Ok, this isn't exactly camera-related, but I've been told there are a lot of IR afficianados here. If it gets moved, I understand completely and apologize for any inconvenience. I'm working with my college professor to build some engineering kids for school students. The 10th grade kit involves building a "burglar alarm" using infrared. The prototype works really well - break the beam, and the buzzer sounds. The thing my professor is interested in is finding a way to "show" that the infrared light is there. I was wondeirng if there is any material that can react and show that there is IR light present. They sold these beads and paints that would react to UV light and change color in the sun, I'm curious if anything like that exists. The only other thing I can think of is building a little "black box" with a thermometer and having that show a temperature increase when the IR light from the transmission LED. I did a google search but didn't find anything really good. Any advice would be greatly appreciated by my team.