I recall that water is 1.3 (about) and glass is 1.6 (about) air is (about) 1.0. Starting to sound like Snell's Law - wish I could find my optical mineralogy book. I left the water out as I was interested in the glass (and I didn't think of it)- besides this was a "quick" render done in about 20 minutes (or it would hsve been if I hadn't had to do everything twice.) In 3.1 couldn't set TIR - I am chafing at the bit to try TIR. Perhaps on the weekend - TJ