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My first task of the day is to take some samples from a painting that is undergoing restoration, so I head off to the conservation department, down the corridor from our laboratory. The conservator is removing the darkened varnish and old discoloured retouchings from the painting. We discuss the questions that have arisen, which I should be able to answer by analysing samples. We need concrete evidence that the retouchings are later paint, not applied by the artist, and I can provide this by identifying the pigments in the retouchings, because the pigments available to artists have changed with time. To get some information about what the colour originally was, I also take a few samples from other areas of the painting to study the technique and materials and to look at colours that may have deteriorated. The conservator will not restore the paint to the original colour--this would involve repainting the area, which is regarded as unethical--but my technical study will aid the restoration and help us understand how time has changed the appearance of the painting.

The ongoing research into the history of painting technique and into how artists' materials degrade is a central part of our department's work. It provides a basis for interpreting the results of pigment analysis on overpaint and restorations and for choosing humidity conditions and light levels in the galleries. We also work closely with the art historians in the gallery, because our work can be useful to art historical studies. There is still much to discover, which is one of the motivating aspects of my job. The work is quite varied, because interpretation of the analytical results requires a multidisciplinary approach covering branches of both art and science. I need to know about the art history of the paintings I am studying and to read historical literature such as treatises on painting techniques and artists' handbooks. We look not only at samples from the painting, but also at x-ray photographs, infrared photographs, and of course, the painting itself. This fundamental academic research is perhaps quite similar to that in a university, but we use the results of it on several different levels. We publish it in specialist journals, including our own annual National Gallery Technical Bulletin, and also write about our work in exhibition catalogues for a much broader audience.

A Conservationist's Career Path

My first degree was in natural sciences, specialising in chemistry, followed by a 3-year postgraduate diploma in the conservation of easel paintings. I started work at the National Gallery in 1992, after a 6-month studentship in the scientific department. The broad nature of my first degree, which included materials science and crystallography as well as straight chemistry, has proved very useful. The analysis of the materials in paintings involves all these to some extent. The postgraduate diploma course is designed for students who intend to become painting conservators. (A portfolio of artwork is required for an application.) Increasingly, people entering the field of conservation science, specialising in paintings, have training in conservation; it provides a good grounding and understanding of the field. It is a rather indirect route into the field, but there are few other opportunities for formal training in conservation science. The Royal College of Art runs an M.A. course in conservation, in conjunction with the Victoria and Albert Museum, and occasionally accepts students who wish to specialise in conservation science. My colleagues in the scientific department have different, and rather diverse, backgrounds. Several of them have Ph.D.s in chemistry, but all have had a long-standing interest in paintings: They attended university art history courses, for example, or became involved in conservation-related research projects while studying chemistry.

Back in the scientific department, I examine the samples to make some initial decisions about what type of analysis to carry out. The samples that we take are very tiny, less than a pinhead in size, so they have to be manipulated under the microscope. I place the samples in moulds and embed them in polyester resin so that I can prepare cross sections of the paint layers. In the cross sections I am able to see the layers beneath the surface of the paint, including the preparation on the support, which can be characteristic of the time and place a picture was painted.

I put these samples aside to let the resin set and join the other staff members in my department for coffee. This is a chance for us to meet to discuss and combine our work on the paintings in the National Gallery collection. We work closely together but study different aspects of the physical constitution of the paintings and their conservation. My speciality is pigment analysis. We have two organic chemists who use gas chromatography-mass spectrometry and Fourier transform infrared microscopy to analyse the binding medium (such as linseed oil or egg yolk) that holds the pigment particles together to make a paint. A colleague carries out high-performance liquid chromatography on the organic dyestuffs that are found in some pigments; this colleague is also a specialist in the historical literature on painting technique. Other colleagues are involved in high-resolution accurate colour digital imaging of paintings and accelerated ageing experiments on test samples of unstable pigments to monitor the effects of humidity and light.

I spend an hour or so at my computer continuing work on a paper that I am writing about the blackening of the red pigment vermilion (mercury sulphide) for a conference on the deterioration of pigments. This paper combines the accelerated ageing tests carried out by my colleague with observations and analyses I have made on the paintings themselves. We need to know about the historical methods of manufacture of vermilion to ensure that the test samples accurately mimic the behaviour of the pigment in the paintings, some of which date from as early as the 14th century. I have also drawn on studies by mineralogists about the photosensitivity of cinnabar, a mercury sulphide mineral with the same composition as vermilion. Writing about my research is important, because it makes the results available to others in the conservation field. Most museums do not have a scientific department, so very few people are carrying out this type of research.

Postgraduate Courses in Painting Restoration (Specialising in Easel Paintings)

Our starting point in the analysis of samples is examination under the optical microscope. Many pigments can be identified simply by their appearance at high magnification, particularly the coarsely ground mineral pigments in pictures painted before the 19th century. Other techniques that we use when we want to examine a sample in more depth are energy dispersive x-ray (EDX) analysis in the scanning electron microscope (SEM) and x-ray diffraction. I spend the afternoon analysing samples in the SEM. We can find out which elements individual pigment particles contain and look at particle shapes. EDX analysis in the SEM has transformed microanalysis: 20 years ago most pigment analysis was done with laborious microchemical tests.

I also use the afternoon's work as a teaching opportunity for the student who is working with us for a year. She already has a diploma in the conservation of easel paintings and some previous experience in the analysis of pigments, which gives an indication of the kind of qualifications needed to become a conservation scientist. Even so, there are few jobs available. A dedicated interest in paintings, a versatile approach, and an ability to do historical as well as scientific research are needed. But the job is enjoyable and rewarding, studying beautiful paintings and contributing toward the preservation of our cultural heritage for future generations.