Static and dynamic coefficients of friction are determined with four d
ifferent devices. One testing equipment is based on the principle of t
he inclined plane. The others are ruled by dynamic conditions. Althoug
h design of the instruments concerned and testing parameters are diffe
rent, identical coefficients of friction are obtained. By means of thr
ee dynamic devices the stick-slip behaviour of papers can be character
ized. Due to mechanical interpretation of the stick-slip phenomenon an
error in DIN 6729 concerning the determination of the dynamic coeffic
ient of friction becomes evident.