Well, I'm no expert but whenever I strop a hollow there is a scraping sound as the edge moves along the strop. There is also (usually - it's razor and strop-specific) a feeling of resistance (or draw).

You need to use enough pressure to ensure the edge and the spine are in contact with the strop through the whole motion. You should listen for the scrape and feel for the draw, and use no more pressure than is required for those things to occur.

The barber's manual in the archives shows a picture or two of how to hold and flip the razor when stropping. If I remember correctly it looks like they recommend keeping your thumb on the top side of the shank. This may help you keep both the edge and spine on the strop too.

In my experience you are more likely to round the edge by incorrect flipping of the razor at the end of each stroke - make sure the razor never leaves the strop and you flip it on its spine: don't lift the razor's spine off the strop. If you keep your thumb on the top of the shank, this means rolling the razor between thumb and pointer when you flip.

Go slowly and keep the strop taut. This stuff takes time and practice, and if you develop good technique to begin with, practice is more productive. So go slow. And good luck!

James.