The ink-jet decoration - that has replaced traditional decoration systems - has removed several problems bringing out, however, new and more complex critical issues. The new scenario has forced a different attention to all those applications that occur along the glazing line both before and after the digital printing process. In particular, the different nature of the solvent-based inks, with respect to all the water-based applications of the glazing line (engobes, glazes, grits, etc.), often leads to repellency phenomena that can compromise the proper printing process. In addition, the glaze applied as a final protection (on the ink), when not accurately mixed with proper chemicals, may lead to excessive or low drainage, or even to phenomena of inhomogeneous ink's absorption. What kind of action must be taken in all these cases? What are the PRIMERS usually involved and how do they work?