Varnish is a liquid finish applied via the printing press to seal and protect the ink on the printed surface. It is available in gloss, matte, and UV, and is usually matched to the coating of the underlying paper. Varnish is especially good as a cover finish for saddle-stitched products like comic books and magazines.
If you want areas of your cover to really pop, you can use what is called a Spot Gloss, also known as a Spot Varnish or Spot UV.
This is typically applied on top of either a matte varnish or a matte lamination so that the area with the Spot UV will have a high-gloss shine and stand out from the rest of the design.
Lamination is a thin polypropylene film applied to the surface of the paper after printing, via a roller. It provides the ultimate in protection, and is available in both gloss and matte. The sheen and texture of lamination is much more pronounced than varnish — gloss lamination is very shiny, while matte lamination is very smooth. Perfect bound and case bound books should always use some type of lamination for their covers to prevent any damage to the printed surface during the binding process
Lay Flat (Nylon) Lamination is widely used for book covers and other one sided applications because it helps to stop curling.
For products that will be frequently used and will be much more susceptible to scratches and scuffs, applying an aqueous coating will help protect against the signs of everyday wear-and-tear. An aqueous coating also seals the ink on the paper for extra protection against air exposure, which is an important design consideration for collectible items like limited-run comics or exclusive card game expansion packs.
Not all projects require a finish, and if your project is saddle-stitched and doesn’t have heavy ink coverage on the cover, you can choose to skip the finish altogether.