Blue #1 steel has several different names, which can be confusing. It is called Aogami #1 (aogami translates to blue) and it also can be called blue paper #1. The steel has been wrapped in blue-colored paper for decades and this is why it's called blue. Hitachi high carbon steel is very pure and was specifically developed for tools and knives. Blue #1 is easy to sharpen, takes a very fine edge, and holds it for a long time.