Supposedly if it is a "self healing" mat, they say to soak small ones in the bath tub in warm water for 20 minutes and let it air dry flat. I am trying my mat - 40 X 72 - by pouring a small amount of water and rubbing it around and letting it air dry. Mats too big for the tub I would do the same way. First clean it with a little mild detergent and a light abrasive spunge to get the threads and such that have gotten in the cuts. Once it is clean, wet it and let it sit.