[cmiluvustu]

Would it be possible to create an ink that is skin safe and changes colors once under UV rays? Ingredients would need to include Trolamine Salicylate and Benzyl Nicotinate, right?

Thanks,
Connor

[bosox99]

any highlighter that says "fluorescent" will glow under UV. Will that work?

[Arkcon]

Ingredients would need to include Trolamine Salicylate and Benzyl Nicotinate, right?

I don't know why you picked those two reagents -- if you're sure they'll work, then what's the question?  If you think they won't, then why limit to only those?  They're both topical analgesics, so why mention pain-killers as if they were dyes?

[Intanjir]

He wants to make a tanning lotion that glows under UV light, I think. It is dark enough inside those things that you could see the fluorescence, and those two substances, particularly the nicotinate, are used in tanning. He is looking for a third substance to add for the glow.
And yes it is somewhat possible, maybe. The trouble with it is that a material glows under UV light by converting that light from UV to a visible wavelength which causes no tanning. So either you use only a small amount of it and it glows weakly or you've just jumped in the tanning bed after slathering yourself in sunblock, which kind of defeats the purpose. Not knowing the numbers here I couldn't tell you if it is plausible that there is a 'just the right amount' that would work.

[Enthalpy]

"Change colour" is not "glow".
Such an ink could tell the user that he has absorbed enough UV for the day and better leaves the beach for the shadow.
Though, I'd prefer an electronic dosimeter, which advantageously wakes the user up. Powered by solar cells.