Originally Posted by HouseDragon

From Sew Fantastic blog:

(This info is directly from an olfa dealer).

Directions :: Fill your bathtub with room temperature water (not hot, not warm, and not cold) In the water add 1/4 cup of white vinegar and a squirt of dove dish soap for a good lather. Use a mushroom brush (soft bristle brush) and scrub the mat gently getting a good lather with the soap. Then rinse your self healing mat with cool water getting all residue off the mat. You can dry it with a cotton towel, or air dry. It does not matter how you choose to dry it. (Do not dry it in direct sunlight or it could damage the mat).

The reason for this method is the materials that make your self healing mat absorb the water and make the mat supple again. Not only does this make your mat last longer, but it keeps your blades from dulling so quickly because you are cutting into a softer surface. Makes sense right?

If your mat won't fit in your bathtub, use a child's wading pool: inside not outside. After soaking, dry both thoroughly, put the mat back in the pool and let it finish drying on a flat surface inside your home.

I've also read that you should soak your mat every four-six months. So if you've had your mat for years, it might take more than one soak to do any good.