Ring tear-off method
The ring tear-off method is a variant and historical predecessor of the Du Noüy ring method as it is used today for measuring surface tension or interfacial tension. Instead of repeatedly detecting the maximum force by cyclic elongation and relaxation of the lamella as is usual with modern tensiometers, the lamella is overstretched until it breaks, so that only one value is determined per measurement.
This tear-off procedure originates from mechanical, manual tensiometers, where controlled elongation and relaxation of the lamella is hardly possible. In addition, the maximum force is displayed by means of a drag pointer, whose display value does not decrease again after the force has decreased.
Although it is not technically up to date, the ring tear-off method is still in use today as it is prescribed in older but still valid norms (e.g. ASTM D 971).