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Old 08-07-2017, 03:31 AM
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ToddB64 ToddB64 is offline
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Default Testing Density of Jewelry to Determine Value

Hi !

If interested in testing the density of your jewelry to determine it's value, read on.....

The (4) pictures attached show my handmade test stands made of wood and painted white.

In this instance we are only concerned with the water bowl/digital scale test method based on the Archimedes principle. (The Graduated cylinder is another method of determining density, but not addressed in this post.)

#1 First, the digital scale is turned ON and the item is weighed dry and the weight recorded.

#2 Then a clear-plastic bowl of distilled water is set on the scale and the Tare button pressed to subtract both the weight of the bowl plus the water .... the scale then reads 0.00. The item in this instance, a 92.5 % Sterling Silver ladies' ring (found metal detecting a soccer field), is hanging by a length of 4 lb. monofilament fishing line, with the upper end wound around a 1" dia. hardwood dowel resting on supports.

#3 The dowel is rotated to lower the ring into the bowl of water until fully submerged, but the ring cannot be touching the sides or bottom of the bowl.

#4 Wait for the ring to settle and stop moving in the water.

#5 The digital scale is weighing just the amount of water displaced by the ring. Record the weight of the displaced water.

#6 Divide the dry weight of the ring (larger number) by the weight of the displaced water (smaller number) and the quotient is the density of the ring. Eureka !

#7 Compare the quotient to the Density column in a Periodic Table to find out what metal the ring is made of, allowing for the fact that density tables are based on pure elements, be they solids, liquids or gases, and the metal of the ring is not pure, so some interpolation of the density number chosen from the table will be neccessary when making a final decision of the metal.

Hope this helps someone !

Toddb64
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Old 08-15-2017, 09:17 AM
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Outstanding detailed post that should be very helpful! Thanks Todd! I have a 24k chain here I may give this a try on..the guy at the jewelry/gold buying store said it was 'only 22k'...The other guy at another gold/jewelry store wanted to cut it in pieces and check each link!. Howcome these guys dont know this?

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Old 08-15-2017, 10:13 AM
flyguy784 flyguy784 is offline
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Originally Posted by Mud-puppy View post
Outstanding detailed post that should be very helpful! Thanks Todd! I have a 24k chain here I may give this a try on..the guy at the jewelry/gold buying store said it was 'only 22k'...The other guy at another gold/jewelry store wanted to cut it in pieces and check each link!. Howcome these guys dont know this?
I'm not sure and don't have the equipment to find out. Perhaps the difference in density between the various carat weights and the other "added" metals is so small, testing it this way is inconclusive.
Perhaps one of the jewelry guys will know, and post.

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Old 08-15-2017, 04:51 PM
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Default Testing Density of Jewelry to Determine Value

Originally Posted by Mud-puppy View post
Outstanding detailed post that should be very helpful! Thanks Todd! I have a 24k chain here I may give this a try on..the guy at the jewelry/gold buying store said it was 'only 22k'...The other guy at another gold/jewelry store wanted to cut it in pieces and check each link!. Howcome these guys dont know this?
Hi Mud-puppy !

Regarding your question in the above quote, I will preface my answer by saying, as alluded at step#7 of my subject post, a Density computation using the Archimedes principle water test only renders an approximate density number for the test sample, therefore some interpolation is necessary when comparing to a Periodic Table which has density numbers based on pure elements.

My answer to your question is the guys at "gold/jewelry" stores probably do know about the water test, but use other methods they consider more accurate and of course, everyone has their own trusted preferences.

I like the water test because it is (a) safe to hands and eyes as apposed to acids, (b) is non-destructive to the test sample as apposed to using acids and/or filing grooves and (c) renders a close idea of the primary metal in the test sample to give a "fighting chance" of a fair deal with the buyer and avoid the classic "rip-off" artist.

ToddB64

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