Achieving painterly effects: the role of the artists’ paint medium
Aviva Burnstock, Head of Conservation, The Courtauld Institute, University of London
Making Art in Tudor Britain
Abstracts from Academic Workshops (2007-8)
Artists’ paint typically consists of coloured material (pigment) bound in a fluid medium. While the present study of Tudor and Jacobean paintings in the National Portrait Gallery includes an investigation of the range of coloured pigments used for each, there has so far been no systematic study of the range of organic materials used to bind the pigments in the works.
The importance of artists’ choice of binding medium to achieve painterly effects is widely acknowledged. Working in different media – oil, tempera, or watercolour, for example - is fundamental to the apprenticeship or training of painters from all periods, either in the context of a workshop or art school education. The use of a range of different media for painting, either closely similar to the materials and methods described in painting treatises or different from them, have been found in a number of technical / analytical studies of paintings. A great number of publications describe the influence of the introduction of oil media for painting in Northern Europe from the twelfth century, and later the impact of its use in Italy. This presentation included images from paintings made using different media, for example the characteristic distinct juxtaposition of parallel strokes of paint for the flesh in a detail from the painting of Saint Lawrence attributed to the Master of the Figline, c.1310-40 (Courtauld Gallery), achieved using egg tempera which is relatively fast drying, with details from a seventeenth-century Dutch still life, where oil bound paint is blended and applied thinly to depict the transparency of fine glass.
Technical studies of a small number of works by Holbein (from the National Gallery) and sixteenth-century German school paintings suggest that the predominant medium used was drying oil. The astonishing range of painterly effects achieved by Holbein might be attributed to his sublime manipulation of the oil medium. The range of painterly effects (evidenced in details from selected paintings from the Holbein group and other sixteenth-century paintings under technical investigation in this project) may also be achieved using oil with additions to change the rheology of the paint. The use of high impasto, for example, for depicting jewellery and costume details; thin translucent coloured glazes and saturated black painted passages (of drapery and background) may have involved the incorporation of oils modified for the purpose, or other organic additives, such as egg, resin, gums or waxes. An artist or workshop might choose to use a particular range of pigments and a similar range of organic binding media might be employed. These materials may be used systematically for achieving different effects in paint by individual painters, in different workshops, or in making copies.
A case is made, therefore, for investigation into the binding medium used for the paint from the National Portrait Gallery works in this study. The methods for organic analysis are reviewed in the context of the options for analysis that are available, and considering the kind of samples that are possible. These include gas chromatography coupled with mass spectrometry (GC-MS), staining tests on paint cross-sections and imaging Fourier transform infrared microscopy (FTIR-ATR).