Fluorescent inks are regular inks crazy cousin. They are loud, enjoy being the center of attention, and need special care to get them to do what you want. Even though it takes a little extra work to get the fluorescents to cooperate, it's worth it in the end.
THEY NEED HELP
The first thing you need to know is that fluorescent colors almost always need help to get the job done. The only time they don't is if they are being used on white garments. The reason they need help, which comes in the form of an under-base, is that fluorescent inks are not as opaque as normal inks. The pigments in the ink can't fully cover the color of shirt on their own. This means the ink can't be its bright, vibrant self. Take a look at the difference between having an under-base and not.
IT'S AN OPPORTUNITY
Okay, that means if I want to use a fluorescent ink I have to pay for two colors?
Yes, BUT, you have a second color...USE IT! Having another color in your design is not a bad thing, it's an opportunity. Take a look at how we can take advantage of this color partnership. Pretty neat, huh?
It isn't necessary to have the second color make an appearance in our design...except when printing numbers. If fluorescent inks are used for numbers there HAS to be an outline on the number using the under-base.
THEY NEED MORE HELP?
Occasionally, albeit rarely, even the Fluo Duo needs help. Sublimated garments, their toughest foe, make it necessary to tag in a third comrade, Mr. Dyno. Without getting too sciencey, the dyes in sublimated garments don't like heat, it breaks the bond holding them to the polyester fibers. When the plastisol inks get dried they go through a hot conveyor which can potentially dislodge the dyes causing them to make their way into the ink, ruining the print. The dyno under-base stops those pesky dyes and keeps the print looking just the way it should.