Metal Density Testing Method

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Barnet
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Metal Density Testing Method

Post by Barnet » Sat Dec 10, 2011 8:48 am

I've been asked to make a repost of a post I made a while back because it gets referred to often but it's hard to find which explains the density testing method for determining metal composition.

So here it is again.

Zero your scales and weigh the object you want to test, make a note of the weight. This ring weighed 3.91 grams.
IMG_2236.jpg
Place a cup of water on a set of digital scales that are accurate to two or more decimal places. I'm using a Scobby Doo cup as it's the lightest one I have that clear so you can see whats going on, but something like a plastic cup from a coffee vending machine is lighter. Heavier glass cups will tip your scales over the . Reset to Zero, on my scales this is the Tare button.
IMG_2238.jpg
Tie the object to piece of cotton of something similar, I’m actually using a bit of string that came off the netting that comes round oranges as it's very light and non absorbent. Suspended the object in the water, just below the surface so as little as possible of the string is added to the equation. Wait for the scales to settle and take the reading. In this case with the ring, it was 0.25 grams.
IMG_2237.jpg
Simple Math

(Weight of the object) divided by (weight of water displaced)

In this case :- 3.91 / 0.25 = 15.64

Metal Density
Gold 19.3
Silver 10.5
Platinum 21.4
Palladium 12.0
Copper 9.0
9ct 10.9 to 12.7
14ct 12.9 to 14.6
18ct Yellow 15.2 to 15.9
18ct White 14.7 to 16.9
22ct 17.7 to 17.8
Sterling Silver 10.2 to 10.3
950 Platinum 20.1

18ct Gold, lovely ! This is a very reliable and easy method, no chemical testing which involes making a small mark/scratch.

Hope this is of use. Happy Hunting.

[:)
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scrap iron chris
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Re: Metal Density Testing Method

Post by scrap iron chris » Sat Dec 10, 2011 9:41 am

Thanks top bit of info :D

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Re: Metal Density Testing Method

Post by Fusion » Sat Dec 10, 2011 9:42 am

Here's the original thread, which also includes a slightly different method:
viewtopic.php?t=12854
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Re: Metal Density Testing Method

Post by Ants » Sat Dec 10, 2011 10:59 am

Must say I think that is a great idea, will try that
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Re: Metal Density Testing Method

Post by Christoph1945 » Sat Dec 17, 2011 7:32 pm

Thanks for posting that, I will give it a try. All I need now is a scale. B-)

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Re: Metal Density Testing Method

Post by rab the ranter » Sat Dec 17, 2011 8:28 pm

Very cool, all I need to find is some flaming gold.
:))

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Re: Metal Density Testing Method

Post by Allectus » Sun Dec 18, 2011 9:46 am

Thanks for sharing that Barnet.....Very interesting & something I'll be using quite often(hopefully)!

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Re: Metal Density Testing Method

Post by Neil&Julie » Sun Dec 18, 2011 11:54 am

How the chuff does that work!! :-/


Thanks, Im going to bookmark this!
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Re: Metal Density Testing Method

Post by The boss » Sun Jan 08, 2012 4:32 pm

That's a amazing test cheers :)
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Re: Metal Density Testing Method

Post by The boss » Sun Jan 08, 2012 4:58 pm

Neil and Julie,if I'm wrong but you can tell me lol but I think it started when an old scientist sat in a bath n wondered why the water rises,he then filled a measuring cylinder n added different object to the same amount of water and then come up with a mass equasion which would of evolved into this density equation lol I think that's right any how lol
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Re: Metal Density Testing Method

Post by Fusion » Sun Jan 08, 2012 5:44 pm

"How does that work!?"

To work out the density of an object, you need to know two things about it: - the mass (Kg, grams, for example) and the volume (cm-cubed, cc, metres-cubed, etc). Then a simple division of mass by volume gives you density.
Example: Take a 10mm x 10mm x 10mm lump of lead. Volume is 1 cm-cubed (1 cc). On the scales, it will weigh 11 grams (typically). So density = 11 divide by 1 = 11 grams per cm-cubed.

Finding the weight of an object is easy, use some scales.

To find the volume - the method here uses bouyancy. When the ring is just submerged, it displaces (pushes out the way) a volume of water exactly equal to the rings' volume. There is less weight on the string , (say 3.7 grams instead of 4 grams)and an equal amount more weight on the scales (say 50.3 grams instead of 50 grams).
The convenient bit is this - water has a density of 1.00. So if the ring displaces 1 cm-cubed of water, it displaces 1 gram of water, which will be indicated on the scales as a 1 gram increase.

So.... as an example, if you have 50 grams of water in your cup, and you suspend the ring in it, you will have a weight of 50.3 grams (say). This means 0.3 cm-cubed of water has been displaced, by 0.3 cm-cubed of gold. And that's your rings' volume, = 0.3 cm cubed.

As scales aren't perfect, the other method I mentioned (in the link to the original post) may be a little more accurate. By weighing the ring with the cup of water in place, you are taking all three measurements at almost the same point in the scales' range, eg. 50 grams, 50.3 grams and 54 grams.
The original method takes the three measurements at 4 grams, 50 grams and 50.3 grams. The scales may behave slightly different at 4 grams to that at 50 grams.

In theory, you could obtain more accuracy by allowing for density changes of the water. Tap water has a slightly different density to that of pure water, and the density of water varies with temperature. However, if you look at how much difference these two factors make, it is really small, not worth bothering with whatsoever.
Last edited by Fusion on Mon Dec 04, 2017 12:38 am, edited 2 times in total.
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Re: Metal Density Testing Method

Post by Christine k » Fri Apr 06, 2012 6:04 pm

thanks for this information I will test it out with my jewellery later and hopefully find an object worth testing.

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Re: Metal Density Testing Method

Post by nugget11 » Thu Apr 12, 2012 1:20 am

Hi,
this is a nugget of info ,we should have a page /cupboard were we can put this into,for library of reference? ::g

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Re: Metal Density Testing Method

Post by pete » Sun Apr 22, 2012 11:36 am

Some clever poople on this forum

well done. ::g
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Re: Metal Density Testing Method

Post by Dave8472 » Mon Apr 23, 2012 8:48 am

nugget11 wrote:Hi,
this is a nugget of info ,we should have a page /cupboard were we can put this into,for library of reference? ::g
Hi, what we have done is in each sub forum anything that is for reference we have made the topic "Sticky" that means it always stays at the top, the topic is referenced with a light bulb symbol rather than a circle, have a look here ::g

http://www.metaldetectingforum.co.uk/vi ... .php?f=120" onclick="window.open(this.href);return false;

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Re: Metal Density Testing Method

Post by silversurfer » Tue May 29, 2012 1:25 am

Eureka!!

Clever and fun.... now need to find some precious metal....

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Re: Metal Density Testing Method

Post by Anubis » Mon Jul 09, 2012 1:11 pm

I have to admit I am completely blown away by this, every time I come on here I learn something new.
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Re: Metal Density Testing Method

Post by lardbelly » Mon Jul 09, 2012 1:16 pm

Anubis wrote:I have to admit I am completely blown away by this, every time I come on here I learn something new.
I'll second that. Brilliant ::g
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Re: Metal Density Testing Method

Post by Danzigman » Mon Jul 09, 2012 1:49 pm

I just like to say Thank you Barnet.. Thank you for a great post.. I have translated it to danish and suppose it is well used here to. I often link to your post.. So what more can I say.. It si a great post ::g
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Re: Metal Density Testing Method

Post by Dave8472 » Mon Jul 09, 2012 5:34 pm

I still can't get my head round the science that it doesn't weigh the same :D

That's probably why I am not a rocket scientist ::g

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Re: Metal Density Testing Method

Post by Dave8472 » Wed Dec 19, 2012 7:45 pm

Finally got round to buying a cheap set of scales to two decimal places off the internet, as I had a suspect bit of Gold found in a house clearance, no hallmarks. Scales arrived today, did a test on a known bit of 9ct, Steve's numbers were bang on, same can't be said for the yellow metal bit I found, it came in well short lol :))

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Re: Metal Density Testing Method

Post by roddas » Wed Dec 19, 2012 10:25 pm

Thats a top bit of info, clever people ::g

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Re: Metal Density Testing Method

Post by kopparberg » Sun Dec 30, 2012 9:09 am

nice one very well done ::g
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Re: Metal Density Testing Method

Post by floyd » Wed Jan 09, 2013 11:28 pm

Ok let me be the first thicko to admit ive not got it.......3.91 divided by 0.25 =15.64......where does 18 carat come into it......der
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Re: Metal Density Testing Method

Post by Danzigman » Wed Jan 09, 2013 11:42 pm

floyd wrote:Ok let me be the first thicko to admit ive not got it.......3.91 divided by 0.25 =15.64......where does 18 carat come into it......der
The density is already known factor.. And if you hit the scale at 15.64 that makes it gold.

Metal Density
Gold 19.3
Silver 10.5
Platinum 21.4
Palladium 12.0
Copper 9.0
9ct 10.9 to 12.7
14ct 12.9 to 14.6
18ct Yellow 15.2 to 15.9
18ct White 14.7 to 16.9
22ct 17.7 to 17.8
Sterling Silver 10.2 to 10.3
950 Platinum 20.1
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Re: Metal Density Testing Method

Post by coinhunteruk » Mon Jan 14, 2013 7:21 pm

Hi there good little test but I got 8.92 ? So what's that ?
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Re: Metal Density Testing Method

Post by Danzigman » Mon Jan 14, 2013 7:24 pm

coinhunteruk wrote:Hi there good little test but I got 8.92 ? So what's that ?
Dont know.. Maybe a brass alloy.. Goldsmith can do an acid test..
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Re: Metal Density Testing Method

Post by former member » Mon Jan 14, 2013 7:29 pm

Most likely a phosphor bronze alloy ::g

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Re: Metal Density Testing Method

Post by coinhunteruk » Tue Jan 15, 2013 8:45 am

thanks for the reply guys been looking on the internet and 8.92 is nickel and nickel silver .
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Re: Metal Density Testing Method

Post by keg83 » Tue Jan 15, 2013 9:33 am

This is very useful to know . My scales have been ordered now, can't wait for them to come so I can test some of my finds . Thanks again :)
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