Hi everyone, welcome back to Cody's Lab!
So, a long time ago back when I did my biting indium video
a lot of people posted comments saying that I should try biting some gold.
because, apparently, one of the things people do in order to
confirm that gold is authentic is to take a bite out of it.
You can see this quite often in photos of Olympic gold medalists of noshing down
on their Olympic awards. And as it happens I just bought a one ounce gold
bar using my last paycheck and so I thought why don't I give it a shot
and see if I can determine it's authentic?
Well first of all came with an assay certificate so I'm fairly certain came
from a reputable source but I'd also gone through the trouble of measuring its density
and it does have the correct density
however there could be a tungsten core in here, right? I doubt it because it's so thin, I mean,
someone probably wouldn't go through the trouble of putting tungsten core in a bar this size
but if there is tungsten there the gold would be very much harder than would be
normally. Got a piece of tungsten here. Tungsten is a very hard metal but
gold is a soft metal. I don't think I could dent that with a pair of pliers. So let's
try biting this bar and see what happens
so I was only able to dent it just very slightly
there's definitely a dent there but it's nowhere near what most people would
expect so does that mean that this bar is fake? So to find out how about I take
a piece of gold that I know to be absolutely genuine because i actually
refined this myself - thinking episode two or three of my refining series. But anyway
this is pure gold
so let's take a bite out of this and see if it has similar results
yeah, I'd say that bite mark is almost exactly the same size so that means the
gold bar is actually genuine 'cause they were about the same when I bit them. See a lot
of people think that gold is very soft metal almost like butter
where as it's actually about as hard as aluminum. You can see this aluminum
muffin tin that I cut apart. If I take a bite of aluminum
You can see that i get about the same
size dent. Gold is a soft metal compared to steel or tungsten but it is actually quite
hard compared to a lot of other metals such as lead or, of course, indium but I was
actually able to put a small dent in this gold so perhaps it is a good method to
determine if it is genuine or not so i have this gold bar here which is actually a fake
fake gold bar that I bought off eBay. This is supposedly contains a thin coating of
gold on the surface but it actually doesn't even have that it's solid aluminum-bronze.
I even cut corner off of it to do further tests and I've confirmed there's absolutely
no gold and these things are all over eBay so watch out for them
but let's take a bite of this.
You see I have dented it vary slightly but it's
much less than the gold is dented. That's because aluminum-bronze though having a
gold color to it is quite a bit harder. Now
Olympic gold medals are actually a thin coating of gold over pot silver so let's
think about the silver bar here to see what kind of dent it makes if that's the case
ok so just slightly larger than the aluminum-bronze. Silver and copper are about the same
hardness. Here is a gold coin which I've actually made and is fake
this is a piece of steel coated in 24 karat gold you can easily determine that
this is fake just by bringing a magnet near it but let's also try the biting test
Yeah, there's no way I'm denting steel. There is one way, of course, that I can soften gold. This
gold bar has been worked hardened.
The act of punching it into the bar shape has actually hardened the metal
See because it puts strain in the crystals of the gold and it increases the strength
of the material, but if I heat it up I can relieve that strain and the gold
will return to its softened state.
So let's actually do that and see if it makes
any difference to how it is with biting it.
There we go. I heated the gold up till its a bright red hot which is just a
little bit below its melting point so that I don't have a puddle of gold on my
hands and I now as I let it slowly cool off
it should form the unstressed crystals of the soft gold. This is of course
another way you can determine the gold is genuine because a gold bar that is fake
would oxidize. Gold does not oxidize even at high temperatures so if i take this fake
gold bar here and do the same thing to it.
You can see that the bar is actually severely discolored now.
In fact just as I'm holding it you can see it oxidizing in the air
It's forming the copper oxides. I need to find somewhere to put this.
There we go. This gold bar has almost cooled down to room
temperature. So another cool thing about gold is it cools off very quickly. Let's take
another bite out of this and see if there's any difference
Oh yeah most definitely. I was able to take a much larger piece out of that. I wasn't able to
bite it off at the dent is like 10 times bigger and finally I have here
some gold dental crowns that fans sent me using the address in my about section
on YouTube. This is actually the biggest donation I've ever gotten to my channel
because these weigh about 4 grams each and they're about 60-percent gold with the
balance being silver, copper and palladium. That fan wishes to remain anonymous but if
you're watching thank you very much i'll definitely be putting to use my videos
but what I have them out for is the fact that gold when alloyed with some other
metals actually becomes quite hard and you can take advantage
of its properties where it's inert and it actually makes very good dental
material so you can bite gold or you can bite with gold. So hope you all enjoyed
I'll see you next time.
Now that I've softened the gold bar by heating I should actually be able to
bend it just with my hands and indeed I am
So I've pretty much ruined this bar now but
It's still valuable due to its weight I just can't sell it for the coinage premium.