About Sharpness and Cutting Performance
Talking about cutting performance, we come to a common issue in the knife industry – how to measure it. One method is by using the CATRA tester. Due to the high cost of the tester, it's only used by larger knife factories.
The tester measures sharpness by counting the number of sheets of a standardized synthetic paper that can be cut (which is loaded with 5% silica and thus abrasive), from which 2 values are derived:
ICP (initial cutting performance)
Number of papers cut in the first three cycles
Represents the cutting ability of the blade as supplied or after sharpening
TCC (total card cut - sometimes also referred to as CER = cutting edge retention)
Number of papers cut in 60 cycles
Represents the ability of the blade to retain the sharpness over a period of time
Although some conclusions about the cutting performance of a blade can be derived from those values, the test has some weaknesses:
It simulates a slicing cut and thus favors coarse / serrated edges (the best TCC values are produced by knives with serrated edges!)
The blade geometry and surface finish (other than the angle of the cutting edge) have no impact on the values
The values provide less indication of the push-cutting ability of a blade
The values give no indication about the cutting feeling / ease at which the blade glides through food
An instrument that can more accurately measure the sheer sharpness of the cutting edge is the BESS (Brubacher Edge Sharpness Scale) sharpness tester.
This device measures the force in grams of pressure needed to cut through a standardized and certified wire. The lower the value, the sharper the edge. The device is inexpensive and can be used by smaller knife makers as well as knife enthusiasts or even home sharpeners for testing their sharpening skills.
Unfortunately, the BESS value only gives an indication about the sharpness of a new (newly sharpened) blade, but not about the ability of a blade to hold an edge.
Other than CATRA and BESS, there are no commonly used testers or test standards, which means that today there are no test methods available that accurately measure the cutting performance of a knife in its entirety and convert it into objective values.