One of the greatest advantages of UV ink is its compatibility with a wide variety of substrates. Unlike solvent or water-based inks that react with the surface or get absorbed by the coating, UV ink sits on the surface and bonds to it just like an adhesive. A number of factors, including the finish and composition of the surface and the amount of ink being used, can affect the strength of this bonding.
In some cases, the more ink you use, the better the adhesion, since the contact area between the ink and the surface is bigger. We have found that applying a clear undercoat can significantly improve ink adhesion on certain substrates, such as aluminum and polyurethane. So, the next time you are up against an ink adhesion issue, try printing a layer of matte varnish first and then printing the color image on top. If this works, it may still be a better proposition than applying primers manually.