Science Buddies: "Ask an Expert"

In my project, I plan to measure which moisture lotion best keeps moisture in. I plan to put water in small plastic pill bottles, and then put a filter on each bottle, and a differnt lotion on each filter. I plan to measure by weighing the container at different times.
My question is, what can I use as a filter. I want something that will let the moisture out, but won't let the lotion seep through into the water.
Any suggestions?

Well the first thing that comes to mind is a coffee filter. I don't know whether it's the best choice, but they are very cheap and you can just try it out quickly, see if it works for you.

I would imagine that some of the water contained in the lotion gets sucked into the filter paper, drying out the lotion layer. But then, isn't that what happens on skin as well?

Im with ivogougheschrich i think a coffe sorry if i spelled wrong filter would do the job.

How about onion epidermis - the thin layer of almost clear cells that is like a film when you pull sections of an onion apart.

Or perhaps tomato skin, but that would be more difficult to get a even thickness for each of your bottles.

Do you have a very sensitive scale to measure the water loss? or do you have a back-up plan for if the water level doesnt change enough to notice?
Maybe you could do a "pilot experiment" with one moisturizer and different membrane and filters to see which one works best?