Assessing the paper brittleness

In order to assess the paper brittleness, fold test is used the most often. There are special devices to perform the fold test (instruments of Schopper, Köhler-Molin, Lhomargy). In this test, a strip of paper is folded back and forth at the same place by 180 degrees until it breaks. The fold indicator is the number of double folds at which the strip of paper breaks.
It is easier to conduct a fold test by folding a corner of a sheet of paper back and forth with fingers. In order to ensure the similarity of folding lines, a template is placed on the sheet corner. A paper with three or less double folds is considered to be brittle.

Fold test always damages the paper!

Corner fold test – measured in the middle of the book, the top right corner of the sheet. Template is placed on the sheet and six folds are made (three double folds), the corner is pulled gently after each double fold. When the paper breaks, it is brittle.