Why are Metallic inks so difficult to laminate or UV coat over?

Two Primary factors influence the manner in which a metallic ink accepts a laminate.

1. The lubricant added in the manufacturing process of the inks can migrate to the surface as the ink dries. During the lamination process the adhesive is unable to bond to the lubricant on the surface and this results in poor adhesion.

2. More prevalent is the poor cohesive binding of the metal particles in the ink. Consequently, when the ink is UV coated or laminated, adhesion only occurs on the surface or top layer of the metal particles in the ink.
Since the layers of metal are not bound tightly together. Laminated inks, especially where metallic ink bleeds over the trim, will delaminate when subjected to stress. There are metallic inks that can be coated or laminated. Unfortunately, due to compromises in the manufacturing process they do not have the same degree of luster and are sometimes referred to as "fake" matallics.