Inspection can occur during or after the manufacturing or printing process.
The rub test comprises rubbing a sample sheet across a portion of a recently printed plastic-coated sheet under controlled conditions to determine whether the printed ink was properly applied and dried. With perfect printing, no ink should be transferred to the sample sheet. The image below illustrates an example where a visible amount of ink was transferred to the sample sheet. One objective of image analysis is to quantify which ink and the amount of ink in a three-color printing operation was transferred to the sample sheet. Color data from a sample sheet shown above and from an unused sample sheet were collected.