disaster!

On my return to the Island in 2003, I noticed that the stones looked too clean. When I enquired, I discovered that the day before I arrived, they had been washed with Hydrochloric Acid.
I immediately made a poultice of limewash, and coated all the cleaned stones with a layer of lime, and then wrapped the stones in plastic.
The lime will eventually weather off, after about 15 years. after this time, hopefully the damaged stone surfaces will have had time to stabilize, and the lime would hopefully fill any micro fissures opened by the acid. About 50 stones had to be treated i this way. Needless to say, I was not very happy. At all. No acid rain in Barbados had reserved these stones to the degree that many looked like they had been carved yesterday. And then, they get washed with acid!
I discovered that the best way to clean them, was to administer a very dilute layer of lime wash. ( almost just lime water). This killed the algae that grew on the stones, and the winter rains washed the thin later away within a season. Quick, easy, and economical. Also, not harmful to the stones.