What is Gold Karat Purity? Explained with Coffee Drinks

Karats with a K refers to precious metals purity where Carats with a C is used for diamond weight.

Transcript for the Gold Purity Explained with Coffee Drinks video

Welcome, my name is Michael, from the United States Gold Bureau. Today, I’m going to explain the unit of measure for gold purity, called the “karat,” by comparing gold to iconic coffee drinks that you’re probably already familiar with.


Did you know? Karats with a K refers to precious metals purity where Carats with a C is used for diamond weight?

In my coffee shop, I’ve got an espresso machine, a couple of glasses and the ingredients to make a macchiato and cortado. I’m going to use these drinks to show what we mean by karats of purity when it comes to gold coins and bars.

For the sake of this explanation, let’s assume that one espresso shot, is comparable to 1 oz of pure 24 karat gold. Karats are simply an expression of the purity of the gold, using a base of 24 units. 24 karat gold is 100% pure. 12 karat gold would be 50% pure, since it’s 12 24ths pure. Other common karats are 18 karats (75% pure) and 22 karats (about 92% pure).

Now let’s use the visuals to explain this a little better. Let’s start by pouring one espresso into this glass. As we said, in this experiment, one espresso shot is comparable to 1oz of pure gold.

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Now, I’m going to add a small part of foam. The result is a glass that contains 1.09 ounces of liquid which, don’t forget STILL has a full ounce of espresso included in it; I didn’t take any espresso out I just added something else to it. This mixture is comparable to the 22 karat Gold American Eagle coin, the Krugerrand, or other popular coins.


These 22 karat coins actually weigh MORE than a 24-karat coin, since they contain a full ounce of gold, PLUS the added “ingredients,” which in the case of our gold coin, is an alloy of copper and silver combined.

And just like adding a bit of sweetness and flavor makes espresso smoother to drink, adding a bit of copper-silver alloy makes the coin more durable and less susceptible to tarnishing or scratching, since, as you may know, pure 24 karat gold is actually pretty soft and can be marked up fairly easily.

This next part we’ll turn this macchiato into a cortado by adding about another ounce of foam to our little concoction, so I can show you what 12 karats of purity would look like.

Now, I’ve got 2 ounces of liquid, including 1 ounce of pure espresso that just happens to be mixed in foamed milk that we added a moment ago. This mixture contains 50% espresso and 50% foamed milk, which, based on what we’ve learned, would be 12 karats, or 12 24ths of pure gold.

Thank you for joining us today. For more information on purchasing precious metals use the information on the screen.


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