The Making of Colour | Pigments in Focus

November 2023

Pigment analysis, as with any other scientific test, cannot constitute the meaningful authentication of an artwork standalone. Forgers have, historically, been able to reverse engineer pigment analysis tests.

Peter Paul Rubens, The Judgement of Paris, c.1636, oil on oak, National Gallery, London.

Key Takeaways:

  • Pigments are hardly ever used by themselves. Binders must be used to ‘fix’ the pigments.
  • Pigment analysis, as with any other  scientific test, cannot constitute the meaningful authentication of an artwork standalone.
  • Forgers have, historically, been able to reverse engineer pigment analysis tests.

Colour has formed the basis of human creative production, but what exactly is colour and how have artists created and used it differently across an endless array of eras, geographies and traditions? Paint, fundamentally, consists of billions of individuals grains of pigment, glued together using a binder. Pigments are hardly ever used in their raw form and the techniques of ‘fixing’ paint with a binder are endless.

Neolithic cave paintings, for example, had colour fixed in what is thought to be an entirely serendipitous process of limestone cave walls containing silica which fixed the pigment and incidentally enabled the preservation of works like that of the Maltravieso cave in Cáceres, Spain.

One of the earliest man made binders used in painting, however, is gum arabic which originally consisted of the hardened sap from the North African acacia tree. Gum arabic was used, and continues to be used, especially in the context of watercolour painting because it is an easily dissolvable binder. Beeswax, also, has, and continues to be used as a binder to produce encaustic paint (made of molten wax) while egg yolk and milk (in the form of casein) have been historically used as the binding agent for tempera.

The most widely discussed technique in art history, however, is the production of oil paint and the integration of pigments with drying oils including linseed, walnut, poppy or safflower oils. When these drying oils react with oxygen they are transformed from a liquid to a solid state. From Rubens to Lucien Freud to Jenny Saville, the liquid, slow-drying qualities of oil paint have enabled artists to explore new possibilities of painting and, in particular, figuration because of the medium’s textural qualities.

Perhaps most significant is the fact that oil paints require far less oil than, for example, watercolours require gum arabic, in order for the colour to be ‘fixed’. This enables a density of colour that has meant that, for artists, colouration has been able to take precedence over the drawn line. The binder, in this way, played a crucial role in arguably the most significant art historical discourse in the western tradition – disegno versus colore – colour versus line. This Renaissance paragone also became known as the debate between Rubenists and Poussinists in the French Royal Academy of Painting and Sculpture in the late seventeenth century.

It is through mixing pigments with specific binders that enables pigments to be transferred across a variety of uses, not only in the context of the production of painting but also for the production of inks, household paint, plastics and paper to name a few.

In the context of forgery, however, the production of paint serves a specific role – particularly in the reverse engineering of pigment analyses. At Hephaestus, we have seen a number of forgeries pass rudimentary pigment analyses which is precisely why we have developed a sequential protocol of scientific tests. In this way, if pigment analysis is the extent of scientific testing on an artwork, only what might be termed ‘garden variety’ forgeries might be found. Hephaestus has long referred to an ‘arms race’ between forgers and art market participants, a race that the art market has failed to win countless times because of a lack of sequenced testing and, of course, junk science. Understanding the chemical compositions, techniques and applications of various painting practices and media is vital not only in understanding art history and its academic discourses but, significantly, forgers’ intervening techniques.

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