Hi - as per title I have to clean a chimney tomorrow however not sure how and what to use to clean it .... All around has a WHITE STUFF on bricks which looks similar to salt - very hard and in some places 1/4 of inch think . I tried a turbo nozzle at about 2800 psi and it doesn't help - nothing at all - the customer said that many years ago it was the chimney of an oil burner ?! now not in use .. I forgot to take a photo .... Tomorrow I have to finish to clean his roof and it will brilliant if I can leave the chimney clean too . may be somehow to use a sander ?! : ) or a chisel however there are few damaged bricks and I assume somebody already tried ... any ideas ?!