Fluorescent ink pigments have the ability to absorb ultraviolet energy and re-emit this energy in the visible spectrum almost immediately. This causes them to appear very bright in daylight conditions.
Special considerations for fluorescent inks include:
- Best when printed on a white or light background, which acts as a reflector base and enhances the fluorescence.
- The level of fluorescence is proportional to the ink film thickness (consider a double-bump for best results).
- Fluorescent inks are semi-transparent and are weaker in strength than conventional ink. Their mileage is typically lower.
- Fluorescent inks have poor light-fastness and will fade in a shorter time than conventional inks.
Metallic Inks overview
Metallic inks contain metallic particles including copper, aluminum, bronze, or zinc. After printing and left to dry, the metallic particles rise to the surface; reflecting light and creating a metallic sheen. Metallic inks show the greatest effect on less porous stocks. Metallic inks are more opaque than conventional ink and have a good hiding ability.
Light Inks on Dark Stocks
Lighter colored inks will typically not show up well on darker stocks, the color tends to shift or become "dirty". Sometimes the addition of Opaque White (up to 20%) will give you an acceptable result, but oftentimes the color will still not be what you're after. Other things to try are laying opaque under the color, if you can double-bump it that's even better. If you just HAVE to have your yellow ink look yellow on a black stock and have the time and energy to do it, you can knock out the area you want yellow and print a white sheet black except for the knockout. Then you can print your yellow and have it look the way you want.