Actually, it's laundry detergent, and this is a real phenomenon, I was saying in another thread that we used to do it for fun in this lab I used to work at. The phosphates in the detergent make it glow under UV lights (black light is a sort of UV). You can actually do this... you can see a very faint outline under normal lights, though I don't think it would allow you to paint in detail without overlapping and messing up much, even with a "photographic memory" as Radzinsky had. One theory I had was that the UV may have served a practical purpose in this station that was marked "quarantine"; since UV can also be used for germicidal sterilization; and maybe Radzinsky/Kelvin were just taking advantage of this property that was already there.