The folding and coating breaking properties are particularly important for further processing. These properties are tested using special test procedures. This mainly serves for product development purposes.

Creases and folds, breaking folds

Measuring the residual breaking resistance when breaking folds

In order to obtain the measurement for the residual breaking resistance of paper, the thermal stress in the drying unit and further processing after printing are simulated.

For this, unprinted strips of paper (1) are pre-folded or creased while warm (2) and then folded (3). The subsequent measurement of the remaining tensile strength of the folded test strips (4) yields the measurement of the residual breaking strength (5).

Coating breaking

There are many factors that influence coating breaking. Some of them relate to the way the paper is manufactured, such as composition of material, type and composition of fibres, elasticity, drying process in the coating machine, bond between raw paper and coating layers, to name only the most important.

On the other hand, just as many different factors in the printing and binding plants can influence coating breaking, for example climatic conditions (humidity), correct creasing to allow the paper to expand, fold parallel to direction of paper, etc.

In order to offer the print plant a high level of production security in terms of paper quality, coating breaking is examined. Papers are printed with 100 % black full tone. This is followed by the defined folding of the test strips in parallel with the fibre direction.

Next comes the visual and microscopic evaluation of the bond between the ink on the paper and the outer edge of the fold: The greater the proportion of the black surface ratio, the less coating is broken.

Printing with black full tone	Evaluation