Paintings and their Environment

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Questions and Answers concluded

12. Is active environmental control in museums responsible use of energy?
This is a matter of definition. It is widely accepted that it is essential to expend energy for environmental control in certain vital contexts: hospital operating theatres for example or institutions such as Kew’s Millennium Seed Bank at Wakehurst Place. For unique and fragile works of art such as Old Master paintings, their future preservation is only guaranteed by providing closely-controlled environmental conditions.

In order to display a collection to best advantage for the greatest benefit to the public, it is necessary to provide Gallery conditions that are safe for the more fragile works in the collection. This enables works of differing sensitivities to be hung together. There are currently no methods of passive environmental control that can meet these requirements fully in a large historic building open to the public for long periods of time. Only ducted air-conditioning systems can provide safe conditions for long-term preservation of paintings collections, and these systems inevitably consume a proportion of the Gallery’s energy budget.

13. What measures does the Gallery take to reduce its energy use?
With the help of the Carbon Trust, the Gallery has recently embarked on a major energy-saving plan designed to reduce energy use by 43% over a four-year period. At the heart of this is the installation of a new, highly efficient combined heat and power plant (CHP) which will bring about total energy saving of 15%.

At the same time, starting in 2011, a programme of installing new light-emitting diode (LED) lamps in the Gallery rooms was begun. LED lights have much lower energy consumption than incandescent lamps and are also more energy efficient than fluorescent lights. They have long operating life-times which lowers maintenance costs. LEDs provide satisfactory colour rendering for paintings and are suitable for the conservation requirements of Old Master pictures. At the completion of this new lighting project, the Gallery will save a further total 5% of its total energy budget. Other energy saving measures will contribute to the overall target figure of 43% reduction.

14. Will future technology solve our problems of effective preventive conservation?
This is hard to predict. For newly-built projects it is possible to improve both the energy performance of buildings and their effectiveness in maintaining relatively stable internal conditions of microclimate naturally. These building characteristics become less attainable in parts of the world where the external climate is extreme. Passive control of conditions is also more difficult to achieve when a building such as the National Gallery receives large numbers of visitors.

For the present, and near future, it is difficult to envisage the provision of stable ‘Class I Museum’ conditions without ducted air-conditioning plant. Many types of collections, however, are less sensitive than Old Master paintings, and less stringent environmental conditions for preservation are possible. For paintings, where active environmental control is not possible, various designs of enclosure can help maintain relatively safe conditions for their protection. However, these inevitably act as a barrier to the best visibility and may require individual monitoring to ensure the safety of the contents.

15. Where can I get more advice on the care of Old Master paintings?
Queries on this subject may be directed to the Scientific and Conservation Departments of the National Gallery via the Gallery’s Information service.

16. Where can I find further published information on this subject?
The standard work on this subject is G. Thomson, 'The Museum Environment', 2nd ed., Butterworths, London, 1986.

For refinements to the Gallery’s specification, see David Saunders, ‘The Environment and Lighting in the Sainsbury Wing of the National Gallery’, ICOM Committee for Conservation, Vol. II, 1993, pp. 630ff.

For advice on the preservation of more generalised categories of cultural material, see David Grattan and Stefan Michalski, ‘Environmental Guidelines for Museums – Temperature and relative Humidity (RH)’ [External link] available from the Canadian Institute for Conservation (CCI). The CCI classification deals with general classes and combinations of materials which results in placing easel paintings in the category defined as ‘very high vulnerability’.

17. Where can I get more advice on other kinds of works of art, cultural objects and collections?
A new document ‘Specification for managing environmental conditions for cultural collections’ (PAS 198:2012) [External link] will be available from the British Standards Institute. This deals in general terms with collections of cultural objects of diverse types, and focuses on reductions in the use of energy in preservation strategies.