Monday, July 8, 2013

Happy birthday handwashing

When you go to the toilets you wash your hands. At least it is expected. Mythbusters recently conducted an experiment in which they compared the bacteria residue of toilet users in which they compared 3 cases:

  • not washing hands
  • washing hands with water only
  • washing hands with soap
The results were exactly what you would expect. If you don't wash your hands, then you will host plenty of bacteria. If you wash only with water, you'll still carry a lot of bacteria, but if you wash with soap, it's ALL gone.

But if you want to wash your hands properly with soap, it's advised to dedicate a full 30 seconds to washing.  That's where Happy Birthday comes into the story. You may not have a watch since we live in the age of the mobile phone or your watch might be under your shirt's sleeve, out of sight while washing your hands. In this case, singing the song Happy Birthday (HB) twice will do the trick. Really, it does!

Something surprising about HB is that no matter if you're singing it properly, or a bit fast, or a bit slow... it always lasts ~15 seconds. Try it! Grab a watch or bring up the clock on your computer, check the time (in seconds), close your eyes, sing HB, open your eyes and check the new time! You can try it again, singing fast or slow. It feels almost magic.

There's a rational reason for this, of course. When you decompose the song, you find mostly 3 types of sound components:
  • short sounds: the very first word, "happy", is composed of 2 such short sounds
  • long sounds: the "you" of the 1st verse is such a long sound
  • pauses: respiration between verses and cuts, however short, that separate each word
When you sing fast, you only really modify mostly just the short sounds. While it does compress the song's duration, you are still singing the long sounds and pauses at a normal speed, and these account for most of the song's duration. 


  • Who would have thought that you can mix together toilets, happy birthday, and science in a single article?
  • Now you know the proper way to wash your hands.


  1. Important is the path, not the destination...
    Here the path is quite fun!!

  2. Hello Anonymous visitor! Welcome to my blog and I hope you enjoy the visit. If you have any comments, remarks, criticisms... don't hesitate! I keep this blog mostly for me but I'm open to suggestions if there's a need for change. Have a good day!


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