Why Does My Tongue Freeze to a Silver Spoon?

You've eaten really cold ice cream many times with plastic spoons and stainless steel spoons and never had a problem. Then one day you used a silver spoon and you panicked because you couldn't pull it back out of your mouth-it froze to your tongue! After a few moments, you were able to pull it out. Why did your tongue freeze eating ice cream with a silver spoon?

Good -vs- Poor Thermal (Heat) Conduction

Even as a good electrical conductor allows the free flow of electrons to occur, which we call electricity, a good thermal conductor allows the free flow of heat. Most metals are among the best thermal conductors. Non-metallic materials such as glass and especially plastic do not conduct heat so well.

Ice cream generally contains dairy products. Dairy products contain water. Water freezes at 32 degrees Fahrenheit. In order to make ice cream stiff the temperature would have to be less than 32 degrees. Why less than?

Antifreeze

This is because when other substances such as sugar are dissolved in water, the sugar acts like antifreeze. A car radiator with a water-and-antifreeze mixture does not freeze at 32 degrees Fahrenheit. In areas where temperatures are likely fall as low as minus five degrees, a certain amount of antifreeze must be added to prevent freezing. In areas where the temperatures drop much lower, more antifreeze must be added.

Ice cream contains a lot of ingredients that act like antifreeze. It takes a temperature considerably below the freezing point of water to keep it frozen.

Heat Flow

Now let's get back to our spoon. A plastic spoon is a poor heat conductor. You can eat ice cream with a plastic spoon without fear of its freezing to your tongue. A solid sterling silver spoon, however, is an excellent heat conductor-one of the very best. When the spoon is dipped in a container of ice cream, the bowl of the spoon quickly loses heat so it reaches the same cold temperature of the frozen ice cream, which is well below the freezing point of pure water. If the ice cream has been kept at very cold temperatures, especially, there is a risk in putting it into your mouth.

There is usually only a small amount of saliva on your tongue, and that saliva is mostly water. Ice cream freezes at a temperature much colder than what is required to freeze saliva. Put the ice cream-filled silver spoon on your tongue, and the saliva immediately freezes your tongue and the spoon together!

Why doesn't this happen with a stainless steel spoon? Common stainless steel is not one of the best conductors. When a stainless spoon is put into the ice cream, it does not get as cold as the temperature of the ice cream, before you put it into your mouth. Likewise, the heat from your tongue does transfer as rapidly to the spoon, and the circulation of blood in your tongue quickly replenishes the tongue's heat.