So I thought I'd share this with you guys since its a pretty neat application of science on confirming that your metals are real. As I posted a couple of days ago, I ordered a 1 Oz gold bar from a non reputable source. It was a good price, so I figured I'd give it a shot, why not? Why I was able to take that risk, is because I could perform a foolproof test on the bar. Attached are pictures and explanations of whats going on.
So here is the bar I ordered:
It came in standard packaging, inside of the Assay card with no obvious defects or signs of being a forgery. A real pamp bar is 42mm x 24mm x 1.7mm. The bar when measured with the calipers was 42mm x 24mm but I couldn't determine the height because it was inside of the packaging. It looked a little bit thick, and the weight was about 1 gram lighter inside the packaging than it should have been. When you get a real gold bar that says 1 troy ounce, it will be exactly 31.1 grams not 30.9 or anything remotely off of 31.1. However, since it was in plastic packaging, it was measuring 36.9 grams and online sources said it should have been about 37 and change. I was suspicious enough to remove the gold bar from its packaging (completely ruining the premium, but oh well).
My handy dandy testing tools!
A digital calipers and an Ultrasonic thickness gauge. The calipers are used for very precise measurements down to the fraction of a millimeter. The ultrasonic thickness gauge uses ultrasound waves to read the thickness of an object.
How it works:
The probe is zeroed and then the sound velocity is set to 3240m/s. That is the speed at which sound travels through gold.
The probe is then coupled to the metal using Glycerin, and it uses the speed of sound specified to calculate how thick the thing you are measuring is. The reading there shows 2.9mm.
A quick check with the ole calipers shows that the bar is actually 3.88mm thick. If it was real gold all the way through, the ultrasonic thickness gauge would have displayed 3.9mm instead of the 2.9mm. Therefor, the bar is completely and utterly fake. As you have noticed its all scratched up. I wanted to see how thick the gold plating was, and it was actually quite thick. It was an incredibly good forgery, not a $5 chinese made bar, but it probably cost $100 or better to make the fake bar.
And here is a real 1 oz silver Canadian Maple being tested. Its a little bit trickier on coins so I got a little bit of error, but with a tiny bit of common sense it confirms that the coin is real.
The Ultrasonic Thickness gauge is adjusted to 3600m/s the speed of sound through silver. A reading of 2.9mm, lets see what the calipers say.
About 3mm. So I was off by a 3% margin. Why is that? Oh, because there is a .5ish mm lip around the edge of the coin. The thickness gauge needed a flat surface to get a reading, but the coin's rim is raised by about half a millimeter on either side of the coin. Righto all checks out!