Thread: What is this, and is it bad?

It is often referred to as Devil's Spit. Pretty much that is one form of rust in carbon steel. You can never tell how deep it does, so it may be deep pitting when it is demoed or it may be just on the surface. They only way to tell for are is to start sanding.. The stuff near the edge is the only part that effects the shave, the rest is just aesthetics.