Most are unsightly and can be removed easily, but deep stains or those neglected over a long period tend to require patience and repeated treatments. A combination of methods is often successful. In spite of the best efforts, however, some stains leave their mark. When a stain is removed dirt and other matter on the surface are also removed. This can look like a stain in itself but it usually disappears after a time.
Prevention is always better than cure.
Originally published 1972.