# Surface Area Calculation



## goldsilverpro (Jul 31, 2007)

To estimate the value of the gold plating, you must first measure and calculate the surface area(s) that it covers. This requires working with the formulas of geometric shapes.

This link gives the formulas. If you click on "online area calculator", or use the second link below, it brings up a page where you select the specific shape (triangle, circle, etc.) that you are working with. When you do this, a small window will prompt you for data (radius, height, etc.). When these are entered, it will calculate the area.

http://math.about.com/library/blmeasurement.htm

http://math.about.com/library/weekly/aa062502a.htm


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## lmills148 (Aug 22, 2007)

thanks for starting a new thread on this


goldsilverpro said:


> To estimate the value of the gold plating, you must first measure and calculate the surface area(s) that it covers. This requires working with the formulas of geometric shapes.


GSP
Do you know the weight of gold per cubic MM. The volume is easy enough if you could school me in calculating weight from volume that would help.

Lloyd
EDIT
I didn't realize the scope of the question I was asking. I guess archemedes asked this once too. Here is a link that gives the density of some other metals as well

*http://www.24carat.co.uk/densityofgoldandothermetalsframe.html*


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## lazersteve (Aug 22, 2007)

Lloyd,

The density of gold is 19.3 g / cc

1 cc = (10 mm x 10 mm x 10 mm) = 1000 cubic mm 

so :

the weight of 1 cubic mm or gold must be:

19.3 / 1000 = 0.0193 grams per cubic mm.

Checking we have 

0.0193 x 1000 = 19.3 grams 

Steve


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## Higashi (Aug 14, 2010)

I have a better way, using :

1. camera/scanner
2. ruler/measure tape
3. Adobe Illusrator or any vectorisation software
4. Google Sketchup 6 and above.

Record a picture of your specimen by camera or better more using scanner

measure the distance between two recognizable point in your specimen.

vectorize your image using Illustrator, auto-tracing takes some skill and arts.

Scale your vector drawing using the distance measured in Step B as referrence, the accuracy of this procedure is dependant on this number.

Clean up your vector drawings, neat it up, remove unwanted shapes and lines etc.

import the vector into Sketchup.

Scale it back again in sketchup.

Just open the Entity info in sketchup, it shows the surface area or volume when you click on an item (depends wether you select 2D or 3D entity).


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## samuel-a (Mar 20, 2011)

Those are informative links Chris. Thanks!

Though i gotta say that, in my opinion the most elusive piece of information at most cases are the plating thickness...

While ego i formulated the calculation of how much gold is in gold plating with your help, into a spread sheet and used it to do some "yields guessing" games with myself for plated items.
Since then I've uploaded it to my website for my visitors and the forum members to 'play' freely with this easy and accurate calculator (that is based on perfect conditions). The calculation results are given on the metric system (grams) after being converted from the user input data that is in Inches and troy ounce to allow easier interface to the US user.

- Gold plating Calculator

The calculator does get the job done, it is up to us to enter the right input.

- Other Calculators

Thanks,
Sam


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## joem (Mar 20, 2011)

samuel-a said:


> Those are informative links Chris. Thanks!
> 
> Though i gotta say that, in my opinion the most elusive piece of information at most cases are the plating thickness...
> 
> ...


does not seem to work, or is it me?
what is the average area of a plated jumper pin and what is the average plating in micro inches?
Maybe I need your better estimates


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## samuel-a (Mar 20, 2011)

joem said:


> does not seem to work, or is it me?



It's not you, right after i wrote this post i've done some design editing to the page and i think the editor screwed the code, the calculator's is now not aligning with my own spread sheet calculator. I'll get right on it and update when fixed. Thanks again to GSP for pointing that out to me

EDIT: Problem fixed. Thank you for your feedback guys.


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## joem (Mar 20, 2011)

ok by using the search button ( yes I use it) I found this 



> Dollar value of gold plating = Spot price divided by 100,000 X thickness in micro" X area in square inches.
> 
> Example: The gold spot is $650. You have 9.58 square inches of gold plate that you estimate to be 30 micro" thick.
> 650 divided by 100,000 X 9.58 X 30 = $1.87.



So I did a quick math and used very conservative numbers.
Anyone can feel free to correct me.

I did an estimate on a pin I clipped
$1427 / 100,000 x .1 x 15 = $0.00021405 / pin
I measured 2 grams of 130 pins so it's worth $0.027885
My little bag has 47 grams to it may be worth a total of $0.6552975


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## Militoy (Apr 7, 2011)

OK – I didn’t run through all the calcs to check out the “rule of thumb” estimate on values – and I’m not sure I understand the dimensions of your pins - but running through your figures, I think you might be seriously cheating yourself. Your pins seem to work out to about 0.0318 dia, 1 inch long (or equiv area), for the 0.10 square inch estimate. At 15 microinches plating thickness, you should have 1.5 x 10 -6 cubic inches of gold plating per pin, or 25.58 x 10 -6 cubic centimeters – or 474 x 10 -6 grams. At today’s spot price of gold ($1454.70 as I write this), that’s $.03576 per pin. So if 2 grams of pins are 130 pins, 47 grams are around 3055 pins. At $.03576 per pin, that’s about $109 – not 65 cents - assuming pure gold. Of course - you need to allow for recovery losses and alloy content, etc...


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## joem (Apr 7, 2011)

Militoy said:


> OK – I didn’t run through all the calcs to check out the “rule of thumb” estimate on values – and I’m not sure I understand the dimensions of your pins - but running through your figures, I think you might be seriously cheating yourself. Your pins seem to work out to about 0.0318 dia, 1 inch long (or equiv area), for the 0.10 square inch estimate. At 15 microinches plating thickness, you should have 1.5 x 10 -6 cubic inches of gold plating per pin, or 25.58 x 10 -6 cubic centimeters – or 474 x 10 -6 grams. At today’s spot price of gold ($1454.70 as I write this), that’s $.03576 per pin. So if 2 grams of pins are 130 pins, 47 grams are around 3055 pins. At $.03576 per pin, that’s about $109 – not 65 cents - assuming pure gold. Of course - you need to allow for recovery losses and alloy content, etc...



I took the lowest plating (10k gold) and the pins are about 3 mm long not 1 inch long. I also considered suface area not the thickness(which is not solid gold)


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## goldsilverpro (Apr 7, 2011)

joem said:


> ok by using the search button ( yes I use it) I found this
> 
> 
> 
> ...



1427/100000 x .1 x 15 = $.021405/pin
.021405 x 65 x 47 = $65.39/47 grams

There is no such thing as 10K plated gold on electronic materials. For pins, etc., it will usually be very close to 24K. Usually about 99+% pure. They add about 0.1% to 1% of Co or Ni to harden it.


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## joem (Apr 7, 2011)

Thanks GSP
I thought they were plated as fingers and decimal placement makes a huge difference. I guess I need to start clipping pins or is the volume of boards (about 600 lbs) I have worth my time? The only pins I processed were in A/P and it took many weeks to see results. hmmmmm

but question? where does the 65 come from in your equation?


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## samuel-a (Apr 7, 2011)

Joam

If i understand correctly, you based your calc' on: 
0.1 sq. inch of surface area per pin
15 micro inch of thickness
1427$ spot price

That turns out in my calculation as: 0.021765 $ per pin.
therefore: 47 gram * 65 pins per gram * 0.021765 = 66.49$

That figure is kinda high to my opinion no matter which calculation used, i think you should measure your pins again.
Thickness is only an educated guess and can be anywhere from 10-30 micro inches.


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## trashmaster (Apr 7, 2011)

I need to buy a new calulator (mine just broke) when it told me that I took 120-140 lbs. of pins to barren realms 007 that is worth OVER $85,000. :lol: :lol: :lol: (I Know The Numbers Are Not Correct) :evil: :twisted: but barren and I would never have to work again.


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## joem (Apr 7, 2011)

Now I'm just not sure anymore. No Joke. Can someone do the math on a clipped jumper pin and let me know if I should just sell my boards as is or should I start clipping more pins?


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## Barren Realms 007 (Apr 7, 2011)

trashmaster said:


> I need to buy a new calulator (mine just broke) when it told me that I took 120-140 lbs. of pins to barren realms 007 that is worth OVER $85,000. :lol: :lol: :lol: (I Know The Numbers Are Not Correct) :evil: :twisted: but barren and I would never have to work again.



I didn't even think about that in relation to those pin's. If they were worth that much I would have processed them already rather than working on building my ball mill this week. :mrgreen:


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## goldsilverpro (Apr 8, 2011)

joem said:


> Thanks GSP
> I thought they were plated as fingers and decimal placement makes a huge difference. I guess I need to start clipping pins or is the volume of boards (about 600 lbs) I have worth my time? The only pins I processed were in A/P and it took many weeks to see results. hmmmmm
> 
> but question? where does the 65 come from in your equation?



130/2 = 65 = # of pins per gram. Those are very small pins and the surface area/pound would be quite high.


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## Barren Realms 007 (Apr 8, 2011)

goldsilverpro said:


> joem said:
> 
> 
> > Thanks GSP
> ...



That dosen't mean the plating will be very thick. I ran some very small pins and the yield was low on them because they were thinly plated. But I do agree with you.


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