I have a home that was built from stone in about 1804 and done in a barnwash mortor sytle. Over the years, the stone work has been painted or white washed. I'm sure there are spots where stucco or some other material has been applied in some places. In some areas I can see where there is erosion, sort of a sandy material, on the outside and in the basement. I really don't what that is - if it's mortor or the stones themselves eroding. I'm sure the house would look much better if it were taken back to the stone finish. However, I don't know what to expect from such a process.