Ultraviolet (UV) Coating
Ultraviolet coating has come a long way since its inception. Originally, UV coating needed to be applied so thickly that only silk-screening could adequately flood the sheet before drying. Today, there are converted litho presses and stand-alone dedicated UV coaters that apply and dry the sheets at normal press speeds.
UV coating is so named because the liquid carries photoinitiators that dissolve when the sheet is passed under an array of UV lights, dispersing a drying agent that works virtually instantaneously. UV can produce a very high gloss but is also available in matte and satin finishes from many printers.
Early UV coating tended to crack if the sheet was folded (especially along the spine of saddle stitch books), but modern coatings have minimized this problem. Scuff resistance can be quite high, depending on the type of UV coating used and the way that it’s applied. Again, I’d ask for samples.
I’ve heard people say that UV coating reduces ink fading under certain lighting conditions (like sunlight), but I’ve never been able to confirm this.