I was thinking that the Sand Blaster would be useful for cleaning limited areas of brick that has algal or mold growth on it (basically kill it first, let dry, then sand blast the surface). They use soda ash blasters to clean mold from crawl spaces. Thinking low cost and useful..... just don't know if they have enough power/pressure. I googled them and there are quite a few different models. I assume that you need a compressor to run them. Hickory, when you use the diamond stones, use very light downward pressure when sharpening a knife. If you press too hard, you knock off the diamonds.