according to the two fundamental blade cross sectional area profiles. Finishing Subsequent to grinding, the blade is polished to various degrees of gloss. The finest finish, used in the most expensive razors, is the mirror finish. Mirror finish is the only finish used if gold leafing is to be part of the decoration of the blade. Satin finish requires less polishing time and therefore is not as expensive to produce. This finish is mostly used with black acid etching. Satin finish can sometimes be applied, as a compromise, to the back of the blade while the mirror finish and gold leafing are applied to the more visible front of the blade. This way the blade will not be as expensive as a fully mirror finished one. Metal plating, using nickel or silver, is also used, but it is not preferred; the plating eventually erodes through use, revealing the underlying metal, which is often of inferior quality. Nickel-plated blades are very difficult to hone repeatedly and are made for mainly aesthetic reasons though lacking functionality. Blade decoration The blade is decorated by engraving or gold leafing depending on the price. Less expensive blades undergo an electrolytic black acid engraving process. For more expensive blades, gold leafing applied by hand is employed, following a traditional process. Sharpening Sharpening is the final stage in the process. At first the blade is sharpened on a grinding wheel. Following that the blade can be honed by holding the blades against the flat side of rotating round stones, or by drawing the blade across stationary flat stones. The cutting edge is finished using a strop. Sharpening is usually not completed during manufacturing, instead being done after purchase. Handle materials and their properties Handle scales are made of various materials, including mother-of-pearl, Bakelite, celluloid, bone, plastic, wood, horn, acrylic, ivory and tortoise shell. Celluloid can spontaneously combust at elevated temperatures. Buffalo horn tends to deform with time and it possesses form memory so it tends to warp. Mother of pearl is a brittle material and can exhibit cracks after some use. Resin impregnated wooden handles are water resistant, do not deform and their weight complements the blade's to provide good overall balance for the razor. Snakewood, Brosimum guianense, is also suitable for long term and intensive use. The mechanical properties of bone make it a good handle material. Handles were once made of elephant ivory, but this