White steel is the purest of the Carbon steels. The ingredients are Iron and Carbon (up to 2.7%). This is the easiest steel to sharpen and is capable of achieving the most perfect mirror finished edge. This steel has the ability of being forged to incredible hardness which translates to exceptional edge retention. Why do you think sword makers love this steel? Special care must be taken with Shiro-ko knives as they are the most reactive, however after a nice strong patina has formed on the blade they are less likely to rust. Patina is your friend.