Quote Originally Posted by polyglot View Post
rbeech: do you have a model number or link?

Larry: I will probably test again with rubylith as I have a bunch of it. It'd be nice though if we could find a handful of widely-available known-good models that don't need additional filtering.

I also just tested some individual bright-red LEDs; very monochromatic and safe at around 650nm. They're not a readily-usable bulb module though.

Ghostman: if the LED spectrum is paper-safe, it will remain so. There is no filter that can fade or scratch and therefore become unsafe. The idea is that bandgaps in the LEDs are finite and therefore the right LEDs should be monochromatic with lower photon energies than the activation energy of the paper emulsion. The right LEDs are inherently safe for basically infinite exposure time, whereas a filtered incandescent will always eventually fog paper, even if it takes an hour or two because the filtering is not capable of cutting out 100% of the green/blue/UV output from a filament.

David: what is the voltage rating on those? I don't see anything on the webpage; is there something marked on the bulb or its packaging?
Interesting. Many thanks. I'll investigate this.