Museums USA

Revising the gold standard of environmental control

There is an impasse preventing the world’s art museums from adopting less stringent standards

Throughout their history, art museums have spawned and fostered a subculture indifferent to developments in the world at large. Our ocean liner-like art galleries are slow to change course even in the face of evidence demanding it. A critical illustration of this habit is the rigid formula arrived at long ago that prescribes the set points of relative humidity and temperature in our museums.

It remains an unshakable conviction for most conservators and administrators that unless a museum can guarantee lenders that its interior climate is 70 degrees Fahrenheit (21 degrees celsius) and 50 per cent relative humidity (with an allowance for minor fluctuations), it has no business asking for loans, and cannot be trusted with its own collection. That conviction informs many facets of a museum’s operations beyond the cost, including how art is borrowed, lent, shipped, installed and stored.

There are three considerations involved in prescribing the upper and lower limits of relative humidity, or RH. The first is the RH set point—the most generally accepted percentage of relative humidity. The second is the allowable fluctuation—the extent to which higher or lower percentages are considered acceptable. And the third is the seasonal adjustment—the extent to which the set point is permitted to change based on the impact of higher and lower exterior temperature and humidity.

The identification of fixed set points was explored in the early 20th century in select US museums, but the defining events surrounded emergency responses to the aerial bombardment of the UK in the first and second world wars. Temporary storage of the British Museum’s collections during the first world war in underground rail tunnels was followed by 1930s studies of the effects of humidity on art, but with mixed evidence about the specific effects of different ranges. With the advent of the second world war, works from several galleries and museums were stored in environmentally stable slate quarry caves in Wales, with no discernable changes in their condition. In the aftermath of the war, the approximate temperature/humidity ratios of the caves became the gold standard for climate control in museums.

By 1960, scientific inquiry had bolstered the legitimacy of these set points, as articulated in studies such as H.J. Plenderleith and P. Philippot’s “Climatology and Conservation in Museums” of 1960. Like others preceding it in Britain, this particular study concluded that changing relative humidity was a key culprit for the degradation of works of art, but did not advance our knowledge of specific ranges that were better or worse for specific media under specific circumstances.

These earlier assumptions were challenged 16 years ago. In 1994, the Smithsonian Institution’s Conservation Analytical Laboratory issued revised guidelines allowing for as much as 15 per cent fluctuation in relative humidity (35 per cent to 65 per cent) and fluctuations by as much as ten degrees Celsius (52 degrees Fahrenheit to 88 degrees Fahrenheit), regardless of the materials from which objects were made. As research progressed others also came to the conclusion “most museum objects can tolerate, without mechanical damage, larger fluctuations than previously thought” (David Erhardt and Marion Mecklenburg, “Relative Humidity Reconsidered” in Preventive Conservation: Practice, Theory and Research, 1994).

No one would argue that environmental fluctuations should be allowed to occur unchecked within a museum. But the question is this: given the scientific evidence that works of art made from multiple categories of media have not been shown to sustain damage from the incremental fluctuation of relative humidity to a greater extent than currently prescribed, is it time to arrive at an international consensus on loosening environmental strictures?

Some of today’s protagonists moving this discussion towards new protocols include Nicholas Serota, the director of the Tate, along with members of the scientific community, including the International Institute for Conservation (IIC). In May 2010, the IIC and the American Institute for Conservation will be co-sponsoring a roundtable session in its series “Dialogues for a New Century” to review the latest findings, and address the impasse still preventing the world’s art museums from adopting a less stringent standard (the discussion follows a September 2008 summit in London, “Climate Change and Museum Collections”). Many of us hope that a new protocol tolerating greater elasticity may be the outcome, allowing for significant cost savings in energy bills, a reduced impact on carbon emissions, and a more reasonable approach to sharing art treasures with institutions that have heretofore been penalised for failing to meet the rigid standards that have prevailed since the second world war.

The writer is the director and chief executive of the Indianapolis Museum of Art

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16 Dec 10
8:43 CET


Until a more current set of standards is agreed upon, and whether seasonal fluctuation is permissible, it is important that Conservators and Directors be able to operate their climate control systems with reliability and accuracy, and at the least possible operating expense. I invite you to visit for further information, and if you like, phone calls are certainly welcome to answer your questions.

1 Nov 10
13:44 CET


It seems restoration of artifacts is the focus of concern. Has it crossed the minds of officials that the RH control within museums helps prevent the breakdown of the paints and other mediums used in earlier times containing heavy metals like lead, mercury, cadmium, etc? RH controls would prevent airborne releases of these toxins within the museums themselves. A further question is when the EPA spends millions of dollars to carefully remove paints containing these heavy metals from schools, libraries, office buildings and dwellings it does nothing to address these contaminants within our museums?

28 Oct 10
16:0 CET


It is a pity when financial considerations completely screen the importance of saving art (cultural) treasures for future generations. Those who are trying to introduce an "easier" approach to climate control standards in museums do not consider another financial aspect to this problem - final cost of restoration of those artefacts, which will be stored in "less restrictive" environment and damaged a lot more soon. It is a shame to ignore the fact that the present state of climate on planet Earth is more harsh and polluted with agressive chemicals that make distructive impact on works of art even more dramatic. Instead of lessening the reins - it is high time to provide every museum with reliable climate control equipment and substantial conservation/restoration lab, properly staffed. In that way only can we hand over indispensable artistic and cultural treasures to future generations. Otherwise - HD videos and maybe 3-D digital presentations - will be all left.

9 Jun 10
19:33 CET


I'm delighted to see this even as a teaser to the final results. It is impressive the number of dedicated practitioners who have come together to thoroughly examine this question and to thoughtfully, carefully look for a different successful path. Our thanks to them for their care and courage in searching for a better way.

17 Apr 10
1:48 CET


Hi, If we consider that some works are centuries old and these kind of studies, even simulated, only recently have started to be made, I believe that it's still early to achieve a reliable result. We must also consider the supports and mediums to properly set the environmental conditions. Museums are indeed facing some financial issues, even if 2009 and early 2010 were good years in terms of visits. Afterall the mentioned National Gallery of Scotland is quite probably going say goodbye to Turner's "Modern Rome – Campo Vaccino" on July 7th. Nonetheless, taking into consideration the due ethical values, financial issues should not condition the adequate conservation of art. José

12 Apr 10
23:1 CET



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