One of my email correspondents and botmaker, Bill Sherman, had made some Joule Thiefs inside of a jar, but this Instructible uses diluted fluorescent ink from a Highlighter pen to diffuse the light into various colors. That’s quite a nice idea, and gives the light a very dispersed and colorful look.
What I would like to see is some fluid that has the same properties that the phosphor has inside of the white LEDs. I could put a bright blue LED inside of the fluid and it would glow, radiating whatever the color the fluid happened to be. My guess is that since it’s a fluid, it may not be stable and long lasting. In that case, the fluid might be changed to a clear liquid that hardens, such as casting resin. Just mix up the fluorescent stuff in it, and catalyze it, insert the LED and wait for it to harden. Maybe one could just use a Highlighter pen to stir the resin, and enough of the ink would dissolve into the resin to do the job. One concern would be that if you ever had to change the LED, it wouldn’t be easy! I suppose it could be drilled out and a new one inserted into the hole. But hey, it doesn’t cost that much to make a whole new casting.
Back to thinking up some more wild ideas…