On Elise Blaha Cripe's Blog enjoy it she posted a 2 part series on how to water marble using nail polish.
I had to give it a try, and I love the results.
I tried 2 odd-sized glasses and an unfinished terracotta pot. The glasses were dipped stem first so no paint got on the inside. I then used the nail polish remover to clean the bottom of the glasses to create a smooth surface.
With the pot, I would put it into the liquid slower next time. The air bubbles that were created made little holes all over the paint. I might not be able to get around that though with the hole in the bottom of the pot.
I am going to experiment more this weekend. I have already learned a few things (like keeping the nail polish remover close at hand and not to use warm water - it makes the nail polish clump). I am looking around my house for more things to dip!