To remove rust stains from Brick, Concrete, or Granite surfaces:
- Make a poultice from 7 parts lime-free glycerine, 1 part sodium citrate (available from drug stores), 6 parts lukewarm water, and enough powdered calcium carbonate (chalk) to create a thick paste.
- Apply this paste to the stain and allow to harden.
- Remove with a wooden scraper and repeat if necessary.
- Wash area thoroughly with clear water and let dry.