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Re: Metal Density Testing Method
Posted: Wed Dec 07, 2016 6:07 pm
by DirtScanner
Make sure they are to 2 decimal places Dave and the lower the range the more accurate they will be unless you spend lots on them
Re: Metal Density Testing Method
Posted: Mon Apr 03, 2017 8:54 am
by chesters4
Very interesting post.
In one field i found a marked earing 875 and presumably an asian gold ring .
The earing came well down in foil as would be expected but strangely the ring came in as zinc! (Both on its side and on its edge)
Using the method in the post the ring weighed 9.1 gm and displaced 0.5gm so although your scale doesnt go above 22c its just above it so i guess just over 22c?
Cannot think of anything else it can be in the same field was a tungstan ring which was mighty heavy but not gold coloured
It does though mean a better set of scales is needed before i am absolutely certain
Does the method work if the ring has stones in it?
Re: Metal Density Testing Method
Posted: Wed Aug 09, 2017 3:36 pm
by Koala
I have tried this a few times. Results are very hit and miss.
Solid gold ring bands work fine as long as you use scales with two decimal places. Three would be better.
However most of what we find is an unknown alloy. Also bubbles in the casting process alter the results greatly. I checked the results with an Irregular iron hinge thing. Results came back as aluminium due the internal bubbles.
Smooth objects should be fine. Might retest on some known coins and try and calibrate the setup as Water volume alters greatly with temperature and also affects the results.
Smaller the volume the better
Re: Metal Density Testing Method
Posted: Wed Aug 09, 2017 4:55 pm
by Fusion
As stated in my earlier post:
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.
Re: Metal Density Testing Method
Posted: Sun Dec 03, 2017 11:17 pm
by Trotboy
I don't see how this can be correct. Density is calculated by Mass (The weight of the object on your scales) divided by Volume (Which would be the millilitres of water displaced by the object. How can the scale measure volume? It can't, it can only give you a measurement of the mass.
Re: Metal Density Testing Method
Posted: Sun Dec 03, 2017 11:30 pm
by Twit
Trotboy wrote: Sun Dec 03, 2017 11:17 pm
I don't see how this can be correct. Density is calculated by Mass (The weight of the object on your scales) divided by Volume (Which would be the millilitres of water displaced by the object. How can the scale measure volume? It can't, it can only give you a measurement of the mass.
The object increases the volume of water weighed - it is as if the object was a volume of extra water, which via the weight of it measured, returns a density figure in the calculation.
Re: Metal Density Testing Method
Posted: Mon Dec 04, 2017 3:04 am
by Koala
I have tried it.
Works fine for smooth things like a gold ring.
Irregular objects catch too many air bubbles.
Anything porous forget it.
Most alloys forget it as you don't know what percentage of each element.
Small items, small errors equal big differences. A small lead object that was both porous and irregular came back as aluminium.
Nice to add another diagnostic tool but recognise it limitations.
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 4:35 pm
by Dave8472
Thread pictures fixed on first post
Dave
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 4:53 pm
by fred
MetalGuru wrote: Fri Apr 26, 2013 10:50 pm
The boss wrote: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
Absolutly correct. The scientist was Archimedes, who jumped out of his bath shouting eureka, which means, 'I've found it'.
All this makes my brain hurt. I'll probably just settle for having the bath.
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 5:10 pm
by Phil2401
fred wrote: Sun Mar 18, 2018 4:53 pm
MetalGuru wrote: Fri Apr 26, 2013 10:50 pm
The boss wrote: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
Absolutly correct. The scientist was Archimedes, who jumped out of his bath shouting eureka, which means, 'I've found it'.
All this makes my brain hurt. I'll probably just settle for having the bath.
Just out of interest (Fred you may know the answer to this) - how much does it cost to have your friendly local jeweller do an acid scratch test and give you an accurate assessment?
Phil
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 5:17 pm
by fred
Phil2401 wrote: Sun Mar 18, 2018 5:10 pm
fred wrote: Sun Mar 18, 2018 4:53 pm
MetalGuru wrote: Fri Apr 26, 2013 10:50 pm
Absolutly correct. The scientist was Archimedes, who jumped out of his bath shouting eureka, which means, 'I've found it'.
All this makes my brain hurt. I'll probably just settle for having the bath.
quote]
Just out of interest (Fred you may know the answer to this) - how much does it cost to have your friendly local jeweller do an acid scratch test and give you an accurate assessment?
Phil
Nothing if he thinks that you are thinking of selling it to him!
Be wary though because many high street jewellers are little more than salesmen and have no knowledge of precious metals beyond reading hallmarks.
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 5:31 pm
by Phil2401
Thought that might be the reply
Below is a hardly scientific, but plausible account of the use of the Acrhimedes principle as a basis for measuring density -
http://www.longlongtimeago.com/once-upo ... den-crown/
Phil
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 6:02 pm
by Rhumours
wait .... na na na na na ..... this is a lie ..... or witchcraft. .... or both ...... but it can't possibly work. You have displaced nothing. And it wasn't to measure density it was to measure the volume of a uneven object like .... a branch of a tree or a spiky ball something odd shaped. Bring the water to the top of the container ... whatever spilled over was displaced which meant that the lost volume of water was exactly the dimensions of the inserted object. No jokes
This can't work surely
.... you may have increased the density of the water very marginally which may be what is being registered
And asking a jeweller to in essence value something usually carries a charge. If you want a piece of paper saying what it is that's a valuation for insurance purposes and usually costs 10% of the value of the item valued. "I would like this sized but not sure what metal it is could you check it is gold for me before I commit" is disgusting behaviour and I wouldn't offer that as a solution.
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 6:12 pm
by Phil2401
Rhumours wrote: Sun Mar 18, 2018 6:02 pm
wait .... na na na na na ..... this is a lie ..... or witchcraft. .... or both ...... but it can't possibly work. You have displaced nothing. And it wasn't to measure density it was to measure the volume of a uneven object like .... a branch of a tree or a spiky ball something odd shaped. Bring the water to the top of the container ... whatever spilled over was displaced which meant that the lost volume of water was exactly the dimensions of the inserted object. No jokes
This can't work surely
.... you may have increased the density of the water very marginally which may be what is being registered
And asking a jeweller to in essence value something usually carries a charge. If you want a piece of paper saying what it is that's a valuation for insurance purposes and usually costs 10% of the value of the item valued. "I would like this sized but not sure what metal it is could you check it is gold for me before I commit" is disgusting behaviour and I wouldn't offer that as a solution.
Rhumours - if you actually read the post, nobody is asking a jeweller to 'value' the item, but merely to establish its precious metal content.
If also you were to read thought my previous post, you would understand better the correlation between weight / displacement / density etc....the ancient theories are not dissimilar to contemporary opinions.
Phil
Re: Metal Density Testing Method
Posted: Sun Mar 18, 2018 6:20 pm
by Rhumours
Phil2401 wrote: Sun Mar 18, 2018 6:12 pm
Rhumours wrote: Sun Mar 18, 2018 6:02 pm
wait .... na na na na na ..... this is a lie ..... or witchcraft. .... or both ...... but it can't possibly work. You have displaced nothing. And it wasn't to measure density it was to measure the volume of a uneven object like .... a branch of a tree or a spiky ball something odd shaped. Bring the water to the top of the container ... whatever spilled over was displaced which meant that the lost volume of water was exactly the dimensions of the inserted object. No jokes
This can't work surely
.... you may have increased the density of the water very marginally which may be what is being registered
And asking a jeweller to in essence value something usually carries a charge. If you want a piece of paper saying what it is that's a valuation for insurance purposes and usually costs 10% of the value of the item valued. "I would like this sized but not sure what metal it is could you check it is gold for me before I commit" is disgusting behaviour and I wouldn't offer that as a solution.
Rhumours - if you actually read the post, nobody is asking a jeweller to 'value' the item, but merely to establish its precious metal content.
If also you were to read thought my previous post, you would understand better the correlation between weight / displacement / density etc....the ancient theories are not dissimilar to contemporary opinions.
Phil
Phil
If you actually read my post as intended this would make sense to you
https://www.google.co.uk/search?q=irony ... e&ie=UTF-8
I understand the principle just fine dude .... I did physics at school