I have used 300lb watercolor paper for most of my painting career but have recently started using 140lb. I used
300lb because I like that it never wrinkled and I was too lazy to soak it, stretch it and staple it to a board and then let it dry. That was always too much work for me. Now I have a simple tip to use 140 and 90lb watercolor paper instantly with no wrinkles. See Video Below.