I've held some 10-ounce Johnson-Matthey gold bars for a while now, and am considering taking a drill to them, simply to satisfy my curiosity. While I am not naive to assume the stories regarding tungsten-filled bars may simply be planted to discredit gold, there is simply no way to accurately assess whether the bar is or is not salted.
I can't be the only one considering this, but if anyone here has done this, I would like to know whether defacing the bar in this manner seriously devalues it, other than the weight of the removed metal. I would sell it as a 9.xxx ounce bar, were I to do so, but I was just wondering if anyone else has any experience with this.
From reading about the chinese tungstengold fakes, it seems they need at least 1/16" of real gold on the outside to pass the X-ray tests. However, I imagine anything built with a tungsten core would fail an ultrasonic test spectacularly.
In light of this, my preference would be 1 oz. gold coins, which are approx 1/8" thick, allowing no room for a tungsten layer, but if I were in the market for a 10 oz. bar, I would *absolutely* insist on drilling it in at least 2 spots with a 1mm bit (minimal damage). Buying a bar which was already drilled would not give me pause.
JackT, many thanks for your reply!
Would you be able to recommend an adequate UTG and the appropriate transducer for such an application (which would probably be used to assess silver ingots as well)?
( I don't want to know!)
Well, you won't need highspeed acquisition, data logging, or graphical displays, so I would think even the most basic model would do the job. All the major instrument suppliers have something to offer, but very little at the 'bottom end' of the market. That's where ebay comes in. :) Check this out for US$110 https://www.ebay.com/itm/New-Ultrasonic-Thickness-Meter-Tester-Gauge-Vel...
Just plug in the appropriate velocity for gold or silver and it will tell you the calculated thickness. compare that to observed values and there's your answer.
Hello again, JackT...
Thanks for your continued response. While the veracity is results using ultrasonic testing through the use of a thickness gauge is uncontestable, it only really works if the back and front planes of the item are parallel to each other. With poured bars and coins, this isn't really the case. For the JM bars I hold, the front is uneven from the pour and the back has had gold shot added in order to bring the weight to precisely 10 ounces -- and is therefore uneven as well.
Now, it's possible that my concerns here are unfounded... please let me know if you think so.
I also think that the solution to a lot of this is to produce bars with a gasket pattern in them, such that the material on the interior is visible, and to do this over the surface of the bar. This would serve two purposes: (1) It would eliminate the (relative) ease with which a blank could simply be plated, and (2) it would be a pattern that would be difficult to replicate accurately and minimize the amount of false material that COULD be introduced, making the effort unworthy of the time and cost required. I could be wrong about this though.
Continuing thoughts on this and similar matters would be welcome.
Kind regards... T1O