50 Micron Gold Plate?

[billjustbill]

Today, I bought a Benrus stem-wind wristwatch that is stamped "20 Micron" gold and it got me to think back....

About a month ago, I ran across a garage sale and the fellow said in his younger years he sold jewelry. He had full cardboard cases and cases of heavy men's I.D.-style bracelets, adding up to hundreds of pieces....

He said that they were "50 Micron" plate. Any idea how much gold that is compared to gold-filled? Would it be worth taking it all to a recycler?

 

[mts]

You could do a quick "back of envelope" calculation to get a general idea.

Imagine a standard US quarter that is covered in 50 micron gold plate. That means there is 0.005 cm of gold plating on the whole thing. Going back to your old geometry, you can calculate the surface area of the quarter to be approximately 26 square cm. So the total volume of "surface" gold would be around 0.06 cc's. The density of gold is 19.3g per cc. So the total weight of the gold is 1.158g. That assumes pure 24k gold has been used for the gold plating which is probably not the case so you will need to multiply by an appropriate factor.

If the price of gold is currently $47 per gram, you'd have about $55 worth of gold on that quarter. Again, it probably wouldn't be pure gold. Also, the refiner is going to take his chunk. You could get more or less but the numbers above are meant to give you a general idea.

20 micron would of course give you only 40% of what 50 micron would give you so that same quarter might be worth around $22.

The FTC has guidelines for how thin gold can be on jewelry:

classification - microns
"gold flash" (10 kt.) = .175 microns

"gold electroplate" = .175 microns

"gold plate" = .50 microns

"heavy gold plate" = 2.5 microns

So you can see above that even something called "heavy gold plate" at 2.5 microns would only have $2.75 worth of gold on it (for that same quarter). 50 microns is a VERY thick layer of gold from what I can tell. I'd be worried that this guy was not giving you a straight story or was confused and the items were actually .50 microns. In which case they wouldn't be worth much at all.

These calculations could be VERY wrong because I am just starting to study plated gold. Hopefully someone who really knows what they are talking about can enlighten us both and tell me if I'm way off base. True 50 micron gold plating would be worth scrapping in my opinion if you can get a good price on it.

 

[billjustbill]

Thank you for posting this information. I believe your post to be one of the most helpful and intelligent responses I've seen on any of the topics at Treasure net!!

It was very helpful and gave me insight about microns and gold layering on items.

Again, thank you for sharing,

Bill

 

[benign01]

I am afrais you are dreaming. Firstly you cannot convert cm2 to cc ie cm3 Its not possible. secondly there is a very big flaw in your calcs but I'll let you work that one out. 50 microns on a quarter will yield about 50 cents

Sorry!!!

 

[jerseyben]

Without even doing any calculations, I can tell you there is NO WAY a gold plated quarter has $55 worth of gold in it...

 

[mts]

......Firstly you cannot convert cm2 to cc ie cm3 Its not possible. .....

What is the volume of a cylinder that is 24.26mm in diameter and 0.005 cm tall? Calculate that and you will indeed see that you can "convert" cm2 to cc.

You are right. I made a mistake. The surface area of a quarter is not 26 square cm. It is 9.24 square cm (not counting the edge surfaces).

That changes the gold content to be $41.72 at the per gram price above. If I made another mistake in my calculations then please explain it. I don't doubt that I did. That's the whole point of "back of envelope" calculations. They are done in an imprecise way and usually in haste.

 

[mts]

Without even doing any calculations, I can tell you there is NO WAY a gold plated quarter has $55 worth of gold in it...

You do realize that we are talking about a hypothetical quarter plated with 50 microns of gold which is about 285 times thicker than the standard electroplate of .175 microns. 50 microns is VERY heavy plating. 50 microns is about 2mils. And since the quarter is plated on both sides it's like a 4mil sheet of solid gold the size of a quarter. Take 4 pieces of heavy duty aluminum foil (not that thin stuff), stack them on top of each other so that they are 4mil thick, cut out a disc the size of a quarter, and crumble it up into a nugget. That's how much gold we are talking about. It's not hard to imagine that it would be worth $41.

But if we were talking about the standard .175 microns of gold plating you would be right. The gold value would be about 15 cents.

Again, all of this is "back of envelope" stuff. I may be way off and if so I'm happy to admit it. If anyone sees a flaw in what I'm saying please point it out. I'm here to learn just like everyone else.

 

[EARL51]

as a electroplater that plates gold all day. 50 microns is a five minute plate at 3 volts. I doubt you could see the thickness and it strips off easy enough