Protective Coating
A clear spray, laminate or varnish applied over a print to guard against ultraviolet light, moisture and abrasion.
In depth
Coatings extend display life and allow prints to be shown unglazed, which some galleries prefer for large work. They also change the surface: a matte spray lowers Dmax slightly, a gloss laminate raises it. Application must be even and thin, since a heavy or patchy coat is more damaging than none.
Examples in practice
A large canvas print is sprayed with a matte ultraviolet varnish so it can hang unframed without fading.