Sharpening stones are hard and strops are soft. Another soft surface is fine sandpaper on a mousepad. The main difference in stones and strops for me has been taking a razor edge to a shaving sharp razor edge. More recently Iíve been using strops to get better mirror finishes. This is possible with the use of coarser diamond pastes.
The fact that strops are soft means you have to use different techniques. You have to drag the edge instead of push it when stropping. You also shouldnít use too much pressure because it can round off or roll an edge creating a burr. Being soft, the leather will ďwrapĒ around the bevel and edge of a knife blade. This, Iím finding can be used for a convexing result instead of looking at it as a down side of stropping (like I have done). The downside is the leather wrapping around the edge creating a burr. I had already noticed the coarser diamond grits rounding off the line created when changing angles on an edge when using a back bevel and edge bevel. Then there is the line at the top of the back bevel where it meets the ďrest of the bladeĒ.
I recently put a single bevel 28į inclusive edge on my Sage4 (S30V). Using an Edge Pro which creates very flat bevels I had a crisp edge and line at the top of the bevel. After using the coarser grit diamond pastes on strops of cow hide I can see with the naked eye that the crisp line at the top of the bevel is now rounded. Theoretically, rounder bevels will make better slicers than bevels with sharp lines where angles change. Also, there is a convex appearance right on the edge. This should strengthen the edge the same way putting a micro (edge) bevel on a knife with a stone. This knife is a great slicer and the edge is holding up to material like cardboard. Is this because of the slightly convex shape right at the edge? Iím thinking maybe.
This convexing of the bevel with coarser diamond pastes has been mentioned here recently but I havenít realized how much it can be used and controlled to create a different edge than your stones created. Iím sure Iím not the first to ďdiscoverĒ this feature, Iím just realizing it and thought Iíd bring it up for anyone else who hasnít considered it. So, as Iíve used my strops to polish the bevel and add the additional sharpness to the edge I have discovered another use for strops. That is creating slightly convex edges. By adjusting the blade angle you can control how much convexing is being put on the edge or how much is put on the upper portion of the bevel.
I also have horse hide strops. Horse hide is much firmer (harder) than cow hide. Using materials of different hardness is something people might want to play with to find their preference, or preference for different results. You wonít get near the convexing with horse hide because it wonít wrap around the edge as much as the softer cow hide. You can still get the extra sharpness or polish the bevel though.
Any additional info or knowledge about this I welcome. I love to learn from other's experience.