* Alignment: The main purpose isn't actually to "sharpen" the blade by removing significant metal. Instead, stropping aligns the edge of the blade. Shaving can cause the very fine cutting edge of the razor to become slightly bent or burred at a microscopic level. Stropping gently realigns these tiny imperfections, bringing the edge back to its optimal, straight configuration. This makes the blade feel sharper and perform better.
* Polishing: The leather, especially when treated with honing compounds (though this is less common for daily stropping), can also polish the very edge of the blade. This smooths out any minute irregularities and helps create a smoother, cleaner cut.
* Removing Residue: Stropping helps to remove any microscopic residue (soap, hair, skin cells) that may be clinging to the blade's edge. A clean edge cuts more effectively and is less prone to dragging or catching.
* Maintaining Sharpness: By regularly stropping before each shave, barbers can maintain the razor's sharpness for a much longer period. This reduces the need for more aggressive sharpening methods (like using a honing stone) which remove more metal and can shorten the life of the razor.
In short, stropping is more about refining and maintaining the edge of a razor than actually sharpening it from scratch. It's a crucial part of a barber's routine to ensure a smooth, comfortable shave.