# base metal in finger



## ericrm (Feb 10, 2012)

i already know that in pins, most of the time gold is plated over nickel and nickel is plated over copper or brass but is it the same thing for finger ?
i often end up with finger that have copper left on them but with the gold foil remove,with made me think that maybe it is the same plated patern than pins.does anyone have clues about that?
i have scratch with a knife and it apears to be gold over copper but maybe im just missing it since it is a very thin layer.


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## Geo (Feb 10, 2012)

the base metal is in the same order. copper/nickle/gold. the nickle is used as a barrier to keep the gold from migrating to the copper.


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## ericrm (Feb 10, 2012)

a lightening fast answer :lol: realy apreciated
and if i understand you correctly every gold plated item (in electric) will be over nickel ,to avoid over the year to have the contact turn bad because of copper oxide
thank you geo


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## Geo (Feb 10, 2012)

actually the barrier is to keep the gold from migrating (or mixing) with the copper. karat gold can be gold and copper because the two have an affinity to one another (they are attracted to one another). if you try to plate gold directly on to copper, the gold will eventually be absorbed into the copper. the nickle has a different polarity (or something like that) so it doesnt mix as readily with copper or gold and thats why its used as a barrier between gold and copper.


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## ericrm (Feb 10, 2012)

ok
thank you for the clarification


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## Anonymous (Mar 2, 2012)

Geo said:


> actually the barrier is to keep the gold from migrating (or mixing) with the copper. karat gold can be gold and copper because the two have an affinity to one another (they are attracted to one another). if you try to plate gold directly on to copper, the gold will eventually be absorbed into the copper. the nickle has a different polarity (or something like that) so it doesnt mix as readily with copper or gold and thats why its used as a barrier between gold and copper.


Thanks for the information. Knowledge Is Power. I learned something new today which will be hard for me to forget.


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## ericrm (Nov 26, 2012)

does anyone know the ratio of base metal over the complete finger?

i have weighted some leached finger vs some unleached one but since i havent tough of it before ive just used similar finger to compare weight...
with this ball park i have come to 13% of gold and base metal by weight... anyone can confirm or unconfirm ?


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## jmdlcar (Nov 27, 2012)

You have weigh them before you process them and then weigh them after process that might gave a better number.


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## etack (Nov 27, 2012)

Eric instead of weighing them use surface area calculations. Sam's web side is really good for it. I would make the plating thickness for those fingers in you pic to be about 30 micro inches it might be more, but shouldn't be less. I believe that it takes 105.396 sq inches to make a gram. One sq/in has a value (Au $1747.00 USD) of $0.53USD.
http://goldnscrap.com/index.php?option=com_content&view=article&id=72:gold-plating-calculator&catid=49:calculators&Itemid=66

Eric


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## Rodger Hamilton (Dec 7, 2012)

I suspect you really want to discover the value of gold on each finger.

Forget about weighing a single finger, that will only lead to confusion... First, discover the amount of gold plate the finger.
The average AGP finger has about 0.006 grams of gold... in today's money is about $0.33US (33 cents).

Then you do a "head count" and a bit of math to figure with good accuracy the value of the lot.


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## ericrm (Dec 7, 2012)

lol thank for the answer my concern was not about gold, i wanted to know what was the minimum nitric acid i could use to remove the base metal by weight :lol: ... and since im not a very educate man ive just drop the gallon in the bucket and add finger until it stop working 8) ... than add a little more acid to finish... but since i add too much ,ive add a new batch of finger than a little acid than finger than..... should have stayed in scool :lol:


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## Rodger Hamilton (Dec 8, 2012)

Sorry I misunderstood your post.

Indeed what you ended up doing is the prudent thing to do to use as little acid as possible considering the cost of nitric and the unknown mass of the copper.

And if you read around the forum you may discover that dissolving gold in AR is a similar procedure with benefits beyond saving the nitric.


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## goldsilverpro (Dec 8, 2012)

The copper on a board is usually 1 oz (an av.oz. in this case = 28.4g) per square foot or 2 oz per square foot, if I remember right. Assuming the gold on the fingers is 30 microinches thick, that would make the copper 133 to 266 times thicker than the gold, if my math is right. That's why some rookies peel the foil off of fingers and conclude that the gold is very thick.


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