Chmistry buffs: IR invisible ink?
I've seen invisible ink pens and things for sale that contain ink that show up in infrared, instead of ultraviolet light. That's really appealing to me for a number of project ideas because digital cameras pick up IR exteremely well (especially with their filter removed).
The problem is I think I'm going to want a lot of it, and those dumb little pens are crazily expensive.
So any of you chemistry buffs out there have a secret formula I could make? I'd prefer something invisible in regular light, but hey, whatever you've got. :)
Thanks in advance for your help,