The second phase of the Automated Canvas Analysis Project was launched in the summer of 2019. Researchers are reconstructing the rolls of canvas used by Vincent van Gogh. The (provisional) results play a significant role in sequencing and dating Van Gogh’s works.
The Automated Canvas Analysis Project (ACAP) was started in 2007 to develop a computer program together with restorers and art historians, which allows characteristics of the weaving pattern of canvases to be calculated. The calculations are being made using a digitized X-ray of a painting.
The second phase of the project focuses primarily on the reconstruction of the rolls of canvas used by Van Gogh. The aim is to identify each painting from a certain 5 or 10-metre roll of canvas, and to precisely ascertain their position in the roll. This will help us to discover more about how Van Gogh worked. The research will also help to solve issues regarding dating, sequencing and attribution.
For the second phase of the project, Professor William A. Sethares from the Department of Electrical and Computer Engineering at the University of Wisconsin visited the museum for a week early in 2019. The week focused entirely on the start of the second phase of the research, with which Sethares will be closely involved.
Colleagues from inside and outside the museum attended sessions at which the current state of affairs was explained, and the subsequent steps were discussed.
To kick-off the second phase of the project, we reflected on the results from the first phase, in which more than 400 of Van Gogh’s paintings were analysed using X-rays. Sethares also gave an inspirational presentation introducing a related project that has now been completed: Counting Vermeer.
This project analysed nearly all known paintings by Johannes Vermeer. Comprising some 30 paintings, Vermeer’s oeuvre is considerably smaller than Van Gogh’s painted oeuvre, which comprises more than 800 works. The analysis revealed that the dating of various works needed to be adjusted.
What exactly is analysed?
The entire week was focused on ‘counting threads’ of the canvas upon which Van Gogh painted. In the 19th century, canvas was weaved industrially. Weaving is a process in which a horizontal (weft) thread is passed back and forth between fixed vertical (warp) threads.
The pieces of canvas that Van Gogh was sent in the South of France from Paris were cut from large rolls of 2 metres wide and 100 to 150 metres long. These were first cut into 10-metre pieces before being primed on large frames. Art supplies shops sold these rolls in two ways: as canvas per metre, and as ready-to-use canvases in various formats.
Van Gogh ordered his canvas per 5 or 10 metres at Tasset et L’Hôte in Paris, through his brother Theo. Using X-rays of paintings, a specially-developed computer programme can determine the thread density and fairly precisely determine the thread count per cm2. This results in what can be seen as a ‘fingerprint’ of the canvas, which can be used to determine if canvases have been cut from the same roll.
Sunflowers came first
This technique was also used in the research into the various versions of Van Gogh’s Sunflowers. Automated thread counts from X-rays of the Sunflowers from the collections of the Van Gogh Museum and The National Gallery in London were used to determine that the works were made on the same type of ‘standard’ canvas (toile ordinaire), but that the canvases came from different rolls.
The average density of the Amsterdam canvas is 11.4 vertical and 16.9 horizontal threads per cm2, while the London canvas is 11.5 x 17.2 threads per cm2. In the case of Sunflowers in the Van Gogh Museum collection, a direct match was revealed between canvases from a single roll, i.e. canvases that were originally adjacent. The canvas of Sunflowers was revealed to have originally been next to the smaller work Basket of Potatoes (Kröller-Müller Museum, Otterlo).