I almost ruined my main yoga mat.
I’ve been using the Manduka eKO line of yoga mats since mid-2007. Heavy and bulky, I take it to class at Thrive Yoga when I can dump it in the backseat of my car. It’s not something that you want to carry around to and from class. It supposed to “last forever” and be eco-friendly.
A few summers ago, I left it in the car while parked at the Metro station several days. Bad idea. The exposure to heat and sun light started degrading the rubber (Manduka instructs you not to expose the mat to the sun for extended time). I also made the mistake of rolling it up with the top surface exposed, rather than the tougher base facing out. The result was that the mat lost its stickiness and grip, as if the rubber began to oxidize and harden, becoming discolored and slick. In class, my feet and hands began to slip in downward-facing dog, especially once I had worked up a sweat, and I knew I had to do something about it.
The solution was similar to removing rust from metal: I used a fine-grained sand paper to remove the crusty surface to expose a fresh layer of rubber. When I finished sanding the surface area that had gotten exposed (about a quarter of the mat), I realized that the rest of the surface had also started to degrade, though not as badly as the sun-damaged part. I applied the sandpaper to the whole mat. I then washed down the mat to remove the loose powdery substance resulting from the sanding. Once again, I had a good grip on the surface.
I suspect there is a limit to this method because I will eventually work my way through the top surface. Manduka has made design changes and introduced new technology to their yoga mat lines, including imprinting patterns in the top surface so this sanding technique would remove that feature.