[nsfposter]

Ollie Deans  asked the Naked Scientists:
   
Dear Chris and the team!
 
I would just like to say how much I love all the Naked Scientist Podcasts, especially the kitchen science!

I would also like to ask a question which I think about every morning:
being rather clumsy, when I am dressed into my school jumper, and doing my teeth, (not at the same time) I sometimes manage to get tooth paste on my jumper... I immediately wipe it off, but later in the day it shows up as a mark, as if I had never wiped it off.

Although I am clumsy, when I wipe it off, it looks like it has all gone. 

Why does it reappear, and why won't it go away!?

What do you think?