Thiết bị kiểm tra độ "greying" của giấy in emco IAS

Calender blackening is the optical turbulent appearance of high-smoothed papers, which has a negative influence on the paper quality. The Calender blackening index measures the optical paper inhomogeneity in form of transparent parts in the paper which is caused by the calender.

Due to high local densities, especially at areas of increased basis weight as fiber crossing points, light-scattering interfaces in the paper sheet are reduced in calenders or supercalenders. One says, the fiber collapses. In incident light these transparent areas appear dark. The light is transmitted and partly reflected. This effect of "greying" of calendered paper caused the concept of blackening.

An objective assessment and quantification of the results of calendering can be achieved with the IAS module blackening. The system of Dr. Hermann Praast, Darmstadt, shows the best compliance with the subjective perception.