Thanks Joanna,
I might try the newspaper. I use cardboard because it's easy to lift out when adding food. I have a spray bottle and usually give the bedding a good spritz every day or two. The bedding gets pretty dry on the bottom while the top remains fairly moist. I have a flow-thru bin with cardboard covering the bottom and about 6" of bedding which is more shredded newspaper than cardboard so that may be contributing to the evaporation issue. Here's an inside view of the bin.
