Thoroughly clean knife in warm soapy water. Dry well. Room temperature yellow mustard (higher acid % the better). Stiff bristled paint brush. I usually put the mustard in a bowl for "dipping" the brush in too. With brush loaded with mustard use a dotting-swoosh type of motion to coat the entire blade. Let sit & air dry for fifteen minutes (set timer). Wash off with warm soapy water & enjoy your patina. [emoji106] [emoji41]Cheflarge, is there a certain way you applied the mustard to get that pattern?