I appreciate your answer, especially from a photographic point of view, and I know the technique with colored reflectors, I first saw that in the YT video of Karl Taylor where he photographs the whisky bottle. Have never used it myself though. - The projects I'm having, however, are about the decorative purpose, so they should look nice in my flat and in the hand ;)

I am not sure about that. The alcohol might not, but the sugar and other ingredients might be. I don't have any experience in this field. But if it rots away, I'll be sure to note it down here. First I have to get some pastis, though ;)

@Stan: I want it to be liquid because of the attraction that glowing liquids and a chemical look have to me. The same reason the thick glow sticks always make me wanna touch them ;) And thanks for your encouraging words!

@Ghost: in my particular case that is a great idea. I'll give it a thought. The rgb led solution might be preferred because I can fade them from green to red ;)

Thanks for the input. I wrote a comment on the question to clarify the use in response to the usage question. It needs to be liquid. But maybe pva glue is somewhat soluble in water (or another liquid).

I want to use it for at least two projects in which I want a fluid to look like it is radiating light. The straight forward one is a jam jar standing on an insuspicious surface which has a (hidden) rgb led and an arduino in it. I realized this with the soapy water and got some nice reactions. The second one would be something that should resemble small laboratory vials that look like they have a radioactive substance in it, by lighting them with a green led. Those would then be fixed and the led would be inside the water but hidden from sight. Let's hope this works ;)

Can the downvoters please comment on why they downvoted?