I clean them good with hot water and Dawn dish soap then stick them blade down in a jar of pickled okra or pickled peppers or dill pickles for 6-8 hours. Its rather popular in the Randall community and often referred to as a "pickled" blade. Carbon blades seem to sharpen easier and hold an edge better than stainless, but are susceptible to rust. This "pickled" blade isn't as effective at retarding rust as stainless, but it helps significantly. "User" knives are often exposed to blood, sweat, water, humidity, etc., so this cuts down on the maintenance of the knives. I've heard of other methods of forcing a patina, but this is the one I have had the best results with. Here is a before picture from Arizona Custom Knives where I purchased the used knife and a picture of my knife after the pickle job.