Blacklight (BL) lamps are made with a
special glass that filters out most visible light. Blacklights instead
emit a specific type of ultraviolet light called UVA. Blacklights
are good for making certain substances glow that would normally be
invisible.
Blacklight Blue (BLB) lamps are designed with
a special deep-blue glass that does a better job of filtering out visible
light than regular blacklights, producing the maximum amount of ultraviolet
light possible.