It looks like a beautiful example of ash to me! Perfectly harmless. You can choose to leave it be, or remove it. When I want to get rid of it because it ruins the look of my design, I use a dash of warm water and scrub it off with panty hose. Some people steam it off. It's totally up to you if/how you want to deal with it. If you leave it be, it'll be gone in the first couple uses.