I've got an old mat with a small crack in it and one big crack that is about 10" long. I soaked the mat in the tub (it's one of the smaller ones----18x24. Then I took it out, dried it and taped it heavily on the back. After drying it front and back, I discovered it still had linty stuff in teh cracks. Srubbed that a few times. It's now on the kitchen table with wet paper towels on the top. I don't want to get the tape on the back wet. I hope it holds together. We're probably going to need a second mat when we work at church tomorrow.