 any kind of mold, mildew, algae, lichen growing on that deck surface. Then the other thing that you could do is you could use a product called Spray and Forget. Now, what Spray and Forget does is it reacts with the sunlight to also kill whatever growth is on that deck, but it doesn't happen instantly. So I would put it on as a last step because if you have a heavy coat right now, you're going to wait all summer for it to