As a final stage, the paper goes through a finishing process. This can be done in a way that maximizes smoothness. Like ironing, the higher the temperature, the more wrinkles are eliminated. Sometimes coated board will have scratches and streaks caused by particles trapped under the coating blade. The best coating operation helps minimize these problems.
Traditional processes use an air knife coater that follows the surface of the paper.
It's a nice idea, but the end product is only as smooth as the substrate. If the base sheet has bumps this process will simply follow the highs and lows - giving you hills and valleys to print on. Blade knife coating is what you want to look for. It applies an even coating no matter what the underlying surface smoothness might be. The coating formulation itself is another area that can make a huge difference to the printing process.