Aspen is no where near as absorbant as paper towels. Use a thick brand like Viva, and put a couple of layers. Aspen unfortunately lets the pee go straight to the bottom of the tub, where it will dry later on. Papertowels soak it right up if you get a good brand.
Right. Just like that old science experiment you used to do where you'd hang the tip of a piece of paper in a cup of water and after a little while the paper soaked the water up against gravity. The paper towels absorbed the liquid across their surface area making it look like much more liquid was expelled than when she used to go on aspen. Thanks for stopping my worries.

Dennis