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[mcmudden]

I would like to verify that any gold bars I happen to buy here are in fact ... made of gold ... and apparently the best way to do this is to get my hands on an ultrasonic thickness gauge (or meter). I've tried to find shops that sell scientific instruments for this purpose, but everyone seems clueless as to what this is, and the answer I seem to always receive is: "we can't get that".

I'm assuming that somewhere in Thailand is a shop that either stocks, or can order, such a device. They're hand-held, about the size of a calculator, and cost USD$400-600. The Omni TM-8812 in particular comes to mind (attached), but there are several other brands and models that should do the trick.

Can anybody shed any light on this? Many thanks for any suggestions!

Omni TM-8812 Ultrasonic Thickness Gauge Spec Sheet.pdf

[kwonitoy]

You'll be able to buy any of these from an NDT (Non Destructive Testing) supply house.

A site like ndtcabin.com will have suppliers.

As an NDT operator for the last 35 years I wouldn't put any faith in a D meter being able to tell me if a material is gold or not

[Naam]

the problem is that a normal thickness gauge cannot differentiate between Gold and Tungsten because there's only a tiny difference in density.

[saakura]

An ultrasonic gauging instrument only determines the thickness, it cannot determine if it is pure gold or an alloy.

[Naam]

An ultrasonic gauging instrument only determines the thickness, it cannot determine if it is pure gold or an alloy.

but it can determine the thickness of two metals if a minimum difference of density exists. fake gold bullion is never an alloy but usually a core of Tungsten (Wolfram) coated by gold. as the difference of Tungsten in weight/density varies only a tiny fraction from gold the discussed gauging instrument is indeed useless.

[mcmudden]

An ultrasonic gauging instrument only determines the thickness, it cannot determine if it is pure gold or an alloy.

but it can determine the thickness of two metals if a minimum difference of density exists. fake gold bullion is never an alloy but usually a core of Tungsten (Wolfram) coated by gold. as the difference of Tungsten in weight/density varies only a tiny fraction from gold the discussed gauging instrument is indeed useless.

Well, if you do a little research, you'll discover that these ultrasound measuring devices measure the speed by which sound waves travel through the material, having nothing to do with density. Sound propagation velocity in tungsten is drastically different than sound propagation velocity in gold, which is exactly the purpose for using the device.

[Naam]

An ultrasonic gauging instrument only determines the thickness, it cannot determine if it is pure gold or an alloy.

but it can determine the thickness of two metals if a minimum difference of density exists. fake gold bullion is never an alloy but usually a core of Tungsten (Wolfram) coated by gold. as the difference of Tungsten in weight/density varies only a tiny fraction from gold the discussed gauging instrument is indeed useless.

Well, if you do a little research, you'll discover that these ultrasound measuring devices measure the speed by which sound waves travel through the material, having nothing to do with density. Sound propagation velocity in tungsten is drastically different than sound propagation velocity in gold, which is exactly the purpose for using the device.

i did a little research and... i stand corrected

[apetley]

An ultrasonic gauging instrument only determines the thickness, it cannot determine if it is pure gold or an alloy.

but it can determine the thickness of two metals if a minimum difference of density exists. fake gold bullion is never an alloy but usually a core of Tungsten (Wolfram) coated by gold. as the difference of Tungsten in weight/density varies only a tiny fraction from gold the discussed gauging instrument is indeed useless.

Well, if you do a little research, you'll discover that these ultrasound measuring devices measure the speed by which sound waves travel through the material, having nothing to do with density. Sound propagation velocity in tungsten is drastically different than sound propagation velocity in gold, which is exactly the purpose for using the device.

i did a little research and... i stand corrected

Gobsmacked!

[Aussieroaming]

The easiest way is to do exactly what is done before bullion is shipped to the mint. Get a small bore drill bit and drill out a sample core. This is easy and there are no losses for either party. You can visually inspect the drill swarth and then can also do an independent bullion assay which will give you the gold purity if it is an alloy.

This is speaking from personal experience

[fletchsmile]

Ironically the thought did occur to me given where we are: How you going to know whether the machine you buy in Thailand is fake or not

[Naam]

The easiest way is to do exactly what is done before bullion is shipped to the mint. Get a small bore drill bit and drill out a sample core. This is easy and there are no losses for either party. You can visually inspect the drill swarth and then can also do an independent bullion assay which will give you the gold purity if it is an alloy.

This is speaking from personal experience

i can vividly imagine the benign reaction of a goldshop owner when a potential customer arrives with a drill and demands to drill holes in goldbars

[gk10002000]

The easiest way is to do exactly what is done before bullion is shipped to the mint. Get a small bore drill bit and drill out a sample core. This is easy and there are no losses for either party. You can visually inspect the drill swarth and then can also do an independent bullion assay which will give you the gold purity if it is an alloy.

This is speaking from personal experience

I doubt the average Thai seller will let you core drill a section of his gold bar.

[rak sa_ngop]

The WJT Group shop located on Mahesak, close to the Holiday Inn on Silom Road, have several electronic gold testers listed in their catalogue but not much info on which basis the machines work. They supply to the gemstone and jewellery trade.