of thirty degrees to the skin and in a direction perpendicular to the edge; an incision requires the movement of the blade to be sideways or in a direction parallel to the edge. These circumstances are always avoided by the shaver, who always shaves in a direction perpendicular to the cutting edge of the blade. To be most effective, a straight razor must be kept extremely sharp. The edge is delicate, and inexpert use may bend or fold over the razor's edge. To unfold and straighten the microscopic sharp edge, one must strop the blade on leather periodically. A 1979 comparative study of straight and electric razors, performed by Dutch researchers, found that straight razors shave hair approximately 2/1000 in. (0.05mm) shorter than electrics. To sharpen or finish the blade using a suspended strop, the razor is pushed toward the suspension ring while both the back and the cutting edge lie flat on the strop and with the back of the blade. No pressure should be applied on the cutting edge. A strop may be two sided with leather on one side and cloth on the other side. The cloth is used for blade alignment and sharpening. The leather is for finishing. The stropping process involves sliding the razor blade flat on the strop; upon reaching the end of the cloth or leather near the suspension ring, the blade is turned about its back (clockwise for a right-handed barber; counter-clockwise for a left-handed one) until the cutting edge touches the strop. It is then pulled toward the rectangular handle of the strop with back and cutting edge flat on the strop as before. The blade is moved in a slightly diagonal direction so to give every point of the edge a chance to touch the strop, without applying too much pressure. This process aligns the cutting edge properly with the back of the blade, avoiding "bumps" on the cutting edge. Rotating the blade on the strop about the cutting edge can damage it because such use will impact the micro-alignment of the edge. Depending on use and condition, the blade can be sharpened occasionally by using a razor hone. Strops prepared with pastes containing fine grit are also used for honing but are not recommended for the inexperienced user, as they can easily rake off the edge if they apply the wrong amount or exert too much pressure. Some strops