over a large flat area it will look splotchy,streaked and hazy.its good for small touch ups.if you don't want to deal with the hassle of epa regs. hot salts is not going to do you any good.state and local clean water agency people have been working with us for years,the batches we do leave allot of salts and acids to prosses,i have been doing this for 15 years,my company has been here for 60 years.soon the only thing left to blue a firearm will be paint.