posted by Suzie Chhouk
Conservation Intern Nicola Crompton in protective gear, cleaning whale bones with ammonia
(c) University of Oxford 2014
(c) University of Oxford 2014
Chemistry does not only play a key role in uncovering the mysteries of our past, but is crucial in preserving the stories artifacts tell. A recent blog entry from the Science Blog of the University of Oxford featured Bethany Palumbo, Conservator for Life Collections in the Oxford University Museum of Natural History. Read the excerpts below to learn how she and her team uses chemistry to restore centuries-old whale bones.
"Cleaning and preserving old bones is an intricate, technical task and each treatment must be tailored to the individual bone. Whale bones are especially challenging, as fatty oils slowly seep out over the years. ...
"Cleaning and preserving old bones is an intricate, technical task and each treatment must be tailored to the individual bone. Whale bones are especially challenging, as fatty oils slowly seep out over the years. ...
"'When we began the project, there were thick layers of oxidised natural oils on many of the bones,' says Beth. 'This unsightly residue not only attracts dust and makes specimens look dirty, but it is also acidic in nature so can damage the bone. When we tested the oils, they had an acidity of pH4 – about the same as most acid rain. The density of the oil varied across the specimens, and the skulls tended to have more oil than other areas. Whales have a hollow area in front of their skulls filled with oil to focus sonar signals which seeps into the bones where it can remain for centuries after they die. Areas of bone, still saturated with this acidic oil, were in some cases crumbling with a gritty texture similar to wet sand.'
"To remove the oily secretions, Bethany and her team brushed solutions of ammonia and purified water onto the bones. Ammonia is an alkaline chemical that works by a process known as saponification that converts fats into soap. Ammonia breaks fat molecules up into their glycerol and fatty acid elements to produce soluble salts and soap scum, which can simply be wiped or vacuumed from the surface. Concentrations of ammonia varied depending on the areas being treated. ... 'There's always a balance to strike with conservation, the treatment method you choose on should never cause more harm than good.'
"As well as damaging the bones, the acidic oil also caused verdigris – the green pigment currently coating the Statue of Liberty – to blossom from the copper wires inside the bones used to support the skeletons. Verdigris can be build up over time when copper reacts with oxygen, and is rapidly accelerated by acids. 'We have now replaced the wires with stainless steel, which is strong and resistant to the environmental conditions of the museum. '
"Ultraviolet sunlight from the glass ceiling destroys collagen in the bones, weakening their structure, and the fluctuating temperatures cause the bones to expand and shrink, weakening joints. Before the roof was repaired, the fluctuating humidity worsened this problem.
"'After a thorough restoration project, I think our whales will have a few good decades more on display. I'm extremely proud of what my team achieved in a short space of time, and hope that visitors will continue to enjoy seeing the whales in the Museum for years to come.'"
Read the whole article on the Oxford Science Blog.
"To remove the oily secretions, Bethany and her team brushed solutions of ammonia and purified water onto the bones. Ammonia is an alkaline chemical that works by a process known as saponification that converts fats into soap. Ammonia breaks fat molecules up into their glycerol and fatty acid elements to produce soluble salts and soap scum, which can simply be wiped or vacuumed from the surface. Concentrations of ammonia varied depending on the areas being treated. ... 'There's always a balance to strike with conservation, the treatment method you choose on should never cause more harm than good.'
"As well as damaging the bones, the acidic oil also caused verdigris – the green pigment currently coating the Statue of Liberty – to blossom from the copper wires inside the bones used to support the skeletons. Verdigris can be build up over time when copper reacts with oxygen, and is rapidly accelerated by acids. 'We have now replaced the wires with stainless steel, which is strong and resistant to the environmental conditions of the museum. '
"Ultraviolet sunlight from the glass ceiling destroys collagen in the bones, weakening their structure, and the fluctuating temperatures cause the bones to expand and shrink, weakening joints. Before the roof was repaired, the fluctuating humidity worsened this problem.
"'After a thorough restoration project, I think our whales will have a few good decades more on display. I'm extremely proud of what my team achieved in a short space of time, and hope that visitors will continue to enjoy seeing the whales in the Museum for years to come.'"
Read the whole article on the Oxford Science Blog.