When painting watercolour with lighter weight papers (under 140lb) it is often beneficial to stretch your paper before painting on it so that it does not cockle when you wet it. By soaking the paper first and then stretching it, the paper shrinks as it dries producing a high tension accross the papers surface. Once stretched you will be able to wet the paper with washes etc without the fear of distorting your painting.
The Perfect Paper Stretcher is the revolutionary way to stretch paper in minutes. See the Perfect Paper Stretcher page for more information.