I watched an interesting video by artist Mark Mehaffey last evening. He painted a couple of watercolors on cotton watercolor paper coated with two coats of acrylic gesso. This allowed him to lift any color back to the white of the gesso. It also provides a great way to get some really neat texture in a watercolor painting. Today I gave it a try and must admit it was a lot of fun.
I probably be using this technique on certain paintings in the future.