I found some interesting (I think) notes on early efforts at stone preservation: Thomas Egleston in 1860 reported success in the use of boiled linseed oil, brush-applied in the summer when the stone was very hot. Alexis Julien used the same technique followed by a weak solution of hartshorn (ammonia) in warm water on 2 Manhattan residences and a Brooklyn church in 1884. He found that the treatment would last 4 or 5 years until it became grayish, partially disappeared & required removal. The gate houses of the Croton (now Central Park) Reservoir underwent a process of Castile soap followed by alum solution in 1863. That same year, J.C. Coombe was granted a patent for masonry preservation involving treatment with alkaline salts followed by flourosilicic acid. In the 1880's, Egleston became interested in formulations of paraffin, oil and sulfur (omitting the sulfur in the case of sandstones) and recommended (but did not carry out) such a treatment for Trinity Church in the summer of 1884. Robert Caffal was issued a patent in 1880 for a "formulation for waterproofing and preserving building materials" composed of paraffin, creosote and turpentine. Dr Caffal used a hot wax method of treatment on The Obelisk (Cleopatra's Needle) in Central Park in 1885 (it had deteriorated rapidly since it's arrival from Egypt in 1880). Caffall was living in Phila in 1883 and treated some buildings there and in New York with "a mixture of paraffine and carbolic acid." He reported heating the stone with a flat-sided stove (curved areas and moldings being heated by means of a blast flame from India-rubber bags of illuminating gas). In Sweet's Catalogue of 1906 appears a two step Farnham Patent method sold by the National Waterproofing and Cleaning Company, using a hot paraffin application followed by sandblasting to remove excess material. The advertisement reported the treatment having been used at the US Post Office in Minneapolis, the State House in Boston, the New Government Printing Office in Washington DC, the Studebaker Memorial Church in South Bend Indiana, and on buildings of the US Naval Academy at Anapolis. London's Cleopatra's Needle was treated with the Caffall process in 1879, 1895 and 1911, and the same process was used at Trinity Church in 1926. In 1949, "tarry deposits" were removed from the Needle with an emulsion of carbon tetrachloride, benzene, and an aqueous detergent; and hot wax was re-applied. Central Park's Needle was re-treated in 1913 with China wood oil. The article, Chemical Treatments for Masonry: An American History by Norman Weiss goes on to describe the manufacturing of vinyl resins in the mid-to-late 1920's, and it's use in the treatment in 1935 of the Tumacacori National Monument in Arizona.; the 21 colorless products appearing in Sweet's File in 1942; and the manufactuing of silicone resins in 1943 by the new corporation, Dow Corning. I have 2 pages of the article (don't know how long it was, originally) that was published (not tool long ago) by the APT. If any BP'ers are interested, I could probably figure out how to scan it into an attachment. Wishing all a good summer John Mascaro