As I understand it, there's no need to soak it, just lay it in a bath of warm water with some mild detergent or liquid soap and scrub it gently with a soft brush. Rinse with fresh tepid water and dry flat on a towel NOT in sunlight or near a direct heat source. Mine are 24" x 36" as well and I just let them roll gently up the sides of the bath while I clean them then push them gently too and fro in the water. When they're not left there for any length of time, it does them no harm. I have two different brands, treat them both like this and they're like new. :-D