if your mat is a self healing one you can soak them in the bath tub and use something soft like a mushroom brush. Self healing boards love water. I have a shower, no room to soak in tub. I instead put a towel underneath my mat and using the brush and squirt of detergent put it all over my mat. Let it sit for about 20 min, then did the same thing with clean water. Left it laid out to dry, then used cutting mat sander and believe you me, Mat is beautiful, just like new and rotary cutter is working great!!