Why do Olympians bite their medals?

According to four time Olympic medalist Summer Sanders, mainly because the photographers incessantly ask them to until they do it, usually at the end of the podium photo shoot sessions.  The tradition probably stems from the age old practice of testing whether something was really solid gold or not by biting it.  

Gold is a very soft metal, at least softer than tooth enamel, and if it’s fairly pure, you should be able to leave some teeth marks in it by biting it.  The practice of biting precious metals also allowed people to see if perhaps the gold object was really just gold plated, with something like lead at the center.  If so, the gold plating could be scraped off with your teeth and, given the often bitten gold coins weren’t that thick, the plating tended to be fairly thin, so you didn’t have to bite too hard to discover whether it was relatively pure gold or not.

Obviously Olympic gold medals today are not made of solid gold (not since 1912, though they do have 24k gold plating).  Rather, the gold medals are made mostly of sterling silver.  But were you to actually bite down on the gold plated silver Olympic medal, you should be able to make a dent as silver is also softer than tooth enamel, but harder than gold.

Using Mohs mineral hardness scale, we see that tooth enamel is rated at a 5, while gold is rated at around 2.5 and silver at a 2.7-ish.  Tooth enamel is also higher on the scale than copper, which the “bronze” Olympic medals are mostly made of, so it’s possible to make teeth marks on those too.

Mohs hardness scale is a relative hardness scale created by German geologist Friedrich Mohs in 1812, rating things based on scratching one material against another, the one that makes a mark on the other is rated as  harder.  If both scratch each other, they are considered to be the same hardness.

For reference, glass is rated at 5.5 and tooth enamel is actually slightly higher than steel or platinum (at 4-4.5).  (Note: just because something is only slightly higher on this particularly scale than something else doesn’t necessarily mean it’s only slightly harder.  For instance, diamonds are rated at a 10, while corundum is rated at 9, but diamonds are 4 times as hard as corundum.  Further, corundum is twice as hard as topaz, which is rated at an 8.)

Despite the fact that none of the athletes are actually trying to make marks on their medals or checking for authenticity, the tradition with Olympians has endured and photographers simply won’t let it die as it makes a more interesting, “playful” shot over an Olympic medalist simply holding their medal up next to their faces or the like.