Black lights occupy the lowest and least visible spectrum of light, and as such, they do not compete well with other types of light. A black light will only work well if there is no other light present in the area being lit.
It's also important to note that it takes a lot of power to create a small amount of black light. Incandescent black lights are not nearly as powerful as fluorescent black lights, due to the fact that fluorescent lights have a built in transformer that allows the "power" to be stepped up considerably. Incandescent lights are rated according to how much power they use, but a 150 watt black light will not be nearly as bright as a typical, white 150 watt light bulb that you might use in a table lamp. Fluorescent bulbs also have a much longer life than incandescent bulbs. The average fluorescent will last around 10,000 hours, but the average incandescent will last around 300 hours. These are not guaranteed times, but are based on sample calculations from a batch. Fluorescent bulbs require a special rapid start transformer, so they can not be used in standard fluorescent fixtures, but must be used in fixtures rated for blacklight use.
If you are lighting an object or area with black light, it's important to note that you should use as much black light as is practical. There is almost no such thing as "too much" black light.
Blacklight bulbs do not typically last very long outdoors unless they are protected by a glass or acrylic lens in an approved weatherproof fixture. Since the bulb has a UV coating, it gets very hot, and moisture can cause the bulb to burn out quickly. Fluorescent bulbs do not get hot and will weather much better, but no fixture should be used outdoors without GFCI protection.
Paints and Inks are not returnable, as they cannot be re-sold as new.