I was talking with one of my old friends who was a young man during World War II. I was telling him about how stropping a disposable razor against your forearm definitely works and makes the blade last much longer and he told me this story. During the war, steel was in short supply so they had to make things like double edge blades for their safety razors last. He said what they did was take a small juice glass and put the blade in the glass. Then they would press down on the thin blade to give it a slight curve and rubbed it back and forth about ten times inside the glass. He said it worked like a charm.