[thedoc (OP)]

Jacqui Clucas  asked the Naked Scientists:
   
Hi there

A colleague of mine at work told me that you did a fantastic experiment about sun tan lotion at the Rand Easter Show recently. My 9 year old son is very keen to look at doing this as his science project. Do you have an article or a youtube video showing how you went about the experiment and its conclusion?

Thanks a million!

Jacqui

What do you think?

[CliffordK]

This is a little older, but is this the experiment you are referring to?

http://www.thenakedscientists.com/HTML/content/kitchenscience/wierd/light/exp/how-does-sun-cream-work/

[cheryl j]

What would happen if you put sun screen on a leaf?

[CliffordK]

What would happen if you put sun screen on a leaf?

Most interesting question. 
Many greenhouses actually have a UV coating, in part because plastic doesn't hold up well to UV, but also plants apparently don't grow effectively with UV light. 

One could try growing two plants, one behind a UV glass (or plastic), and one behind plain glass (or plastic).

As far as sun screen.  If it is generally clear, then it would likely let through most of the light.  The Zinc stuff reflects light.  So, the UV protection should not be a problem for plants. 

The oils in sunscreen, however, could be a significant problem for plants.  If you would be trying an experiment with sunscreen, try to match a hand lotion or cream without sunscreen for a "control" group.