Windex has ammonia on it. Don't NEVER-EVER-EVER use ammonia on acrylic (Plexiglas). Our boat was 10 years old when we bought it and all the acrylic was shot. There were fracture lines deep into the material. The boat was spotlessly clean when we surveyed it and we found 4 bottles of Windex stashed around the various compartments. The line in caps above was the advice I got from Multi-Craft plastics when I bought the replacement material. That was his comment after one glance at the old port I brought in.