2.6 Condition, past conservation treatments, interventions and ageing
X-radiography is an important method for revealing the state of preservation of a painting, especially for making damages and losses in a painting visible that may be less noticeable on the surface when covered with retouching. The technique can also provide information on past interventions and treatments. The scanning of X-radiographic films at high resolution also allows for the identification of micro-features in the paint associated with ageing of the paint layers. The following examples illustrate these aspects in more detail.
2.6.1 Evidence of excellent condition
Vermeer’s The Guitar Player (L35) is in an exceptionally good state of preservation. The canvas has never been lined, and is still mounted on its original strainer with small wooden pegs. In contrast with the metal tacks that were added later to help tension the canvas, the wooden pegs do not register in the X-radiograph. Apart from small losses along the edges of the canvas, no paint loss or damages can be discerned in the X-radiograph .
2.6.2 Evidence of poor storage
The X-radiograph of Diana and Her Nymphs (L01) shows the painting is in fair condition. Several vertical black lines, running through the figure of Diana, left of center  correspond to areas where paint and ground are missing. Since X-rays are not absorbed in these areas the damages show up black in the X-ray image. Together with the large losses around the perimeter of the painting, this suggests the canvas was rolled up and poorly stored in the past.
2.6.3 Evidence of exposure to poor climate conditions
When Girl with a Pearl Earring (L22) was bequeathed to the Mauritshuis in 1903, the painting was reported as being in a ‘deplorable state of neglect’. Photographs taken at the time, as well as written documents showed the painting suffered from extensive paint loss. The painting has since been restored several times, and although the paint losses are no longer visible they can still be seen in the X-radiograph . When the painting was investigated prior to its treatment in 1994-1995 inexplicable white dots were observed in the X-ray in areas that did not contain lead white. During the subsequent cleaning of the painting it was discovered that the white dots in the X-ray were small upturned flakes of original paint. It would seem that when the painting was lined in 1882, the adhesion of the paint was very poor and many loose paint fragments were displaced and pressed into the paint surface. During the 1994-1995 treatment a total of 38 paint fragments were removed.1
The X-radiograph of The Guitar Player demonstrates the excellent state of preservation of the painting. Except for a few tiny losses along the edges of the canvas, no paint loss or damages can be discerned in the X-radiograph.
X-ray of Diana and Her Nymphs. The numerous areas of paint loss around the edges and along the vertical cracks left of center suggest the painting was rolled up in the past.
X-ray of Girl with a Pearl Earring. Although the numerous paint losses have been retouched and are no longer visible to the naked eye, they can still be seen in the X-radiograph. Where the paint and ground are missing, X-rays are not absorbed and these areas appear black.
2.6.4 Evidence of an accident
Although otherwise in good condition, View of Delft (L12) was damaged in 1876 when a curtain rod fell in the galleries, making a hole in the center of the sky. The damage was restored in the same year by W.A. Hopman (1828-1910). Although after restoration the damage is no longer visible, it is still clearly visible in the X-ray as a black area in the sky [4a, 4b].2
Detail of the sky after restoration of the damage in Vermeer’s View of Delft.
Detail of the X-radiograph of View of Delft, showing the damage in the sky.
2.6.5 Evidence of vandalism
In 1971 Vermeer’s The Love Letter (L30) was stolen from an exhibition in Brussels where it was on loan from the Rijksmuseum. Brutally cut out of its frame, the painting incurred severe paint losses along all edges. After its return to the Rijksmuseum, an international committee decided The Love Letter (L30) should be restored as invisibly as possible, and that all areas of loss and damage should be carefully retouched to maintain the painting’s illusionistic quality.3 The extent of the damages can still be seen in the X-radiograph, where original paint is missing [5a, 5b].
Luitsen Kuiper filling losses in The Love Letter during the 1972-1973 restoration (Photo: Rijksmuseum Amsterdam).
X-ray of The Love Letter after the 1972-1973 restoration. The damages in the canvas show up black in the X-radiograph.
2.6.6 Evidence of heat damage
The X-radiograph of Woman Reading a Letter (L17) shows the painting has suffered extensive damage along the bottom edge and is in only fair condition. During the 2010-2011 treatment of Woman Reading a Letter (L17), X-radiographs proved very useful in mapping a distinctive damage pattern consisting of tiny holes and blisters in the paint surface. The small circular losses in the paint layer filled with dirt and residues of discolored varnish, together with the raised tiny blisters, interfered with the overall legibility of the painting. Apart from a severely discolored varnish and a large, old repair at the bottom edge, this damage pattern was one of the main reasons the museum wished to treat the painting. A first step in establishing the probable cause of the degradation was to plot the distribution of the damages over the paint surface. By zooming in on the high resolution scans of the X-radiograph of Woman Reading a Letter (L17) it was possible to distinguish the micro features as dark grey or black spots, including those that were not readily visible on the paint surface [6a, 6b]. Analysis of paint cross sections showed the paint layers were extensively deformed in the damaged areas, indicating exposure to raised temperatures. It also became obvious that the damage to the paint was not confined to the blisters and holes on the surface, but that the paint has an extremely porous structure (bubbles) throughout the paint layers, from the ground up through to the paint surface. It appeared that Vermeer’s Woman in Blue Reading a Letter (L17) had been overheated, most likely during a past lining procedure, causing the paint to blister. Some of these small blisters erupted at the surface, leaving small circular losses in the paint surface.4
Detail of the upper left wall in Woman Reading a Letter before the 2010-2011 treatment, showing small clustered damages related to heat damage.
Detail of the X-radiograph of Woman Reading a Letter, showing damage in the upper left wall. Even though these areas are obscured by dirt or retouching, the damages are visible as small dark grey or black spots in the X-ray.
2.6.7 Evidence of lead-soap aggregate formation
The red rooftops at the left edge in View of Delft (L12) [7a, 7b] now appear pinker in tone and show a remarkable grainy texture with masses of protruding white lumps.5 Visual inspection of these white lumps in the past suggested Vermeer added sand or large lumps of lead white pigment to his paint in order to create pronounced textural effects. Through analysis we now know that the lumps were not added deliberately, but are a frequently occurring type of chemical degradation caused by interactions between metal (ions) and fatty acids in the paint, which can take on various manifestations, including aggregates that break through the paint surface. The whitish lumps are also visible in the X-radiograph of the painting, where they show up as tiny light spots in the dark paint of the roof tops [7c].
Microscope detail of the red rooftops in View of Delft (L12) showing masses of protruding lead soap aggregates in the red paint of the rooftops (Image: A. van Loon).
Detail of the red rooftops in View of Delft. The paint appears pinker where the lead soap aggregates have broken through the paint.
Same detail of the red rooftops in the X-radiograph of View of Delft. The lead soap aggregates are visible as tiny white spots. The light part of the X-ray is due to the stretcher bar.
1 K.M. Groen et al., ‘Scientific Examination of Vermeer’s Girl with a Pearl Earring’, Vermeer Studies. Studies in the History of Art 55 (1998), pp. 169-183, esp. pp. 169-170; J. Wadum, R. Hoppenbrouwers, and L. Struick van der Loeff, Vermeer in het licht: Conservering, Restauratie en Onderzoek: Verslag van de Restauratie van het Gezicht op Delft en het Meisje met de Parel van Johannes Vermeer, The Hague/Naarden/Wormer 1994, p. 24.
2 L. Struick van der Loeff, Vermeer in het licht: Conservering, Restauratie en Onderzoek: Verslag van de Restauratie van het Gezicht op Delft en het Meisje met de Parel van Johannes Vermeer, The Hague/Naarden/Wormer 1994, p. 31.
3 N. Ex, Zo goed als oud. De achterkant van het restaureren, Amsterdam 1993, pp. 116-119.
4 I. Verslype, ‘The restoration of “Woman in Blue Reading a Letter” by Johannes Vermeer’, The Rijksmuseum Bulletin 60 (2012), pp. 2-19, esp. pp. 5-7.
5 P. Noble et al., Preserving our Heritage: Conservation, Restoration and Technical Research in the Mauritshuis, Zwolle 2009, pp. 176-177 and A. van Loon, 'De korrelige verf in Vermeers Gezicht op Delft: Nieuwe onderzoeksgegevens', kM 2009, pp. 10-13.