I put an old mat in the back of my SUV for quilt camp, but when we got there I didn't need to use it so it stayed in the car for 4 days. Well, needless to say it was hopelessly curled. When I got home & was unloading stuff I just threw that mat out on the patio thinking I would worry with it later. Was I surprised to find it was nice & flat the next day. I still can't figure out why it curled in the heat of the car & uncurled in the heat of the patio. Go figure!