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 pollu on and climate threaten the preserva on of an qui es. This global problem can be found in our own backyard, New York City, where the Egyp an obelisk is slowly deteriora ng, 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 pollu on.
To compare the condi ons of the obelisks, and inves gate corrosion mechanisms of granite, we studied atmospheric composi on in terms of air‐borne molecules and chemicals, data about weather and precipita on, and the impact of organisms on exposed granite. We inves gated past and present preserva on methods, and evaluated what must be done in the future to best maintain the obelisks. We iden fied which preserva on techniques are most effec ve in protec ng the obelisks, and determined the efficiency of these methods.
London Obelisk A Brief History (6) •The New York and London Egyp an obelisks, known popularly as Cleopatra’s Needles, are twins (2) New York Obelisk •Both were created in the Egyp an city Heliopolis around 1500 BCE and later stood in Alexandria (2) (5) •In 1801 the Egyp an government presented one of these obelisks to the Bri sh (9) •It was finally erected in London in 1878, a er 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 Preserva on(10)(11) Average Rela ve Humidity Per Year •Exposure to acids in humid condi ons 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 excre on London: 20% London of acids, and other materials that transform the 10% •Treated with a weak solu on of Dammar City 0% tough silicate mineral (granite) into so er 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” a er the London 91% 68% vibra ons), especially if the specimen is not kept Rela ve 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 condi ons; this type of Average Precipitation Carbon Dioxide Sulfur Dioxide in the degrada on is extremely likely if the specimen Per Year Emissions per Year Atmosphere •Further restora on 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 be er condi on than its twin in New York. This is an interes ng fact because humid weather condi ons contribute to the corrosion of granite and London has a far more humid environment than New York. Evidence shows that the treatment and restora on bestowed upon the London obelisk has allowed it to maintain a superior condi on compared to its twin. Treatment for the New York obelisk was ini ally delayed and its preserva on has been less intensive. In addi on, large amounts of damage to the New York obelisk occurred while a emp ng to preserve it. To combat mul ple corrosion mechanisms, wax and dis lled water treatments are the most important. Now, granite statues are “leeched” of their salts in dis lled water a er they arrive from the desert, which is a fairly new, but effec ve prac ce. Though it is extremely difficult to combat all the aggregators of deteriora on, more s ll needs to be done to help prevent more damage from occurring. Bibliography 1) “Air Pollu on.”