Bob Tate Blades are made of 52/100 bearing steel. They are not stainless. They will develop a patina over time. If left in water or wet, they will rust. When using them to cut highly acidic foods such as tomatoes, lemons or red meat, be sure to rinse them periodically to prevent them from turning black. As the patina develops the knife won't stain as easily. Simply hand wash and dry your knife when your done using it. We think the extra care is worth it, because of the superior nature of carbon steel. The picture shows a nice new shiny knife above an older knife with a nicely developed patina.