The science behind our cultural heritage
Meeting report by Sally Brown
University of Southampton
ECG Bulletin January 2014
University of Southampton
ECG Bulletin January 2014
Report from an event held at the Institute of Physics, 76 Portland Place, London on 23 October 2013.
When we visit a historic house or art gallery we often take for granted the objects on display, without thinking about how they are preserved or how they change throughout the centuries. These twin talks provided a fascinating evening of interdisciplinary science in trying to understand these issues. A joint event of the IOP’s Environmental Physics Group, the Royal Society of Chemistry’s Environmental Chemistry Group and the IOP London and South East/REMS branches, this successful evening was attended by 50 people. The event was organised by EPG member Brian Davies.
Dr Nigel Blades (National Trust) started off the evening describing the challenge the National Trust faces. With over 1 million objects to display and 150 museums, it can be difficult to control the temperature and humidity of their surrounding environment while making houses accessible to visitors. Nigel explained the importance of relative humidity, that is, the relationship between the moisture content of the air and the content of the material they are trying to protect. Get it wrong, and you could end up with a mouldy painting, cracked lacquer, or warped wood. Get it right, and visitors will not even notice. A relative humidity between 40% and 65% is ideal for keeping artefacts in tip-top condition.
Nigel explained how sensors around a property record temperature and relative humidity, which vary over the course of the year. Staff can adjust the temperature to change relative humidity and thereby help to preserve artefacts. For example, Knole is a large property in Sevenoaks, Kent with fourteen purpose-built panelled rooms designed to display paintings and furniture. Built in an era of no central heating, Knole is well-ventilated and accustomed to cool temperatures. In a cool gallery environment, some environmental problems can be kept at bay, but when moved to a warmer, more humid environment, issues can emerge. For example, in one wooden artefact, larvae had remained dormant for many years, but then suddenly hatched when temperatures rose, leaving the artefact infested with small beetles.
It is not just the artefacts in houses that require preserving, but the buildings themselves. In Dunham Massey, Cheshire, Victorian-designed radiators kept parts of the house warm. The Victorians believed in fresh air, and therefore installed a vent to the outside at the bottom of one radiator mounted to an outside wall. Cold air coming through the vent was warmed by the radiator, providing heat to the room. However, if it was very cold outside, the incoming air could be rather chilly, and this became a problem at Dunham Massey. Unknown to staff, a radiator of this type existed, and in a very cold winter a few years ago, where temperatures reached –19 °C, the incoming air was so cold that the water inside the radiator froze, causing it to burst. Buildings such as this keep National Trust staff busy as they try to preserve them and the cultural heritage they contain within a changing environment.
Joe Padfield (National Gallery) works in a much more controlled environment, but he is a man with a problem. How do you display paintings in an efficient, well-lit environment so they can be seen, when light can potentially damage the paintings, for example causing colours to fade? Unlike the National Trust, the National Gallery only has to consider a few thousand masterpieces, yet these paintings are irreplaceable and of international importance.
In early 2013, newspaper reported that the sunflowers in van Gogh’s famous painting were browner than first painted due to damage from LED lighting. Was this claim true? Joe explained how by taking tiny samples, a few tens of micrometers across, and viewing them under a microscope, conservationists can see how paint changes and fades. In the case of van Gogh’s ‘chrome yellow’ sunflowers, the coating had indeed become browner with time. But were LED lights to blame? Throughout the lecture, the audience learnt about the different parts of the visible spectrum, and how lighting from parts of the spectrum can cause damage. LEDs were not convicted of wrong-doing; rather, it was ambient light throughout the years that caused the sunflowers to fade. You can find out more about spectral power distribution of light and Joe’s research at http://research.ng-london.org.uk/scientific/spd/.
Joe explained that many pigments used in paintings can be affected by light. For example, in one several hundred-year-old painting, there was a lady looking into a dull grey sky. Yet chemical analysis of samples showed that the sky started off bright blue. Thus, if light can change the colour of a painting, it may portray a different meaning. Next time you visit a gallery or historical property, take a careful look at the ambient environment to see how it could influence the artefacts you see—there may be more science going on than you think.
Dr SALLY BROWN
IOP Environmental Physics Group/Department of Engineering and the Environment, University of Southampton
When we visit a historic house or art gallery we often take for granted the objects on display, without thinking about how they are preserved or how they change throughout the centuries. These twin talks provided a fascinating evening of interdisciplinary science in trying to understand these issues. A joint event of the IOP’s Environmental Physics Group, the Royal Society of Chemistry’s Environmental Chemistry Group and the IOP London and South East/REMS branches, this successful evening was attended by 50 people. The event was organised by EPG member Brian Davies.
Dr Nigel Blades (National Trust) started off the evening describing the challenge the National Trust faces. With over 1 million objects to display and 150 museums, it can be difficult to control the temperature and humidity of their surrounding environment while making houses accessible to visitors. Nigel explained the importance of relative humidity, that is, the relationship between the moisture content of the air and the content of the material they are trying to protect. Get it wrong, and you could end up with a mouldy painting, cracked lacquer, or warped wood. Get it right, and visitors will not even notice. A relative humidity between 40% and 65% is ideal for keeping artefacts in tip-top condition.
Nigel explained how sensors around a property record temperature and relative humidity, which vary over the course of the year. Staff can adjust the temperature to change relative humidity and thereby help to preserve artefacts. For example, Knole is a large property in Sevenoaks, Kent with fourteen purpose-built panelled rooms designed to display paintings and furniture. Built in an era of no central heating, Knole is well-ventilated and accustomed to cool temperatures. In a cool gallery environment, some environmental problems can be kept at bay, but when moved to a warmer, more humid environment, issues can emerge. For example, in one wooden artefact, larvae had remained dormant for many years, but then suddenly hatched when temperatures rose, leaving the artefact infested with small beetles.
It is not just the artefacts in houses that require preserving, but the buildings themselves. In Dunham Massey, Cheshire, Victorian-designed radiators kept parts of the house warm. The Victorians believed in fresh air, and therefore installed a vent to the outside at the bottom of one radiator mounted to an outside wall. Cold air coming through the vent was warmed by the radiator, providing heat to the room. However, if it was very cold outside, the incoming air could be rather chilly, and this became a problem at Dunham Massey. Unknown to staff, a radiator of this type existed, and in a very cold winter a few years ago, where temperatures reached –19 °C, the incoming air was so cold that the water inside the radiator froze, causing it to burst. Buildings such as this keep National Trust staff busy as they try to preserve them and the cultural heritage they contain within a changing environment.
Joe Padfield (National Gallery) works in a much more controlled environment, but he is a man with a problem. How do you display paintings in an efficient, well-lit environment so they can be seen, when light can potentially damage the paintings, for example causing colours to fade? Unlike the National Trust, the National Gallery only has to consider a few thousand masterpieces, yet these paintings are irreplaceable and of international importance.
In early 2013, newspaper reported that the sunflowers in van Gogh’s famous painting were browner than first painted due to damage from LED lighting. Was this claim true? Joe explained how by taking tiny samples, a few tens of micrometers across, and viewing them under a microscope, conservationists can see how paint changes and fades. In the case of van Gogh’s ‘chrome yellow’ sunflowers, the coating had indeed become browner with time. But were LED lights to blame? Throughout the lecture, the audience learnt about the different parts of the visible spectrum, and how lighting from parts of the spectrum can cause damage. LEDs were not convicted of wrong-doing; rather, it was ambient light throughout the years that caused the sunflowers to fade. You can find out more about spectral power distribution of light and Joe’s research at http://research.ng-london.org.uk/scientific/spd/.
Joe explained that many pigments used in paintings can be affected by light. For example, in one several hundred-year-old painting, there was a lady looking into a dull grey sky. Yet chemical analysis of samples showed that the sky started off bright blue. Thus, if light can change the colour of a painting, it may portray a different meaning. Next time you visit a gallery or historical property, take a careful look at the ambient environment to see how it could influence the artefacts you see—there may be more science going on than you think.
Dr SALLY BROWN
IOP Environmental Physics Group/Department of Engineering and the Environment, University of Southampton
