Once I accidentally ironed something on my mat. The mat didn't like it and warped immediately. It was one of my favorite mats, and I couldn't bear to throw it out. I put it on a table and put some heavy things on top and forgot about it. After a good amount of time I remembered and to my surprise it was flat again. It is an Olfa green mat and is many years old. I now have two and both are my favorites. They seem to last forever.
Sue