If you have a self healing mat, they love water. It says that you can soak them in a tub of water. I have an olfa and put mine on my dining table with a towel underneath. I got a brush ( one that is circular and has a place to put dish detergent in the top of it) and took water with the soap and gently went over the whole board. Let it sit a few minutes, then with a cloth, went over with clear water and left it to dry. Then used my quilting sanding disc over the mat and it's like new