I was practicing ( because I'm a newbie) on the sidewalk leading toward my front door of my house with a turbo nozzle on my wand using hot water. When I was cleaning the concrete its like only part of it would get white and the rest seemed like it had a shiny substance on it like sealer or something. My goal was to get it white but the turbo and the heat would not get it totally white. What do you guys think it was. It seemed like a lacquer type stuff (clear) on the concrete. I hope someone can help because it seems like you could run into this anywhere! Thanks!