Shine On: New Perspectives on Museum Lighting

Yesterday I attended a workshop organised by the museums association and hosted by Stephen Cannon-Brookes, of UCL Bartlett School of Architecture and lighting consultant. I was there for work, but found it useful for my studies too.

To be honest, it wasn’t all about “New Perspectives” as such, it covered a lot of the the established ground too. But for a non expert like me, that was incredibly useful. It was also an opportunity to showcase the Society for Light and Lighting (SLL)’s Lighting Guide 8: Lighting for Museums and Art Galleries, though at £80 (£72 for the PDF) I won’t be rushing out to buy it. More of an institutional purchase I think. The first speaker, Paul Ruffles, talked us through that guide.

Beautiful objects in beautiful buildings deserve beautiful lighting.

It covers lighting principles, and stuff like visual adaptation, contrast ratio, colour appearance, colour rendering, glare, lighting the interior or display area, day light, electric lighting, access and security and emergency lighting (he explained that one unnamed city museum experienced a spike in consumption they couldn’t explain until they worked out  a security guard afraid of the dark was turning all the lights on at night). The book its just for white box galleries, it also talks about historic interiors; temporary galleries; events and corporate entertaining; the shop and of course the cafe.

He explained that since the pulication of the previous version, LED lighting has become a useful tool in historic interiors, citing an example of Chatsworth’s great stair. Historic interiors need some obvious light sources, standing lamps and the like, but hidden ones -tiny LED spots in to the historic lighting can bring out fascinating details.  However, he warned that when lighting historic places, the LED unit might only cost £28, but the wiring costs hundreds.

His talk was littered with useful tips and anecdotes. Things like keeping track of the spare parts your supplier gives you – I can well believe that when they are needed, no one can remember who put them where. He points out that when you are planning what goes on the floor in your exhibition, you want to think not just about access for wheelchairs, but also access fro whatever cherry-picker or quickup tower you need to replace the lightbulb. Lightbulb replacement is getting less of a need as LED takes over from tungsten, but LED lights can still occasionally fail. And, if you need a five tonne cherry picker to get to the lights, make sure the floor can take five tonnes (and remember it’s turning circle).
Manchester City museum, wall of paintings all lit individually between 50 lux to 150 lux.
material degradation,

Next up was David Saunders of the  International Institute for Conservation talking about The Balancing Act: Light, Conservation, and Access. He started off asking how much light to visitors need to see objects, there is evidently a rule of thumb that the minimum is 50 Lux. But he showed us a  a Durer woodcut and a Turner Watercolour. The Durer needs just a few lux, it’s black and white, and high contrast. Reduced contrast such as in the Turner, increases light needs by factors of 10.

Gary Thomspon’s The Museum Environment was a very influential book, but most of the research that informed it was experiments done in university’s , with populations of students with (being generally younger) better eyesight than the average museum visitor. So a sixty five year ol needs 300 lux for the same performance as a 25 year old at 10 lux. Similarly Colour matching ability peaks in 20s. The ability degrades as you get older. The colour differentiation you can discern as a 20 year old at 10 lux, requires 1000 lux in 75 year old. There are other factors too, which may be less relevant in museum environments, like visual task difficulty (it takes less time to see things in brighter environments).So he points out that a object that we might think needs just 50 lux to see properly might actually need three times as much for older views. Another three times if it’s a low contrast item, which means as much as 500 lux. Ifs it’s a darker object, or a difficult visual task it might need even more.

He went to to explore the history of the research that has led to those squares of blue wool you might have seen dotted around museums and National Trust places. The “blue wool” number has now become an international standard, where 1 fades quickest, and 8 shows the least discernible fading in the same period of time. It turns out that the same amount of damage occurs if you expose something to twice the light for half the time, so, we can think in terms of exposure doses, or lux/hours. The key learning from all this research is to limit the overall exposure to light. He swings by considering the differing levels of damaged caused by different wavelengths of light, mentioning the red/green skylights installed in the roof of the V&A’s Raphael gallery, before concluding that the key learning is to exclude UV radiation.

Then he addresses an interesting question. How long should an object remain unchanged In fact, there’s remarkably little research in this area, and it doesn’t seem that wide-ranging. I drifted off into thinking about an exhibition that explains these issues, and then gives some options asks the visitor how long a selection of items should last “unchanged” (of course what that really means is little or no visible change). What work has been done, David says, broadly concludes a desired lifetime before change of something like 100-150 years.

All this, he concluded, means that when thinking about this, there are very few variables that we have control over. The amount of “acceptable” damage from light is set by the objects desired lifetime, the light dose is set by the object’s sensitivity, and the level of light is set by human need – therefore length (time) of exposure is the only variable we have that’s really under out control as heritage professionals

Then Jo Padfield, conservation scientist at National Gallery, gave us a great talk on all the research work going on there. He started off questioning our arbitrary decisions on lifetime by showing us Paolo Veronese’s The Dream of St Helena, wherein she looks out on a sky that, in his words resembles:

a dull grey afternoon in Glasgow

But closer examination shows it was painted with Smalt, which was Mediterranean blue, and padfield showed us what that might look like. similary, the grey/blue bedsheet of the Rokeby Venus was once royal purple.

he talked a little bit about the change from tungsten bulbs (adjustable in increments of 60, then 30 lux to LEDs to have more control, dimming in 10 lux increments, as well as energy/CO2 reduction. There was an issue with colour quality and consistency of the new LED lamps, so they created an internal website to monitor and research the change to LED lighting. This website is now open to everyone, and some of the audience explained how useful it is.

He also mentioned the Making Colour exhibition in 2014. At the end, he said “we experimented on visitors. Human perception experiments are normally done in the lab with a sample of about 6 people. Our sample was 20,000.” He showed us how unter different bulbs, people saw the same painting differently, in one still life the same fruit could be orange or  yellow,

Jo Beggs, Head of Development for Manchester Museums Partnership, finished the morning with an explaination of where they got funding for improved lighting for the recent, £15 million redevelopment of of the Whitworth museum, especially when the lighting costs went 25% over budget.

There was lots more to talk about after lunch, but that will have to be another post tomorrow.

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