The viscosity is measured at 20°C in a Höppler falling ball viscometer. The concentration of a nitrocellulose solution using dried nitrocellulose in acetone, to which 5% water has been added, is standardized such that an apparent viscosity of 400 ± 25 mPa s is obtained in the falling ball viscometer. Sometimes referred to as standard viscosity, the ISO 14446 viscosity is stated as a numerical value identical to the nitrocellulose concentration. If this numerical value is an integer, the grade is a so-called standard grade. Depending on its solubility in ethanol, the numerical value is prefixed with an A (= A grade), M (= AM grade) or E (= E grade).

Using the standard viscosity it is possible to compare nitrocellulose grades supplied by different manufacturers. The standard viscosity of Walsroder Nitrocellulose and Walsroder NC-Chips is shown in the Product Range.