, no more than two hours ago, mine broke while I was heating it, the bottom just craked and the jar tipped sideways a little, all the contents poured out...
I'm new to this but, I alway have some kind of containment devise that will catch my treasure in case of a mishap! I had perhaps 5grams of Au. in a mix of now base metal-free powder from plated pins in Hcl. powder is whats left of the plastic connectors that held the pins,It was the final wash with boiling water before it goes in with my other Au. awaiting HCl/Chlorox.
I have a month of anticipation and quite a bit of work in that jar. I can't imagine the heartbreak if I had seen it running down into the stove and on the floor! fortunatly I had it in a water bath that caught everything and as I type it is filtering in my shop! No losses!
Don't forget to give some thought to making you work area so that you don't loose values if something goes wrong. If you store a jar of AuCl, keep it in a bucket , etc... ( <----- thanks Herold, )
Good luck looking forward to seeing your first gold!


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## niteliteone (Nov 9, 2011)

artart47
good post and a great recovery too. 
Were you using a heat resistant beaker or flask when this happened? 
Tom C


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## artart47 (Nov 9, 2011)

Hi!
No, I was just using real large mason l
jars for the water baths.
there was no thermal shock or anything ,It was up to almost a simmer and I just heard a pop and it turned alittle sideways!
As I get extra money I'll get lab quality stuff, but for now I gotta make due with what I have.


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## niteliteone (Nov 9, 2011)

Been their, done that myself.
Luckily I haven't lost any values either.
Here is a site that has good prices on some of the starter items (glassware) I have purchased. No minimums and great service.
http://www.homesciencetools.com/

Tom C.


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## Palladium (Nov 9, 2011)

I've went through a lottt of mason jars. I have two that i'm fond of. Other than that I've had them break in almost every situation you can think of. I had one i left sitting on my counter top and left for a little while. Empty i might add, not heated, nothing. When i came back a couple of hours later and picked it up it had broken right around that bottom lip where the sides end and the bottom starts. I kid you not! Still haven't figured that one out yet. Now that i have gotten just a little more serious about things i bought some Griffin beakers and some pyroceram dishes. For the cost of 1-2 grams of gold its one of the best investments you can make. Man what a difference and a peace of mind it makes. Thank you Pyrex, thank you Corning, and god bless the Gold Refining Forum.com


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## artart47 (Nov 10, 2011)

WOW!
That's just how mine broke! right around the bottom where it curves and there is a little rise on one side. I can't understand it. I've been using Mason jars for fourty years for canning, heated them in water baths, pressure cooker, never had one crack! 
It's like Murphy's law at work. If it's going to break, it'll wait till you fill it with something of extreem value.


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## Silver Handle (Nov 14, 2011)

Wow. thanks for all the tips guys. I ordered some equipment from home science tools, and began harvesting. I didn't have as many fingers as I thought I did. only about 50 grams. I did find a couple of nice ones that I have some questions about which direction to proceed next. First though picture of my fingers.






I found one ram stick that had gold plated traces everywhere I found out how to remove the solder mask thanks to the forum and the search button  





I also found this really nice card that appears to be all gold beneath the solder mask . Traces, pads, the works. My question is, how do remove the pins, caps, etc without incinerating the board and messing up all that gold? Is hand de-soldering the only option?





As always any and all tips appreciated and thanks for looking. :wink: 

-SH


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## Geo (Nov 14, 2011)

Silver Handle said:


> Wow. thanks for all the tips guys. I ordered some equipment from home science tools, and began harvesting. I didn't have as many fingers as I thought I did. only about 50 grams. I did find a couple of nice ones that I have some questions about which direction to proceed next. First though picture of my fingers.
> As always any and all tips appreciated and thanks for looking. :wink:
> -SH



be sure to check all sound cards and video cards.for some reason the biggest majority of these will be gold plated on all metal traces.depopulate all boards(remove the components) and remove the solder mask with caustic soda bath and then put it all in AP.


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## philddreamer (Nov 14, 2011)

Yeap, especially those sound blasters! :mrgreen:


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## artart47 (Nov 15, 2011)

I've got a stack of sound blasters (already did the fingers) waiting to be processed!

Silverhandle! 
I was all excited when I first came to our forum. I was all set to just pulling gold out of all the stuff I had collected. I spent a long time reading and learning about reclaiming and refining the values that are in electronics. I saw all kinds of people coming here with a bucket of disaster asking for help! You may be excited about your new interest, but, you now know enough to be dangerous!
If you watch one of Lazersteve's videos, you see how organized he is, safety precautions, He knows what he's doing and what's going on in the reaction vessel. 
You need to start with simple and small batches before thinking about doing cards,lye solutions and such until you learn more and get experience actually working with the stuff! Doing the fingers from your cards in AP is a good start. Then how to clean your foils of any base metals, How to melt them....hold the button in your hand!
The quest is to learn refining! Then you can safely enjoy you new hobby of getting the gold out.
good luck!


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## Silver Handle (Nov 15, 2011)

Thanks again guys. I love all the new friends I am making, and the knowledge I am acquiring. I found the depopulation thread finally. Thanks to Geo. Sometimes its all about knowing the right search term to use.

Artart. Just for clarification sake: I was already dangerous before I came here!  I have watched most of Steve's videos, most of them more than once already. BTW my acid gas respirator and splash guard goggles came in yesterday. Just so you know, I too am all about safety first. 

Personally I thought stripping a solder mask with lye would be easier than dealing with acids, as I used to help my grandma make soap. Plus I figured I could add that card to my fingers. I started with the whole thing in a cookie jar, that cracked in the process from the heat. I had my safety plate in place, so no worries. I had to then transfer my solution to a smaller dish, and cut the board down in order to finish processing. It came out fairly well in my opinion.






I also discovered something in the process. After needing to remove the solution and card from the heat, and then replacing it to the heat I noticed the mask came directly off with no washing. I repeated this with the second part of the card by heating within the solution, removing from heat, then reheating, All I had to do was remove the card and rinse. no rubbing involved in removing the mask. I did rub it to make sure I had removed all the caustic though.


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## artart47 (Nov 19, 2011)

cool! happy havesting! Neat discovery, I'll try that on my next batch.
The lye solution always seems to disolve some surface gold, same as my AP for cell boards. I did some search for dropping gold from lye but didn't find anything. Did you seem to loose to the solution too?
Later!


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## Silver Handle (Nov 19, 2011)

Funny you should ask. the lye did lighten the color somewhat. Then I ran my harvest through AP but I see no gold. still trying to figure out what I did wrong. It looked just like Steve's video until I started to pour it through the filter. all was left is black sand. I saw in his video that might be my gold dissolved and re-precipitated back out.

I am stuck now. I have this dust mixed with some solder mask, with all of about 6 foils. I dont want to proceed to the next step with just the dust with out some advice from the gurus.

Anyone?


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## niteliteone (Nov 19, 2011)

You did nothing wrong. But from what I see, the boards from the pictures only have gold on the fingers, a few test points and some thru holes.

If memory is right it was the "Sound Blaster GOLD" that had plated traces. Most of the others only have plated fingers, test points and some thru holes.

Tom C.


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## Silver Handle (Nov 19, 2011)

ok now I am even more confused. I made some stannous chloride and did a swab test. It would seem the sand has virtually no gold whatsoever, but my Ap solution is saturated with it. Any suggestions? Can I drop gold from Ap?


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## Geo (Nov 19, 2011)

yes. filter the solution to remove all solids and precipitate gold with SMB.


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## artart47 (Nov 19, 2011)

Hi!
I kind of think I read someplace here that if you heat the lye solution it will disolve gold that is thin. Seem to remember they were warning someone not to heat it. The next batch I'm going to start very weak and keep uping the consentration till it begins attacking the mask. I'd like to hear from anyone who has dropped gold from lye .
My cell phone boards came out with about a third of the very thin gold gone. I only processed about a hundred boards and a couple dozen telecom boards that have the little gold spots under where the push buttons are. That's just a very small amount of gold and you probably wouldn't be able to see it if you dropped it. I'm going to just keep using the solution and eventually it will have enogh gold to work with.


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## niteliteone (Nov 19, 2011)

artart47 said:


> Hi!
> I kind of think I read someplace here that if you heat the lye solution it will disolve gold that is thin. Seem to remember they were warning someone not to heat it. The next batch I'm going to start very weak and keep uping the consentration till it begins attacking the mask. I'd like to hear from anyone who has dropped gold from lye .
> My cell phone boards came out with about a third of the very thin gold gone. I only processed about a hundred boards and a couple dozen telecom boards that have the little gold spots under where the push buttons are. That's just a very small amount of gold and you probably wouldn't be able to see it if you dropped it. I'm going to just keep using the solution and eventually it will have enogh gold to work with.



Do a search on the forum reguarding the types of boards you are talking about. You will find out that these are low yield boards to begin with. Looks like more than their really is.

i don't know about the lye solution you are using, but I THINK that it takes acid to take gold into solution like you are talking about. 

I have processed a lot of cell phone boards and have never placed them into a lye solution to remove the mask, exposing the COPPER to be digested into solution. The gold has always been exposed and easy to set free with HCL/H202 for a full recovery. 
Just depopulate the boards and place them into the acid to remove the foils. No need to remove the solder mask unless you know for sure there is gold plating under it.

Tom C.


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## Geo (Nov 20, 2011)

ive never heard of lye dissolving gold.im not saying it hasnt happened but ive done the same process many times and never lost gold to lye.


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## Silver Handle (Nov 20, 2011)

I was always good in chemistry. Got straight A's, and typically I can usually follow directions to a Tee . With this being my first run and things not going according to how the directions are spelled out, I was a little flustered. I felt somewhat duped into trying a method that everyone here swears by. I felt I should have stuck to my guns and done a nitric bath followed by AR, that way when my gold dissolved, it would have been because I had expected it to.

Ok as much as I would rather read and hate being spoon fed, As I am way off the book here, I need to know what to do next. I have what I would assume to be a bright green Ap solution, with a white powder at the bottom. I know I need to siphon off the liquid,and dry the powder, but that's where it ends.

Next, what happened to my gold? After precipitating my Ap with SMB as directed and testing both precipitate and solution, my gold is now gone. WTH? Should I simply treat the entire batch as waste without bothering to siphon? 

It is true I don't fully understand the process, which is why I started small so I could learn. Hands on works really well for me.However when it takes an unexpected turn and no amount of searching provides any intel, I must say my faith in the AP process has been rocked.

I really wanted this to work. I convinced the little woman that this would work in order to get us some gold. There is no way she is going to let me keep spending money on this new hobby without some results. I fear without that I will have to abandon this before it even got a chance to get started.

As always any and all help appreciated, and thanks for looking.
-SH


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## ShaynePatrick (Nov 20, 2011)

Don't ever thow it out.
If you had gold, it's there somewhere.

Sometimes it can be a little frustrating to find. For instance, once I dissolved some gold in HCl + Cl, but my testing showed no gold. I knew it was there. What happened? My Cl concentration was WAY high and I had a false negative. If I'd thrown out the batch I would have lost three grams of gold (not a lot, but a lot to throw away in frustration).
Be patient, reach out to Harold, he was a HUGE help to me when I was kicking around the idea of using a sulfiric cell to deplate.

Save everything.
Mastery takes practice.

Also, there is a good piece in the forum about how to clean up you fluids prior to disposal. The most important thing to get out before disposal is Copper Chloride.


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## butcher (Nov 20, 2011)

Silver Handle, 
Next, what happened to my gold? After precipitating my Ap with SMB as directed and testing both precipitate and solution, my gold is now gone. WTH? Should I simply treat the entire batch as waste without bothering to siphon? 

Testing the solution (please explain your method)
Testing the precipitate. (Can you tell me how you are doing this?)
Give us some details of what you did to get to where you are now. Then maybe we can give better advice.
How much materials and what type, what acids or reagents, how they used, heat, and even details you think are not important may be.

Look these are very easy processes and if you are having trouble with these, then you would really have problems with nitric and aqua regia (a whole nother ball game).

Do not toss anything.

Looks like you are fairly new to this, do not get frustrated, cement your solution onto copper, and test your solution for values, treat the solution by reading dealing with wastes.

Tell your wife you have the gold and will get it into a form she will like but it takes time she needs to learn patience, as you do, (patience is one lesson will learn from refining).

Now get back to reading Hokes book, doing the chemical experiments she suggested, reading the forum, and studying, until you know where you went wrong and how to correct it, you understand how to run the process you choose know how and why it works, and how to fix things if it does not.

If you do not follow this advice I am afraid you will always be wondering where you lost all of that gold, until you do wise up and study.

Patience you will be melting beautiful buttons soon enough, but you must learn to walk before running.

Also spend time gathering materials you need (do not spend much money, until you are positive you need it (there is no free method, second hand store alternative, or you cannot build or make your own), do not use high grade materials to learn to do the process, or else you should expect high grade losses.

Welcome to the forum, I could hold your hand through some process, but you would not learn to do it without me holding your hand, you need the education and understanding to stand on yer own two feet and know what to do next in any circumstance you run into.

I hope you understand and this helps.


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## Geo (Nov 20, 2011)

this is something that a person should enjoy doing,i know i do.even my failures is a chance for me to learn,i know its not the preferred way to learn but learning non the less.if you are in a financial bind then this is not something you should start doing as a hobby and most assuredly not something to try and make a living with just starting out.the pressure for success takes the fun out of the experience.the first time i tried poor mans AR was on IC's and phone boards.i did everything exactly the way i was told to do it yet when it was done i tested the solution and it was negative.all the gold was removed and it wasnt in the solution.i evaporated the solution and let it cool and still nothing.i checked the stuff left over and the gold was gone.on a whim i added hcl to the stuff left over and then added a small amount of Cl.after the reaction stopped i tested and got an instant black test.the solution was loaded with gold.the AR was barren of gold.i can only assume the gold cemented out on the left over metals in my pot and i couldnt see it for the trash.all this happened over several days time with me racking my brain trying to figure out what i did wrong.your gold is there,somewhere,hiding from you.test,retest,precipitate,redissolve it will turn up as long as you dont throw it away.


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## alext_iwan (Nov 22, 2011)

hello all master... i am newbie in this forum...
happy when i see pic and read your success story... i want to do like you all..
who master in this forum can teaching me...
why my gold (low yield boards) disolve in the solder mask solution (steve video)...? :?:  :?: 
my board have gold but low yield content. this problem same as silver handle.. i do with 2 board. one full process and second with half process like number one.. (a few minutes ago)
now i have 2 board with number one looked nickel plate because gold was disolve and second board looked some gold not fully disolve..
i see silver handle picture with finger of soundblaster true disolve same as my problem.. :roll: 
how with true of step by step for stripping a solder mask? with heat or not? :?: 
if can't manage low gold content how with gold plate with high yield content in the solder mask solution your gold gone without you know... :| 

..sorry for my bad english language..


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## butcher (Nov 23, 2011)

alext_iwan,

Welcome to the forum.
Your English is hard for me to understand, but I cannot speak but one language (that one not well) , so I admire you learning two languages.

We would like to help you, but we also need to be able to understand the questions you ask.
I see you have Steve’s video, if I understand, Steve’s methods work very well, and if you follow them you should have very little trouble.
Laser Steve’s web site also has a very good search for what you want to learn from the forum.
You must understand why we do things and what happens when we do something, understanding the principles you will know what to do when you do have troubles.
Have you read C.M. Hoke's book, there is free download in book section.
This book will teach you the all of the basic principles of refining.

You should not try and recover gold from whole circuit boards.
Separate by hand the gold parts.
Treat each type of parts separate.
Remove base metals from gold, before trying to dissolve gold.

Read C.M. Hoke's book this is best way to learn.


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## alext_iwan (Nov 23, 2011)

butcher,

thanks for your answer, but you not understand..
i just want to remove soldermask... but the gold dissolve..  
why the gold dissolve..? just it i need to know.. how with the true process stripping soldermask without dissolving the gold..?
how to recover the gold from sodium hydroxide?


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## butcher (Nov 23, 2011)

alext_iwan,

I have never used sodium hydroxide to remove solder mask.

I really do not believe the NaOH would dissolve the gold under the conditions you are using.
But I do believe the gold plating can be so thin, and so little involved that the metals under gold can oxidize and (some of them go into solution) and the very small amount of gold could be in very fine powder mixed in this mess, making retrieving you gold somewhat difficult, I would try diluting and adding some HCl to get pH more neutral, let it settle well, decant the salt water and then treat residue.

Heat would be my choice for removing solder mask (or just breaking it down), not getting them so hot that the resin in boards melts, but just heating the surface enough to lift the adhesion of the solder mask and so the acids can attack metals under it.


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## Geo (Nov 23, 2011)

alext_iwan said:


> butcher,
> 
> thanks for your answer, but you not understand..
> i just want to remove soldermask... but the gold dissolve..
> ...



are you boiling the solution? you should not boil but heat just enough to be very warm to the touch.let the piece stay in solution for five minutes and test to see if the solder mask will come off,if not place back in solution for another five minutes and test again.


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## alext_iwan (Nov 24, 2011)

butcher,



> I really do not believe the NaOH would dissolve the gold



how with sodium aurate (NaAuO2)?

geo,



> are you boiling the solution?



just warm because my heater set to low. i dont know if much time enough to boil the solution.

thanks geo, i will try again. and sutoff my heater if enough warming the solution.


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## artart47 (Nov 24, 2011)

Alext.
I wrote the same thing, same thing happened to my gold. Some of the boards,the gold plate is so thin that it comes of in the sodium hydroxide. The boards come out with copper at the places where gold used to be. I scraped to see if may-be some copper was on top of the gold, gold is gone. I didn't heat the solution. Idid searches to try to find the simple answer... how to drop gold out of lye solution and can't find anything!
Everyone say's that lye doesn't disolve gold, because there is very little gold on those boards it will take hundreds of them to make alittle gold,so i will probably keep using the solution untill the is more gold and I eventually find the post that tells how to get it out or I find some way. Or may-be, somethingelse is going on, where the gold is in the solder mask sludge? I don'k know yet.


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## alext_iwan (Nov 24, 2011)

artart47,

i think sodium aurate (NaAuO2) is this problem.
but i'm not sure..


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## qst42know (Nov 24, 2011)

I expect your gold to be as an unrecognizable fine dust sitting on the bottom, being too thin to hold the form of visible foils.

I would rinse the solids, incinerate, and dissolve as usual.


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## Geo (Nov 24, 2011)

im of the same opinion.if you didnt toss the loose solder mask put it in a container and add hcl/cl then test with stannous and see if you get color.


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## butcher (Nov 24, 2011)

From what I understand the gold would have to have been already dissolved as a chloride, (as an ion, missing electron), for the hydroxide to form the sodium aurate, elemental gold metal is very resistant to oxidation, I believe even very thin gold would not oxidize easily. 

This is some of what I have read:

Gold dissolved in solutions of AuCl3 react with strong base NaOH and will precipitate gold hydroxide Au (OH) 3, .which can dissolve if excess NaOH is used, and apparently this will form sodium aurate (NaAuO2). If gently heated, Au (OH) 3 decomposes to an oxide of gold Au2O3, more heat then to gold metal.

click here


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## Geo (Nov 25, 2011)

so you can compound gold to almost any base by dissolving gold in AR and then adding the base thereby forming the salt of that base compounded with gold, Aurate.so if gold can be a sulfide in solution does that mean that im loosing gold in my stock pot unless i condense and incinerate everything in the pot?


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## artart47 (Nov 25, 2011)

Hay guys! happy thanksgiving and thanks for all your interest in this riddle!
I think you are right in that our gold is as unrecognizable powder, I kept everything and after thinking over you advise, I'll find it. I'll make sure to post whatever the results are. I am taking your idea about not removing the mask and exposing the copper. only some boards had gold under the mask.
Thanks again


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## butcher (Nov 25, 2011)

Geo,
"So you can compound gold to almost any base by dissolving gold in AR and then adding the base thereby forming the salt of that base compounded with gold, Aurate. So if gold can be a sulfide in solution does that mean that I am loosing gold in my stock pot unless i condense and incinerate everything in the pot?"

I do not know if I can answer your question, but until I get more education here is how I see this: 
say I have a base metal dissolved in solution (lets say HCl), and now I add sodium hydroxide, at a certain point the solution looses its acid and the base metal will begin to precipitate, the very reactive sodium (metal) from the sodium hydroxide solution will join with the chloride from our acid (or dissolved base metal) and make table salt (NaCL) this salt is fairly soluble in solution, now the OH (hydroxide) will join with free hydrogen and form some water, and OH will also help to make oxides or hydroxide of our base metals the precipitant in the bottom of our bucket, now if I add a large amount of hydroxide (large excess NaOH) then I can form complexes that again will make our base metal soluble, (gold and silver included can form soluble hydroxides if conditions are right). Now do you use a pH meter?

I do not think you need to worry about a healthy stock pot, and the gold being soluble, and you have your stannous chloride if needed.


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## Geo (Nov 25, 2011)

i use test strips from pool supply.


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## butcher (Nov 25, 2011)

My pool supply also has pH indicator solutions, these will work where the solutions are not colored strongly by metals.

I was curious about the chlorine tests strips they sell have you tried them?


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## Geo (Nov 25, 2011)

no. i just have strips to test PH.


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## g_axelsson (Oct 10, 2013)

This is an old thread but I wanted to add one possibility to why it looks like lye is dissolving gold.



Silver Handle said:


> Funny you should ask. the lye did lighten the color somewhat.


A couple of years ago I did try to remove solder mask from fully plated boards (old HP boards) but after a while in lye some of the gold fingers turned white. The gold wasn't dissolved, it was a white metal that had plated on top of the gold.

My theory (I haven't tested it yet) is that led is dissolving in strong lye. Then the weak solution with lead plates out on another surface which is in contact with a less noble metal, tin for example. So when tin is oxidized the lead plates out on top of the gold.

If lye would dissolve the base metal under the thin gold we should expose pure copper, not a lighter color track.

My cards were cut down in small pieces so not all fingers had contact with solder and only a couple of the fingers got plated. The later AP process removed the copper and left the gold as usual.

As a footnote I think Silver Handle got a bad advice, as I read the thread he had used AP and got the advice to drop the gold from the AP with SMB. He probably had the gold as a fine sediment in the bottom already and it wasn't dissolved. Adding SMB to that probably just created a mess. The one giving the advice probably thought he had already dissolved the gold.
I hope he got his gold in the end.

Göran


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