A few weeks ago, I re-read the Verhoven paper carefully. I noticed something on re-reading that might explain the non-existent stropping results he got with plain leather.

On page 4 of the paper, in the lower right hand corner, he has a table showing the 2-Beta (business edge) of various implements. He lists the 2-Beta edge angle for razors is 15-19 degrees, kitchen knives 20 - 30 degrees, utility and chopping knives 30 - 60 degrees. The straight razor shown in Figure 8 on page 7 measures 17 degrees, smack dab in the middle between 15 and 19 degrees.

But yet - on the machine sharpening with the Tru Hone machine described on page 8, hand sharpening on page 18, and Tormek machine sharpening described on page 25, the 2-Beta blade angle in all tests was between 40 and 49 degrees.

It seems to me that leather stropping only has an effect on the very finest edges. It also seems to me that leather stropping would have a much more noticeable effect on a feathery 17-degree edge than it could ever have on a rugged 40 to 49 degree edge. Could it be this study under-represents razors as an anomaly, in order to concentrate on knife-class edge angles? I mean, the name of the paper is Experiments In Knife Sharpening, after all.