We discuss the definition and measurement of knife sharpness. Using a commercial knife sharpness test system we identify a controlled cutting regime that progressively dulls blades, and use this to compare the durability of the edge on a modern knife sharpened with a commercial electrically-driven abrasive-belt knife sharpener with the same blade sharpened manually with a whetstone. Starting at similar sharpness levels we observe that the cold-sharpened edge is significantly more durable.