Block Proofer, System FOGRA, type A: 10 - 10 - 10 - 10 - 10 N/cm2
Pressures of 1.25; 2.5; 5; 10; 20 or 50 N/cm² at choise
In the majority of printing processes, the printed substrate comes off the printing press either stacked (e.g. sheetfed) or rewound (roll to roll processes). It is important to be able to predict the resistance to blocking in the laboratory, prior to actual production printing, in order to avoid the generation of unusable printed matter. It is also used to trouble-shoot and to determine the cause of blocking problems that occur at customer locations. It should be noted that test materials that do not show short term blocking can exhibit blocking after extended periods of time, e.g. weeks or months after printing.
Depending on the printing process, the image can be printed on one side or both sides of the substrate. When the printed matter is collected in a stack or roll, freshly printed ink will be in contact with the reverse, unprinted or freshly printed or semi-dry surface of the substrate, depending to the printing process (offset, gravure, flexo) Stacks and rolls must be able to be subsequently processed such that any interactions between the adjacent layers are eliminated If the adjacent surfaces have (excessive) adhesion or cling, subsequent processing steps can be more difficult or impossible. In the worst case, the printed surfaces cannot be separated without damaging the printed surfaces, rendering the printed matter unusable. Improper storage conditions (e.g. hot humid warehouses) can exacerbate these problems.