For whitening Portland or Painswick stone, pipeclay should answer well, but should be sparingly used - that is. just a smear rubbed on evenly with a wet rag. Or a piece of soft Bath stone (Corsham or Farleigh Down for preference) might be used; it should be rubbed on with a little water and finished with a wet rag. Ordinary hearthstone (Godstone), sold and used for the special purpose of whitening stone, might be tried. Either of the substances mentioned above ought to answer the purpose. The mistake that is generally made is to put on too much of the whitening material, hence it flakes off in places and has generally a rough appearance; whereas if a little of it were carefully and thoroughly rubbed into the stone the result would be satisfactory.