By Francesco Caruso, Sara Mantellato, Noëlle L.W. Streeton, and Tine Frøysaker
The study of original artists’ materials is an invaluable opportunity for conservators, conservation scientists and art historians to uncover information about painting techniques, degradation phenomena, production issues, style preferences and so on. When Fortidsminneforeningen (the National Trust of Norway) gave us the chance to examine the original paint tubes from the Norwegian artist Harriet Backer (* 21 January 1845, Holmenstrand – † 25 March 1932, Oslo) it was clear that this could be the first step in a larger project on Modern female painters.
Harriet Backer, a contemporary of Edvard Munch, was one of the most important painters of her generation. Literature has previously summarized her artistic programme as follows: “A classical, perspective composition combined with a modern apprehension of motif and colouring”. It is the latter “modern apprehension of […] colouring” that also stimulated this study.
We retrieved 259 paint tubes, used by the artist between 1904 and 1909, from a wooden box (also containing Lefranc’s varnish bottles and some paint rags) at the medieval stave church at Uvdal in Eastern Norway.
A massive campaign of documentation was initiated by cataloguing the 259 paint tubes, transcribing their labels (or their remains) and shooting HD pictures in recto and verso. At this stage, some of the outcomes had already emerged.
Backer did not have any blacks and gave a strong preference to blues, yellows and reds. She favoured the colours by the German manufacturer Dr. Schoenfeld & Co. (today, Lukas-Nerchau) whose archives in Düsseldorf were completely destroyed during the Second World War. In fact, Dr. Schoenfeld & Co.’s colours represent 83% of the grand total of the paint tubes found in Backer’s paint box.
During this first phase of the project, we realized that the previously published scientific articles and monographs on historical paint tubes mainly focused on the characterisation of the organic part. So far no technique or study had ever obtained accurate quantitative information of the inorganic fraction (i.e., pigments, siccatives, additives). In view of this gap in knowledge and by taking inspiration from a work on cementitious materials, we developed and validated a new and robust method by using an advanced micro-destructive technique, Inductively Coupled Plasma-Optical Emission Spectroscopy. Out of the 259 historical paint tubes, we took samples (in the order of a couple of milligrams) from 57. These samples were taken from the tubes where the cap could be easily unscrewed or those without a cap. The samples were then incinerated, treated with powerful acids, filtered, diluted and analysed. From these, 17 elements (aluminium, barium, cadmium, cobalt, chromium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, lead, sulfur, silicon, strontium, zinc) were accurately quantified to obtain a sort of chemical fingerprint for each analysed colour.
Several interesting aspects related to the production of these paint tubes between the end of the 19th century and the beginning of the 20th century were brought to light. For example, the compositions of the brilliant yellows and the finest crimson lakes were clarified, and the many impurities/additions present in the viridian tubes were identified and quantified. The outcomes of this work will be useful i) to give complementary insight into the results from non-destructive techniques to study Backer’s paintings; and ii) to provide information about the production of late 19th- to early 20th-century (especially German) paint materials.
It is our hope that, in the future, other colleagues will adopt this technique so that these results will be comparable. The project on Harriet Backer’s paint tubes will continue with the study of their organic fraction in collaboration with the Academic Materials Research Laboratory of Painted Artworks (ALMA) at the Institute of Inorganic Chemistry of the Czech Academy of Sciences, Prague.
More comprehensive and detailed information can be found in our open-access paper in Heritage Science: https://doi.org/10.1186/s40494-018-0244-8
The full article can be found in "News in Conservation" Issue 74, October 2019 here: https://issuu.com/nic_iiconservation/docs/nic-magazine-october-2019-issuu
Francesco Caruso, Ph.D., was Associate Professor of Conservation and Conservation Science at the University of Oslo from 2016 to 2019. In August 2019, he became head of the analytical laboratory at the Swiss Institute for Art Research (SIK-ISEA) in Zurich. His main research interests lie in the development and application of analytical methods for the conservation of cultural heritage and the materials science aspects related to it.
Sara Mantellato, Ph.D., has been a postdoctoral researcher at ETH Zurich since 2018 (and Ph.D. student from 2012 to 2018). She is mainly interested in the rheological properties of admixed cementitious systems and analytical methods for their characterisation.
Noëlle L.W. Streeton, Ph.D., has been an associate professor of conservation at the University of Oslo since 2010. Her main research interests concern historical painting practices, late-medieval painting and polychrome sculpture, chemistry of artists’ materials and the politics of cultural heritage.
Tine Frøysaker, Ph.D., has been a professor of paintings conservation at the University of Oslo since 2011 (and associate professor from 2005 to 2011). She is, at present, interested in the conservation and materials of Edvard Munch and Harriet Backer and of medieval painting and polychrome sculpture.