I picked up a GE UCF13/EB/DX 13" (Thrift-Store Score $1) Fluorescent Under Cabinet fixture and I plan to use it as a blacklight fixture. I already had a F8T5/BLB lying around from another fixture whose ballast fried. I have a question though what is the difference between BLB and the BL fluorescent lamps. Is there other differences other then the color of the glass or phosphors as I noticed that the /BL is white and the /BLB has a purple color to it.

Thanks

BL is made out of clear glass, and lets out a lot of blue visible light as well as UV. BLB is made of Wood's glass which is deep blue/purple and filters out most of the visible part of its emission, so the lamp emits more UV than visible light. If you want to light fluorescent paints with this lamp, then you would use BLB so there is less visible light, and the fluorescence will be brighter. BLB is also used in counterfeit detectors for money. BL lamps, on the other hand, will make fluorescent paint glow, but the visible light emitted by the lamp interferes with the vision when looking for the fluorescent effect. BL lamps are used most notably in insect traps where the visible light also helps in attracting the flying insects.

OK thanks I just want it to illuminate my fluorescent posters and not the room so I think I will stick to my F8T5/BLB bulb then
Thanks for the quick reply

Yes, the BLB is the best choice for that application.