All my knives are made from carbon steel (not Stainless). What does this mean? Carbon knives have a specific metallurgy that gives them strength and edge-holding ability far superior to Stainless Steel. Carbon Steel differs from stainless steel thus requiring a little more care. A carbon steel knife has a tendency to react with highly acidic foods, if the acids are left on the blade. This can cause the steel to turn dark gray to black. To avoid this coloring, immediately after cutting highly acid foods, rinse and wipe the blade, then go back to cutting. Discoloration will not affect blade performance and some people prefer a patina. If water is left on the blade it will rust or cause dark spots. All color changes to the blade can be easily remedied with a green Scotch-Brite pad and a little soap. First, place the flat of the blade on a flat surface to avoid cutting through the sponge or possibly cutting yourself. Next, apply a small quantity of soap along with water on the Scotch-Brite pad. Now scrub the blade. When finished rinse hand-dry.
Most of my pro chefs will let their blades continually patina and over time they turn a slate blue. The oxidation actually helps to protect your knife and will slow the the reaction to acidic foods.
Always hand wash and dry your knife thoroughly. It is gentler on handles and prevents any rust spots on the blades.
Always cut on a board made of wood or soft plastic. Other surfaces, such as marble, metal, glass, and even some hard plastic surfaces can dull the knife’s edges.