Risk management and light levels
Nicki Smith, National Museum of Australia, 14 May 2010
ERIC ARCHER: We will move next to Nicki Smith from the National Museum of Australia. Nicki is going to be talking about risk management and light levels. Nicki is the deputy manager of the conservation section at the National Museum. She has a background in chemistry and archaeology and studied conservation at the University of Canberra. Nicki has been very involved over the last couple of years in this issue of developing the Museum’s new preventive conservation programs, and particularly the work she has done on lighting guidelines. Nicki, welcome to the program.
NICKI SMITH: Hello everyone. I spoke here last year on much of the same topic. I am delighted to follow Roslyn’s lead and again talk about significance and risk and how we can apply that to lighting guidelines at the National Museum. Firstly, I want to summarise our current lighting guidelines and then give an overview of the year that’s been since the last collections symposium.
One of the primary purposes of a museum is to exhibit, but most of you will be aware that light fades some colours on materials. The fading is cumulative, irreversible and unavoidable for light sensitive materials if they are to be exposed to light. We know the amount of fading is dependent on the specific dye in the substrat, the intensity of the light and the length of exposure, so logically conservators have been recommending display of light sensitive material at low light levels for reduced periods of time.
Our current exhibition lighting guidelines compare an object with blue wool [BW] standards which are known to fade at set rates. The blue wool standards range from one to eight, with one being extremely light sensitive and eight being stable. An example of a one or two would be a photograph, early photographic processes or a blueprint, whereas an eight would be stone, ceramics or glass.
The concept is that the more light sensitive the object, the less time it is on display. By limiting the time per decade, the object retains some ability to be displayed or it has some useful life over at least hundreds of years, possibly even more. For blue wool two and three, we would recommend between 50 and 100 lux and at two years per decade or 20 per cent of the time. This means that it would have four changeovers per exhibition and we take here the life of an exhibition to be about 10 years. Some examples here would be a naturally dyed Maningrida basket or maybe even some low-quality acrylic paintings. For blue wool three and four we would recommend between 50 and 150 lux for 50 per cent of its exposure time, so that means five years per decade. Some examples here would be coloured feathers, many textiles and many paper objects. Above blue wool four, the rates of fading to most controlled light levels such as at museums where the UV is filtered out would be negligible so we would recommend that they can stay on display for the life of the exhibition.
There are two things to note with these current lighting guidelines. If any of you remember last year’s talk when I was talking about evolution of lighting guidelines, I talked about how previous lighting guidelines have banded together blue wool one to blue wool four. That makes a huge generalisation where it means blue wool one objects are overexposed and blue wool four objects are underexposed. We can be confident in separating out between the blue wool ones to the blue wool fours because we now have a micro-fade testing machine - and this is what I have referred to down here, the micro-fading zone. So anything we think is in this range or where we don’t know what the materials might be doing, we test with our micro-fade machine.
Secondly, we no longer specify a set light level such as 50 lux, now we are trying to work with a range of light levels. There is a growing consensus in conservation and understanding - I think Maryanne referred to it this morning as a pseudo science - where to apply science properly or well you need to understand some of the principles behind the assumptions. I think conservation as a whole is beginning to understand that fade rates in lighting are quite complex phenomena and our models and some of our equipment, such as the lux meter, provide assumptions without providing being able to provide exact figures or exact levels of fade rate. We are trying to move to a range of lighting levels that takes into account some of these assumptions and also the fact that we want the object to be viewed. Many people that come into the Museum - part of our demographic is over 40 - statistically once you are over 40 your eyesight ability starts to diminish. For any object that is detailed or dark or large, you need significantly higher levels of light to be able to see it well. One of the things that conservation is coming to terms with is that there is risk in putting objects on display and inherent damage is going to occur, but we do want the public to be able to see objects when they are on display.
This is the micro-fade tester that I was referring to [image shown]. It’s a machine. There are only about eight in the world. It’s a prototype that was developed in North America a few years ago. It has a laser that produces a high amount of light on a very minute pinpoint. We can compare the colour change on the object against the blue wool standards. So in about a 20-minute run we can compare hundreds of years of light exposure. Here is Bruce [Ford] who has done most of the work for us at the Museum, [image shown] where Bruce and I are looking at Azaria Chamberlain’s dress and booties. You can see in the graph [lines showing] the blue wool one fade rate, blue wool two fade rate, blue wool three and blue wool four along the bottom. You can see the little dotted line which I think is Azaria’s booties along here [indicating] and you can see the dress down here below blue wool four, so we would consider that quite stable.
What effect has the micro-fading machine had on our changeover rate here at the Museum? This is a graph of about 200 objects that have been tested over the last 18 months. The benefit of this machine is that it removes the guesswork about where to place an object in the blue wool range. In the past, conservators being conservative have tended to be overly cautious and we have thought, ‘It’s a textile, maybe it’s going to fade, we better stick it in the two years per 10 changeover.’ Now we can test the objects that we are concerned about and say, ‘Well actually, no, it’s a modern synthetic dye. It’s quite stable. We can leave it on for 10 years.’
This graph is a bit of data that we have collected over the last few years [image shown]. You can see that with almost 40 per cent of the objects we have tested their display period that is stayed the same. Our estimation has been relatively justifiable. With six per cent of the objects their time on display has decreased or the number of changeovers has increased. That’s heartening for conservators, because our justification then is we are providing better protection for the collection as it goes on display. Here you can see 66 per cent of the collection has actually increased in display period. That’s fantastic as well. It means that an object that previously might have been in the two years per 10 regime has been moved up so that it can now stay on display for 10 years or the life of the exhibition. That effectively means those objects that would have had four changeovers now don’t need any changeovers, which is a huge release of the burden from staff workloads. Eric [Archer] did a rough calculation with a previous chief financial officer and they came up with a figure of about $1,000 per changeover. Some of you will know that some changeovers will be much easier and cheaper to deliver than that and others will be much more expensive to change over than that, but that’s a rough guide to what we think a changeover might cost.
Having said that, there are two drivers for most of this work - I know there are some assistant directors and acting directors in the audience so often the first priority is to save money, but it’s hard to convince conservators just about saving money. What we actually want to do is provide better care for the collection. By applying risk management principles to collection management, that’s our aim: we want to put lighting in context with other risks that the collection faces. We have to identify that all objects are not equal. Eric talked this morning about history of conservation and I think some of us had the concept when we first studied that all objects were to be treated equal. But in reality times have changed, and we are moving towards a risk-based management model where all objects are not equal. We need to be treating them differently and we need to be assessing each object for the risks that it faces.
Our aim is to add another layer of risk management to our lighting guidelines. The aim is to take our current lighting guidelines based on fade rates and incorporate an estimation of use. Most museums have less than one per cent of their collection on display. A small number of objects are used frequently, a moderate number of objects go on display infrequently and a large number of objects never go on display. We want to include the commonsense idea that, if an object is not going to be on display very often, it can move up one category in the display lighting guidelines.
Those objects that we know or suspect are high use or are highly significant, we would leave at exactly the same levels of exposure and light levels as previously. But those objects that we consider average use or where we consider other risks would take precedence, we want to move them up one step in the lighting guidelines. This one is the same as here more or less [indicating]. We have started to use the word ‘high use’ as synonymous with significance. Significance does not always equate with high use, but it is often a driver for high use.
The category of average use or significance includes other major risks. The common example for an objects conservator is a bark painting or a pukumani pole where handling or changes in fluctuating humidity can cause paint loss, and that is potentially far more significant than a bit of light exposure where red ochres, clay and charcoal are extremely light stable. So here a conservator could be assessing the situation saying, ‘Well, light damage to a bark painting is minimal, but handling, transport, vibration and interventive conservation treatment can have a huge impact on the object. Therefore, we would actually be recommending it stay on display rather than changing it over.’
A similar one is Phar Lap’s heart - dare I mention it? Similarly, the risks to Phar Lap’s heart are in vibration, transport, handling; they are not in light exposure. The significance of Phar Lap’s heart is its size, its physical dimensions. Anything that would impact on the physical dimensions would alter its significance. The fact that it might change slightly from its brownish kind of fixed hue - we may or may not consider that of primary significance.
[Image shown] Here I have put up a slide of a couple of examples where we think things might be high use or moderate or average use. Azaria Chamberlain’s dress and booties - I have been at the Museum 10 years now and this object is always on demand, either on display here or on loan, so this object would be in the high use category. The yellow plastic overpants below - although it’s earmarked for display in our new Landmarks gallery and you can argue that the Snowy mountains hydro scheme is a very important topic and that topic may always be on display or be covered in some form at the National Museum, that particular object may or may not go on display again. There is no history of it being on display in the past. At this stage it would be sitting in the average use category.
To have exhibition lighting guidelines incorporating use rates or significance involves dialogue and discussion between curators and conservators. I guess this is building on what Roslyn was saying: it’s about dialogue, discussion and reaching consensus. Assessments of significance are not new for curators, but we need to build into conservation the idea of significance and risk-based assessments. All objects that come into the National Historical Collection do undergo an assessment of significance. In our discussions to refine our lighting guidelines, we want to be discussing questions like: Is colour of primary significance? Is the object in pristine condition? Will it be frequently requested for display?
Again, the aim here is not to be dogmatic or create concern about allocating about where an object is either high or moderate use or of significance. If there is any feeling of discomfort or uncertainty, we can consider the object high use and we can test it with our micro-fade machine. This will have a slight cost to the Museum but we want to move to is that not only do we have lighting guidelines that are flexible but also that staff here embrace them so that there is some reassurance that we are providing the most appropriate protection to our collection within a risk management framework.
Where are we up to? Over the last year we have had strong support from our curatorial staff about introducing significance into our lighting guidelines. We are at the stage now where we are trying to work through in reality how feasible is it for a curator to allocate a level of significance or use every single time an object is selected for display. This will not be quick, considering the object list for Landmarks alone is around 1300 objects. Conservators then need to be involved with the discussion and assess how the risk of lighting relates to other risks associated with the object. But re-assessing significance or use each time an object is selected for display allows for significance and use to change over time, which I am sure you are aware is highly possible. We will also need to modify our collection database to incorporate and track the decisions made around each object. However, the benefit is obvious to this work: There is a small amount of effort required at the beginning but the pay-off to the Museum as a whole is quite considerable. Not only does it save us money but also it allows us to prioritise our workloads under a more systematic risk management framework.
[Image shown] Here is a bit of an estimation about the number of changeovers for the lifetime of a gallery, which I have taken is about 10 years, and I have assumed about 100 objects in the gallery. Some of you will know that GFA [Gallery of First Australians] is sitting around 1000, Landmarks, the current gallery being developed is more than 1000 objects, and our Australian Journeys gallery has a bit less than 1000 objects. These figures are not to be taken as representative of a gallery; they are just to give you an idea of how changeovers might change if we applied significance or use rate lighting guidelines.
Here we have our blue wool equivalent and we have the number of objects that we are guesstimating might be in each blue wool equivalent. We have estimated five per cent are in the extremely fugitive light sensitive area. This is a bit of an overestimation but it allows for some loans - in the past we have loans we have had to change over every three months. We have guesstimated 35 per cent sitting in the two to three blue wool range, 30 per cent in the three to four range, and 30 per cent in the lifetime of an exhibition. Time on display in years would be less than two years, two years, five years and 10 years. This means the number of objects that would actually be sitting in that blue wool category would be 50, 350, 300 and 300. The number of changeovers per object would be more than four, four, one and zero. So the total number of changeovers ends up with about 1900 for that gallery over a 10-year period. That is with our current lighting guidelines using the micro-fade machine to make the best estimate of light sensitivity.
If we apply our use-based or significance-based guidelines, again I have just plucked a figure out of the air - 10 per cent are high use - you can see exactly the same. We have our blue wool equivalent, we have our per cent of objects per blue wool category, time on display, number of objects and then we start to split. Because blue wool one to two are so light sensitive we haven’t recommended leaving any of them on display, we have maintained the status quo or we would recommend coming off display at the less than two-year period. We are assuming 10 per cent of our blue wool two to threes are high significance and the remainder are average. And so it goes on. Again, we applied a number of changeovers per object. The total number of changeovers comes down to about 685 compared to 1900 previously. That is with a 10 per cent high use rate. If you want to be more conservative and say you consider 20 per cent of objects in your gallery are high use, your changeovers are still going to be reduced by at least half.
Hopefully by this time next year - I don’t know if Guy [Hansen] will let me come back to the collections symposium next year - I will be up here saying, ‘Yes, we have implemented risk-based exhibition lighting guidelines; yes, our changeover program has decreased; yes, we are still adequately protecting our most light sensitive material; and yes, we are prioritising our resources to where is the most benefit to the collection.’ I would like to acknowledge some of the objects we have tested [image shown], Bruce Ford for all his work in the light fading conservation section, and staff of the curatorial section that have been involved with these discussions. Thank you.
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Date published: 12 July 2010