Yellow gold and pink gold

[goldmich]

Hi everybody.
I am new here, and besides Frenchie, so i beg your pardon about my language mistakes, and above all for my ignorance about refining .
I am here for learning.
I meet a problem.
I have dissolved a very small quantity of gold (1g of 750/1000) in aqua regia.
After dissolving, at the bottom I saw there was small black particles unsoluble, i think it was silver chloride (?).
I filtered the solution then i added about 100ml of demineralized water.
Then i tried to electro-plate some small things, with graphit electrode and under 5 to 7 volts.
The result is really horrible.
The problem is that i try to renovate some pieces of my guitar, gold plated from factory, but worn by the use (the hand on the tailpiece).
And the original gold is very deep yellow, almost turning to clear orange.
But my plated gold is really different, clear and not yellow at all. I thought it was the thickness, but after more than one hour of plating the color stays the same.
However the dissolved gold, ( i mean the solid gold, before dissolution) was very near of the guitar's color, if not identical.
I can't understand what happened, and I hope that some scientists in that forum will help me to understand and to correct my actions.
Thanks for reading.
Goldmich

 

[Pantherlikher]

Hi...
Before you can jam in a rock band, you need to first learn to finger right?...
Read the introductions and safety sections here before you even think about trying anything. You will hurt yourself if you do not.

Please learn to play before thinking you're a rock star.

B.S.

 

[FrugalRefiner]

Goldmich,

Welcome to the forum. I'm afraid gold plating is much more complicated than just dissolving some gold in aqua regia. Plating baths are finely balanced, complex solutions, and the companies that make them guard the formulas carefully. If your goal is to replate a few pieces, you'll have better luck buying some commercial plating solution. Even then, you're not likely to get as good results as a plating company. For the best results, you'll need to take the parts to a plating shop and have them do the job.

Dave

 

[goldmich]

Hello
Thanks for your answers.
To pantherlikher:
Don't worry,I used a lot of protections before beginning my tests, and I have read a lot of articles concerning the different dangers when doing such things.
So don't be afraid for my health, i am rather careful.
To reassure you, i would say that I am near to reach the 70 years.(and about my finger play, I play guitar since my 13 years, so I begin to know the guitar handle)

To frugalrefiner:
Yes i agree, a profesional would surely do better than me, but i hoped some advices rather than discouraging words, because what could be the hobbies
if we call a professional every time we need something ? (even for the fun)
I use to do all by myself, the complete list would be too long, i prefer to only speak about two things that i never did.
1) I didn't do the Universe.
2) I didn't do myself.
o))
But seriously, I spent all my life by learning new things and about gold plating I don't have the intention to give up.

But It is time for me to learn that kind of things, I wish someone will try to answer to my questions ,
or at least to try to help me, because i searched all the Net and didn't find.
Concerning the use of Aqua regia, i give you one (amongst thousand) address on the Net, talking about gold plating directly with aqua regia.
I know it is a very small and simple example, but it shows anyhow that it is possible to plate gold by immersion and with rather good results.
Besides of the interest for me to learn such things, the price is also a reason for me to attempt to do it by myself.
Anyway, If nobody can help me here, too bad, I will keep searching until I find a response to my questions.
Thanks for your welcome and your answer.

Goldmich.

Here the address of the "gold plating for the fun" (not written by a kid, the guy is a chemist)
http://wiki.scienceamusante.net/index.php?title=Dorure_d'une_cl%C3%A9_par_%C3%A9lectrolyse

 

[goldsilverpro]

Convert the aqua regia solution to a ferricyanide system (actually, should be ferrocyanide), as in the link you gave, and you may (or, may not) have better luck.

I would totally agree with FrugalRefiner's post above. If you want to learn how to plate, go to the professional literature and learn from people that are actually real platers. Stay away from anything written by people that are not in the plating industry, even if they are Nobel prize winners. The advice given in that link is pretty amateurish, to say the least.

 

[goldmich]

Stay away from anything written by people that are not in the plating industry, even if they are Nobel prize winners. The advice given in that link is pretty amateurish, to say the least.

Thanks
I think I will follow a best way, as you say (and as said frugalrefiner), because all my tries with the aqua regia are rather strange.
Discouraged by this electro plating of dream ... it seems to be a kind of joke (given the results), because I successively obtain
almost all the rainbow colors with my solution EXCEPTING precisely the pure yellow that I need.
I will now recover the metal from the aqua regia before loosing all for nothing.

I think you are very nice and patient, and I will add that i also spend long time by saying the same things than you on my usual forum
(electronic creation and repair) forum where a lot of beginners are coming, hoping to build fantastic circuits without a crumb of
knowledge, because they read on the Net that "It's so easy".They even don't know how to make a tin solder but they hope to built a argon laser...
And (you will smile) I also use the phrase: "Stay away from people showing a schematic riddled with errors and who tell that it works fine,
your main and bigger risk is only to buy a ton of expensive components for nothing"
And it is precisely your identical sentence that decided me to give up momentarily and to learn more before trying again by other ways.

Thanks for all.(and to all)
Have a good day.

 

[goldsilverpro]

Here's a link with information on the ferrocyanide system. Check the posts by Goran Budija.

http://www.finishing.com/233/01.shtml#new

 

[goldmich]

Hello Goldsilverpro
Now that i am near to give up you give me new adresses that give me a envie to try again with the method you are talking about.Thanks a lot anyway.
I have a question more.
When i dissolved my gold (750/1000) in the aqua regia, then filtered to eleminate some black particles on the bottom, then melting anew after precipitation,
can i think now that i get 0.6 g of pure gold (pure meaning about 980/1000) ?(0.6 because i lost a small part in my different tries of plating)
I am really grateful for you help.

I have read some things about cyanide ..and even if i am 70, i yet not decided to die , because the small texts that i have read on such system are rather frightening.
But i suppose that the usual precautions are sufficient, gloves, glasses, special clothes, extractive air hood etc...
If i dare to throw myself in that way, i promise i will come back to tell you what, how, where, and the results.
I noticed that when i help something (in electronical things )the only one reward that i wish is to see the guy coming back to say what he did and talking
about his success (or defeat)
Elementary politeness i think.
Have a good day.
goldmich

 

[goldsilverpro]

Although ferrocyanide is toxic, it is much less so than cyanide. It takes about 350 times more potassium ferrocyanide to kill you by ingestion than it does potassium cyanide.

If you had started with pure gold, you may have had more success. I don't agree with the article that just any gold object will work. Any gold less than pure is contaminated with other metals. Success will depend on which metals are involved and in what quantities. However, if the gold you used was 18K yellow or pink jewelry gold, the main contaminant in the aqua regia would now be copper, which would be less of a problem than about any other metal I can think of.

Assuming the copper is no problem, I would next look at the aqua regia you used. How much hydrochloric acid and how much nitric acid did you use and what was the total volume? If you used too much nitric or if you used too much total volume, that could have caused big problems with the plating deposit. To dissolve 1g of karat gold, it will take a little less than 5ml of aqua regia or, a little less than both 1 ml of 70% nitric acid and 4ml of 37% hydrochloric acid. What did you use?

Lastly, what did you use for a power supply? The guy says to use between 4.5 and 6.0 volts. Did you do that? Too little or too much could cause problems, especially too much.

In other words, if you didn't follow the man's instructions EXACTLY, I can see how you could of had problems.

 

[goldmich]

Yes, i did exactly like he said, and even more carefully, i used the less possible of aqua regia, (1nitric-4 chlorohydric), by beginning by putting the gold
solely in the chlorohydric acid (4ml) then adding the nitric acid drop after drop (while heating) and waiting the end of the reaction before adding a
new nitric acid's drop.(I have read that acting this way the quantity of nitric is limited at its necessary minimum to produce the chlore).
When the gold was finally dissolved, the color of the solution was dark yellow, looking like a liquor.At the bottom some little black particles was visible.
But anyway, the problem seemed to be elsewhere.
Because after the gold dissolution's end, (and after filtering) the solution was extremely acid, (even after dissolution in 100 ml of deionised water)
so when i began to apply a current, it was absolutely impossible to work with 6 or 7 volts, because at such a voltage the current was reaching 2A and
the plated piece was immediately turning dark.
To stay under 10 or 15 mA i was obligated to plate with 2.5 volts! (but anyway this is better than too much voltage, because the plating time is not important for me)
But after each try, the plated layer was moving between very clear yellow and rose or clear red, sometimes looking like a copper plating, sometimes like clear brass.

Anyway:
I have read all about the topics you indicate (very interesting), and i found out that the main problem was to buy Potassium Ferrocyanure in France,
the sell is very limited and strictly regulated.
Besides the only one supplier that I found (not sure that he would sell to a simple citizen) talks of big quantities (1 kg) while I need 15 grams.
I asked if he can send 250 grams (price : 80$ !) and I am waiting for his answer, but... at such a price i can also buy 100ml of 24K gold solution made
by a professional (thus perfect), and so avoid all these problems.100 ml would be enough for all my guitar parts.

I think i will do that way, because this "temporary hobby" was only motivated by my guitar...and between the woodwork, carpentry, masonry, roof refection,
electronic gadgets, electrical wires for garden ilumination and a lot of other things, i have enough to occupy all my time until the end of my life.

I want to thank you once again very much for your help.
Have a good day.
goldmich

 

[FrugalRefiner]

While my first post may have been discouraging to you, I prefer to be honest with new members. Our forum isn't really about plating, it's about refining the precious metals. But thanks to extremely knowledgebale member like GoldSilverPro and others I've learned enough to know that it's one of those processes that isn't done easily or without a great deal of study. GSP is a Pro with over 40 years of experience in both refining and plating and I value the wisdom he has shared with us.

It's not that you can't gold plate something yourself. I did it as a kid with one of the many chemistry sets I received at Christmas. But it's more about the quality of the plating. My little gold plating wand was able to put a nice yellow color on shiny metal. But if you rubbed on it just a little bit, the gold color disappeared.

A plating shop is set up to prep, clean, strike, and plate your items with a layer of gold that will last through more than a few cleanings of your instrument.

Unless refining and plating is a passion for you, hire someone to do a professional job and spend your time honing your own skills on the guitar.

Dave

 

[goldmich]

Unless refining and plating is a passion for you, hire someone to do a professional job and spend your time honing your own skills on the guitar. Dave

Yes, thank you very much frugalrefiner, this is exactly what i lengthily developed in the end of my last message.
I previously had understood by myself, no need to bury the corpse deeper again...I will now leave this forum.

Thanks again to goldsilverpro who really knows what he talks about.

Good bye

 

[goldmich]

Hello all .
I hope that goldsilverpro will look at my new question.
I noticed something. If i put my the piece that i want to plate in the solution, (without current, only the piece ), after several minutes it turn brown, then goes to black.
I precise that I perfectly cleaned the piece in aceton, then in electrical way with a cleaning solution and use of inversed polarity)
My question:
Don' t you think that the guy who gives the trick on the French site has forgot to say that the chloroauric solution must be evaporated until total drying before adding deionised water ?
I imagine that maybe such a strong acidity (by keeping all the aqua regia) is attacking the metal in the same time that gold is plated, this would explain why my results are so bad,
if each actions produces a contrary effect of the other.
I imagined a kind of dissolution of the copper (or brass) of the piece in the same time that the electrical current tries to transfer the gold.
Anyway, now i recuperated all my gold by precipitation, then hydrochloric, rinsing, then ammonia and several rinsing in deionised water, and finally by melting in a crucible.
(it is really beautiful yellow now, maybe my actions have refined a bit ?)

Well, can you tell me please what you think about my idea of totally evaporate the solution before deionised water addition ?
I thought that it should (perhaps) be better to work with a neutral solution in which only the dissolved gold would be electrically conductor.
Thanks for reading.
goldmich.

PS
I already ordered 100 ml of professional cyanide solution and some tools usefull for plating of sure way, and my question is only a curiosity question.