 and let the chemical do the work, you're much better off than trying to sand it out or pressure wash it out. Because think about this. The pressure washer is infusing water. If you're using something like, I don't know, a 3000 PSI pressure washer, which is not abnormal to have in a home, a home garage or something along those lines, and you use a 25 degree tip on that, that's a lot of force.