Oscar F. van den Brink, Gert B. Eijkel, and Jaap J. Boon

FOM Institute for Atomic and Molecular Physics

PAINT BASED DOSIMETRY OF THE MUSEUM ENVIRONMENT

ABSTRACT

Painted works of art on display in museums are subject to many environmental factors. Air pollutants that diffuse into the museum from the outside, and gases emitted from building materials and equipment inside the museum react with the works of art. Visitors of the museum are another source of air pollution. Other factors such as light intensity, temperature, and relative humidity determine the rate at which these reactions occur. As these factors can have both synergistic and inhibitory effects, the overall effect of the environment is a non-linear function of these factors. Hence, unless the nature and extent of interaction of the factors are known in detail, separate measurement of each of these individual factors does not result in an accurate assessment of the effect of the environment on the works of art.

Together with our European project partners at Birkbeck College, London and IROE-CNR, Florence, we have developed a test system based on traditional artists' materials to measure the overall effect of the museum environment on paintings. Changes in the chemical composition of these test systems are used as indicators of the environmental impact. Mock paintings were prepared using a mixture of whole egg and mastic as the binding medium. Non-pigmented test systems as well as systems pigmented with lead white, azurite, sienna, smalt and curcumin were used. A calibration set obtained by controlled exposure of the test systems to light, elevated temperature and to air pollutants (NO_x, SO₂). The chemical composition of the calibration set was analysed by mass spectrometric techniques. Changes in cholesterol, glycerolipids and triterpenoids, which point at processes such as hydrolysis, oxidation and polymerisation were identified. The mass spectrometric results were used to derive the degree of chemical change in the test systems. In the paper we present the methodology used to derive the degree of chemical change. Moreover, we present the comparative results of a 9 months' exposure of our test systems to the selected museum environments in the Rijksmuseum (NL), the Tate Gallery (UK), the Uffizi (It), the Alcazar (Sp), and Sandham chapel (UK).

A paper in press for Thermochimica Acta describes the work in more detail.

Oscar F. van den Brink, Gert B. Eijkel, and Jaap J. Boon
Unit for Mass Spectrometry of Macromolecular Systems
FOM Institute for Atomic and Molecular Physics
Kruislaan 407, 1098 SJ Amsterdam
The Netherlands
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