I use Surface RT tablets in my classroom. Some of the tablets have Type Covers, some have Touch Covers. Sometimes, a student will mark the cover with a pen, such as in the attached picture. They will tag the Touch Covers more often, because they are a bright blue and felty. My question is, how do I remove the ink from these covers? I try using Isopropyl Alcohol, which does help fade the ink. Just wondering if anyone has any other ideas.