Purity - LSD: Blacklight explanation saught

[Herbal Remedy]

Swim has had some blotters on him that he suspects may be an RC but are being misrepresented as lsd. Swim has read on this site that the use of a longwave Blacklight will tell swim all he needs to know. But swim being the way he is, he always likes to back statements up with facts before he bases his decissions on him.

Swim was wondering if any of you knowledgeable and experienced chemisty heads might be able to help him understand the reason why a blacklight can signify a presence of LSD on a blotter. Swim has used the search function but has only come across several statements saying it will work, but none that say why it will work. Swim understands if there is no easy answer, he appreciates any replies the community can offer... peace...