Stained chimneys are an eyesore and should be cleaned before waterproofing. Stains such as rust, efflorescence (white mineral salts), smoke stains, mortar splash, algae, mold, mildew and more can be cleaned with Brick & Mortar Cleaner from SaverSystems. It can be used full strength on the toughest part of the stain and then diluted for general cleaning. It has no harmful fumes and is safer to use than muriatic acid (which pre-dates WWII). Application is with a pump sprayer and a stiff non-fiber metal brush should be used for cleaning. This chemical can be used on stone, brick and other masonry materials except limestone. Each gallon cleans 50-150 square feet per gallon depending on dilution. Sales brochures available.
From the homeowners point of view their chimney is damaged. It has ugly stains on it and they may think the only way to take care of the problem is to tear it down and replace it or have some of the dirty brick replaced. But they can't afford it. And it's way too difficult for them to tackle. They may not know that there is an alternative. Showing them before and after photos of other chimneys and/or the product brochure will help them to see that there is hope for their chimney. They will also be more likely to consider a waterproofing job, stainless steel chimney cap or chimney top fireplace damper to avoid having this problem again.