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Why does runny honey stop dripping when there is still plenty left on the spoon?

David Muir
Edinburgh, UK

There are two competing forces at play here: viscosity and gravity.

Gravity is pulling the molecules in the honey downwards and causing them to separate and start flowing. On the other hand, intermolecular forces between the particles within the honey resist the flowing motion, and the viscosity of the honey is directly proportional to their strength.

The honey stops dripping when the intermolecular forces between its molecules overcome gravity. The intermolecular forces in petrol (gasoline), for example, are much weaker, so it is much more runny than honey.

You can see the tug-of-war between viscosity and gravity with water. Fill up a bottle with water to the very top. Keep adding drops of water until the meniscus, the curve on the surface, protrudes above the lip of the bottle. At that point, viscosity is in ascendancy. Add a few more drops and gravity takes over.

Mark Thompson
Tewkesbury, Gloucestershire, UK

When I was a wee lad my mum was fascinated by the honey dipper and spoons.

We kids loved it because she would toast muffins and try to fill the individual holes. All I can remember is the dipper almost always caused the holes to fill, the spoon less so – so the fight was on to have the dipper muffin, yum!

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