The Provenance of Artists' Materials

Image courtesy: Hephaestus Analytical

Provenance research focuses on an artwork’s history from the moment it leaves the artist’s studio through to the present day. Scientific analysis extends this timeline further. By allowing us to peer beneath the surface of a work we can view it as a product of its constituent material parts: the support, pigments and binder. Each component has its own provenance, which offers intriguing insight into the artist’s practice and the painting’s geographic origin. The documented history of a painting’s successive ownership after it leaves the artist’s studio is vital in ensuring its legitimacy; in much the same way, the undocumented history of the materials from which a painting is made is important and compelling in revealing its integrity.

Dendrochronology 

Although dendrochronology is often associated with the absolute dating of panel paintings, it can in many instances establish the geographical origin of a panel. Simply put, the width between each concentric tree ring corresponds to a year’s growth. Adverse growing conditions result in stunted growth producing narrower rings, while favorable conditions produce wider rings. When the number of rings and their widths are plotted on a graph, the age and origin of a panel can be calculated. Since trees growing in the same climatic region generally share the same growth stimuli such as temperature and rainfall, their ring patterns are similar, allowing us to establish geographic signatures and identify their presence in panels. 

A large number of panel paintings have been analyzed using dendrochronology, yielding a sizable database where correlations and patterns become apparent. For example, As noted in the article “New evidence for dendrochronological dating of Netherlandish paintings“ many western and northern European artists did not use panels produced from trees indigenous to the area in which they lived, rather they purchased imported panels from the Baltics. There are instances where multiple panel paintings produced in the same workshop originated from the same tree. 

Dendrochronology is primarily used in authentication as it provides a precise and absolute dating technique, yet it also shines a light on artistic practice: if an artist’s workshop only used panels imported from Poland, there may be grounds for suspicion if an unknown painting alleged to be by the same studio was painted on a panel from a completely different region, such as Italy, regardless of whether it dated from the correct period.

Lead isotope analysis

Lead white, the ubiquitous pigment found in almost all Western art can also be traced to its geographical origins. Lead has four naturally occurring isotopes, 204Pb, 206Pb, 207Pb and 208Pb, found in different concentrations in rocks around the world. Accurate tracing is possible because different regions have different “signature” geochemical conditions, which result in characteristic abundance ratios among the four isotopes in lead ore. Thus, we can trace the lead present in pigments back to the mine where the ore was extracted.  

Although some mines have overlapping isotopic compositions, the variance between some regions is statistically significant. For example, it is possible to differentiate between lead white from transalpine and cisalpine sources. In the case of Van Dyck, an artist who painted on both sides of the Alps, we are able to discern whether the picture was completed using pigment purchased from a Flemish or Italian source by looking at the isotope abundance ratios alone, which could be utilised to contextually date or authenticate a work.  

As is the case with analysing wooden panels, a complicating factor in lead isotope analysis is the international trade of goods and artist’s materials. For instance, despite never visiting the UK, the likely source of the lead used in Vermeer’s Girl with a Pearl Earring is a mine in the Peak District. Given artists’ predilection to use the same colourman however, narrow clusters for the lead white used by individual artists and studios can be identified.

Craquelure

As a painting ages, a fine network of cracks appears on its surface. The artist’s technique and materials, as well as the painting’s environmental history develop its craquelure patterns. These patterns can be analysed mathematically so that correlations within an artist’s body of work are identifiable, or, more broadly, to identify art from a particular region or date. A basic example is to compare the difference between the characteristic craquelure patterns of Italian, Flemish, Dutch and French artists: 

The pioneers of this research described craquelure as an 'unintentional signature’ that develops as a painting responds to its environment. Aside from its use in identification techniques, reproducing the precise craquelure patterns produced by the environment since the work’s production date is significantly challenging. At Hephaestus Analytical we are taking things a step further and are using machine learning to reveal deeper craquelure signatures so as to identify those characteristic patterns belonging to clusters of artists. Craquelure is one part of a suite of tests that we are building to eliminate forgery from the art markets, and create the highest evidentiary standards in the authentication of art.

So, tell us, what’s the craquelure like on your painting?