"All models are wrong but some are useful."

The usefulness of any test boils down to the sources of variability, their relative magnitudes, and which ones can be controlled.

There are many sources of variability in a straight razor shave - how well the razor is stropped, how good the beard prep is, how sharp the edge is, how experienced the user is, how the beard grows etc etc.

This is why people tell you that if you want to use any test (HHT or otherwise), it needs to be calibrated using many test -> shave -> evaluate iterations under the many and varied shaving situations you encounter (difference razors, hones, soaps, increased ability through time, etc.) At least when you simply focus on yourself, you can control one of the biggest sources of variability - person to person variation. The longer you have been at it the better the test will be for you. Moreover, the more things you have tried (hones, creams, strops, razors) the more generalised the test will be for you as well.

It has been brought up many times in the past, but the idea of using a standardised HHT material (like fishing line or similar) in an attempt to make the test more universal and repeatable is a good thought, but ignores the basic fact that the main source of variability in these tests is not how they are done and with what material, but rather in what the test means for individual's shaves - in other words, individual to individual variation swamps the variation attributable to the mechanics of the test. It always has and it always will.

James.