Catch a Falling Obelisk Mark Barahman, Dan Feldman, Jeremy Lyons, & Michelle Plastrik MHC 3: Science and Technology of New York City, Fall 2009 Professor: Sophia Perdikaris Technical Advisor: Gregory Donovan Abstract The future of the ancient world is at a crossroads, for polluon and climate threaten the preservaon of anquies. This global problem can be found in our own backyard, New York City, where the Egypan obelisk is slowly deteriorang, as is its twin in London. Our project sheds light on the dangers facing monumental works of art and the technology being used to stop the ravages of me and polluon. To compare the condions of the obelisks, and invesgate corrosion mechanisms of granite, we studied atmospheric composion in terms of air‐borne molecules and chemicals, data about weather and precipitaon, and the impact of organisms on exposed granite. We invesgated past and present preservaon methods, and evaluated what must be done in the future to best maintain the obelisks. We idenfied which preservaon techniques are most effecve in protecng the obelisks, and determined the efficiency of these methods. London Obelisk A Brief History (6) •The New York and London Egypan obelisks, known popularly as Cleopatra’s Needles, are twins (2) New York Obelisk •Both were created in the Egypan city Heliopolis around 1500 BCE and later stood in Alexandria (2) (5) •In 1801 the Egypan government presented one of these obelisks to the Brish (9) •It was finally erected in London in 1878, aer a hazardous journey by sea (2) •Later in the 19th century Egypt gave the other obelisk to New York • It was erected in 1881 (2) Results Our research yielded results in three main categories: Atmospheric Data(1)(3)(4)(7)(8) Corrosion Mechanisms(12‐20) Methods of Preservaon(10)(11) Average Relave Humidity Per Year •Exposure to acids in humid condions New York: 100% •Long exposure to water (downpours, snow) while 90% •Treated with molten paraffin three mes 80% being infested with crystallizing salts derived from (1884, 1893, 1914) 70% 60% the atmosphere 50% Percentage 40% • 30% Growth of biological organisms and their excreon London: 20% London of acids, and other materials that transform the 10% •Treated with a weak soluon of Dammar City 0% tough silicate mineral (granite) into soer mineral New York resin and wax dissolved in petroleum (1879) Morning (Gypsum), which flakes off Time of Day Evening Morning Evening •Similarly treated with paraffin or ceresin New York 71% 54% •Exposure to stress (such as Subway and traffic dissolved in a “suitable vehicle” aer the London 91% 68% vibraons), especially if the specimen is not kept Relave humidity: The amount of water vapor in the air as stone was cleaned (1895, 1911) compared to the percent of the amount of water vapor it under some kind of pressure (leaning on would take to saturate the air (expressed as a percentage). something, enclosed by a box, etc.), most •Washed with pressured water (1932) prominently under warm condions; this type of Average Precipitation Carbon Dioxide Sulfur Dioxide in the degradaon is extremely likely if the specimen Per Year Emissions per Year Atmosphere •Further restoraon work was done (2005) New York 46.7 in 58.3 million Kt 26 micrograms/m3 suffered prior cracking (such as cracking during London 29.7 in 44.3 million Kt 25 micrograms/m3 transport) Conclusions Currently, the London obelisk is in much beer condion than its twin in New York. This is an interesng fact because humid weather condions contribute to the corrosion of granite and London has a far more humid environment than New York. Evidence shows that the treatment and restoraon bestowed upon the London obelisk has allowed it to maintain a superior condion compared to its twin. Treatment for the New York obelisk was inially delayed and its preservaon has been less intensive. In addion, large amounts of damage to the New York obelisk occurred while aempng to preserve it. To combat mulple corrosion mechanisms, wax and dislled water treatments are the most important. Now, granite statues are “leeched” of their salts in dislled water aer they arrive from the desert, which is a fairly new, but effecve pracce. Though it is extremely difficult to combat all the aggregators of deterioraon, more sll needs to be done to help prevent more damage from occurring. 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