The nip width is a function of physical roller characteristics and impression pressure. Nip width must be measured and checked each time a new cylinder is loaded. Nip width can be checked by a variety of methods. One is the grease and paper method. Grease, mixed with carbon black, is spread on the rubber impression roller.
Paper is inserted between the impression roll and the cylinder, and the impression roll is lowered.
When the two contact, the grease leaves a mark on the paper that can be measured. These methods are more convenient than paper and grease and are just as effective. Impression Roll Construction. Roller base construction is similar to cylinder base designs. Most are made of durable steel cores with a soft covering.