The pigments in fluorescent inks work by absorbing ultraviolet energy (invisible to the human eye), and transmitting it as longer waves in the visible spectrum.
Cyan, Magenta, and Yellow process inks can be replaced with their fluorescent equivalents for a strange, while at the same time, semi-natural look. Novelty effects in four color process printing can also be achieved by mixing 50% Pantone 803 fluorescent Yellow with 50% process Yellow and 50% Pantone 807 fluorescent Magenta with 50% process Magenta. Alternatively, using one fluorescent ink, usually Yellow or Magenta, in combination with process colors can add impact to the result or help compensate for a poor substrate. This is most often seen in newspaper work where fluorescent Yellow is sometimes used in place of process Yellow.
In addition to the process equivalent fluorescent inks there are some 10 base fluorescent ink colors for print application and which can be used in Hi-Fi image reproduction or as spot/line colors.
Although very bright appearing, fluorescent inks tend to be weak on press and hence should be printed at higher solid ink densities. They often require a double hit, especially on offset coated papers, to bring them up to full potential. They are well suited for gravure printing since that process can lay down a thicker ink film than offset. Note that ink drier additives may be required when running fluorescent inks on coated papers.
Fluorescent pigments, especially the red, are fugitive so exposure to sunlight will rapidly cause fading. Fluorescent inks are not formulated to resist high heat, so they are not suited to stationery that will be run through a laser printer or copier.
Note that the amount of optical brightners used in the substrate to be printed on will have an impact on the final result - see the post HERE for more details.