UV Printing vs Conventional Printing

UV Printing was almost unheard of until recently.  So what's the difference between UV and Conventional printing, you ask.
The printing process is almost exactly the same for both conventional and UV printing; the difference comes in the inks and the drying process associated with those inks.

Conventional offset printing uses solvent inks – which are not the greenest option – because they evaporate into the air, releasing VOC's.  They often require additional spray powders to aid in drying.  Because they are absorbed into the paper, colors can become diluted and less bright. Depending on the papers character and weight, drying can add days to each job. Conventional inks must be absorbed by the substrate they are printed on therefore, you can not use them on materials like plastic, foil, or acrylics.