Chris -
These is a great question, and I can hopefully give you some ideas.
First of all, if you have a container of water that is covered with
something like saran wrap, the water is not going to evaporate very
much regardless of the color of the plastic, since the plastic will
keep the water vapor from escaping. But since I don't think that's
really what you're asking, here's some other thoughts...
Water evaporates depending on its temperature. (i.e. Higher
temperature -> faster evaporation.) If you took two dishes of water
and put a colored filter over one and put them in a dark oven (assuming
that the filter itself doesn't stop the water from escaping), the color
of the filter shouldn't matter. Both dishes of water will be the same
temperature, so they'll evaporate at the same rate. Even if you did
this in a lighted oven, you probably wouldn't see any difference. It's
not the /light/ that makes the water evaporate... it's the /heat/.
But let's say that you set two identical dishes of water in the sun
in two identical windows, except that one window is clear and the other
is tinted blue. I would expect that the one in the clear window would
evaporate faster (try this at home to check!). Here's why: We know that
water will evaporate faster under a sunny window than in a dark room,
since the light from the sun is warming the water up. So the more light
there is, the warmer the water will get.
White light (like from the sun) is actually a mixture of all
different colors of light. It has some light waves that are blue and
some that are green and some that are red, etc. They only look white
because they're all mixed together. When you put a colored filter (like
the blue tinted window) in the way of white light, it only lets one
color of light get through. So only the blue light will get through the
blue window and all the other colors will get lost. As such, there will
actually be /less/ light coming through the colored window than the
clear one. Less light means that the water will be warmed up less, so
it won't evaporate as quickly.
The best way to settle this question is to do an experiment. Please try it and tell us what you discover.
-Tamara
(published on 10/22/2007)
