Beer with Foam on it

By Anupum Pant

Think about this. You have a glass full of water, with water nearly till the rim and then you have a mug full of beer, with its foam almost reaching the edge. Carrying the glass full of water in your hand from one end of the room is clearly more difficult than carrying the mug of beer that has foam in it. I have always thought that this must be due to the difference in viscosity of both the fluids. But what if one had beer with no foam and other had beer with foam in it?

Turns out foam plays a big role in determining if the liquid spills on shaking the container, or not. It’s much easier to spill beer with no foam on it or even a glass full of water, or a glass full of coffee (with no foam of course). But when you have foam on your drink it is much harder to spill it.

That is because walking with a liquid that has no foam on it lets the waves propagate easily, without any resistance. However with a liquid with foam on it has to go through the resistance from the foam to propagate waves on its surface. This makes it harder for the liquid to spill.

Some researchers at Princeton university are studying the actual physics involved in this “anti-sloshing mechanism” of foam on liquids by studying the motion of foam bubbles using a high speed camera.

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