It's one of life's little problems. You're all set to add some tomato ketchup to your chips, so you peel off the cellophane, unscrew the lid, give the bottom a few hefty pats, and... your dinner resembles a crime scene.
Well, if this sounds like a problem you have, Zoe Laughlin and science have the answer. If you give silly putty energy it becomes more solid but there are also liquids that become more liquid when you hit them, and ketchup is one.
It's all about shear thinning. Instead of treating the bottle like it has misbehaved, the trick is to apply the right amount of energy and sustain it in the middle of the bottle. As Zoe demonstrates, with a few taps of the side of the hand you'll soon be greeted with a controlled flow of the lovely red stuff!