Hi Folks, Sorry to take so long to get back to you all on this but I have been away. I finally received the information from the Association for Gravestone Studies, both a Primer on Graveyard Preservation and advise directed at my specific problem, lichen and moss. To summarize: Start the cleaning process with fresh water and a soft scrub brush. Before scrubbing wet the stone thoroughly, emphasis VERY THOROUGHLY. If it can be reached with a water hose play a heavy mist on the stone for a good five minutes before scrubbing. Begin at the bottom!!! If you are not near a continuous water source but have a common garden sprayer tank fill it with water (usually about two gallons) and spray the stone. Refill and do it again. Get the stone very wet. Scrub away. You will find it will take several scrub and rinse cycles to soften the lichen and moss. A craft stick (like a popsickle stick) is useful to scrape the affected area. Keep the working area wet!!! Should the result of the above process and material not be satisfactory mix 1 cup of HTH (a product name for calcium hypochlorite - the same stuff used in swimming pools-it is a biocide) into a gallon of hot water to get the granular HTH into solution. Go through the same process as above being careful to rinse the stone thoroughly with fresh water following the application of HTH solution. This stuff smells like bleach but it is not bleach! DO NOT USE BLEACH. DO NOT USE OTHER COMMON CLEANERS. Procedures to Avoid: Avoid Acidic Cleaners on marble or limestone Avoid sandblasting gravestones Avoid high-pressure spraying Do not attempt to clean any stone that is unstable Never use wire brushes or any metal instrument in cleaning stone Do not clean stones often Avoid treating stones with "protective" coatings that are impermeable to water vapor Tools for Stone Cleaning: Plastic pails Goggles Rubber gloves Tampico (natural bristle) or plastic scrub brushes Toothbrushes Smooth wooden sticks Q-Tips Spray bottles Water source Energy (elbow grease) For a Soapstone Tombstone use water only. For Slate and Sandstone use water or non-ionic detergent and water For Marble and Limestone water only or non-ionic detergent such as Photo-Flo or Triton-S 100 or Igepal and water. Use 1 ounce to 5 gallons of water Use Vulpec and water - 1 part Vulpec to 2-4 parts water. Household ammonia - use 1 cup to 4 cups water Use Calcium hypochlorite - use only to remove biological growth - available as swimmingpool disinfectants - must be dissolved in warm water The book "A Graveyard Preservation Primer" by Lynette Strangstad is available from the Association for Gravestone Studies by calling (413) 772-0836 or writing 278 Main Street, Suite 207, Greenfield, MA 01301. Including shipping the book is $21.00 I will not be able to get back to this stone for a bit so cannot give you a report of success but it sounds like this should do the job. If it does not I am advised to get back to them for poulticing instructions. Happy Tombstone scrubbing everyone!! Marion Bale