Picture Meeting 15 april 2010

Picture Meeting Report, April 15th 2010

This time the Picture Meeting, which took place on April 15th, had no binding theme; the various lectures presented some of the current research projects in the Netherlands and the United Kingdom. Although the meeting was somewhat shorter than anticipated, because of the farewell lecture by Ernst van de Wetering, it was a lively and divers day, with lots of discussions.

The first lecturer, Sophie de Behault (UvA/ SRAL), gave her presentation about Blue-hued scattering in the Dutch Golden Age paintings. Blue-hued scattering – the subject of her master thesis at the UvA – is the phenomenon that a paint layer consisting of black and white pigments can be blue in appearance. Blue hued scattering can be observed in everyday life: both a clear blue sky and veins under the skin are not – in fact – blue, but appear so to the eye. This effect is closely linked to the so-called ‘turbid medium effect’: a semi-transparent light layer over a warm and dark underlayer appears cooler. Many artists made use of this effect; a good example is Rubens who used it in the flesh of his figures. The results of Sophie de Behault’s research so far have wielded the hypothesis that blue hued scattering in paint layers is caused by unusually small particle size of the lead white that was used in the top layers.

The second lecture was an open question to the audience, exactly the type of presentation that the Picture Meeting is meant up for. Aviva Burnstock (Courtauld Institute of Art) presented An intriguing underdrawing in a Tudor painting. The painting in question is an anonymous portrait dated 1550, but otherwise unsigned. Infrared reflectography has yielded an unexpected and very interesting underdrawing of an architectural landscape that is totally unrelated to the painted portrait. It has been drawn with a fluid medium in very characteristic, almost whimsical, wavy lines. Clearly the panel was underdrawn for a different subject, possibly for a different patron, but in the end it was re-used for the portrait instead. The architecture in the drawing shows a clear Antwerp Mannerist style, but so far an artist’s name has not yet been attached to it. Dirk Vellert (c.1480-1547) and Lucas de Heere (1534 – 1584) are now being researched as possible candidates. Needless to say that the speaker would highly appreciate any additional suggestions.

Next, Laura Hind (student easel paintings conservation, Courtauld Institute of Art) presented her research about Surface whitening in 20thC Spanish paintings at Dudmaston Hall, UK, which was the subject of her final thesis. The research was done in collaboration with ICN.

Three Spanish paintings from the fifties and sixties of the twentieth century, in a  British collection of modern art, and all suffered similar looking paint defects.  Since they all had the same exhibition history, the defects – a whitish material on the paint surface – were thought to be the same phenomenon. Analyses however showed that the white material was different in all three cases. In one case it was free fatty acids and in two cases it was – different – salts dissolved from the paints layers in water and migrated to the surface.

The next presentation – in Dutch as an exception – was called Sturgeon lining Russian School. It was given by Wassily Khudiakov, a private conservator trained in Russia, but with an internship and working experience in the Netherlands. He gave an interesting and very practical lecture on how to perform a sturgeon lining. This type of lining he was taught at Russia; it has a long tradition there and is still frequently carried out. Wassily presented the lining step by step, using the photo’s he took of a sturgeon lining he himself carried out on a 19th C painting. This type of lining is virtually unknown in the Netherlands, which of course has quite a different lining history, namely that of the wax-resin lining. Paste or animal glue linings that were carried out in the past are still frequently encountered however.

Joris Dik (Technical University Delft) gave a lecture on the Deterioration of cadmium yellows in Ensor and Van Gogh. This research project is a collaboration of the TU, the University of Antwerp and the Kröller-Müller Museum. The finding – by Luuk van der Loeff – of discoloured yellow paint with white crystals on the surface on a painting by James Ensor, was the start of this project. A sample of this paint area was analysed using different methods, including µXRD at the European Synchrotron Radiation Facility in Grenoble. Analytical results showed that cadmium yellow paint (cadmium sulphide) was used by the painter, but it had been oxidized into cadmium sulphate. This explained the white crystals on the surface, but unfortunately not (yet) the uniform darkening of the paint layer. A similar case was found on the painting Flowers in a blue vase by Vincent van Gogh, although, due to its conservation history, this was now in a much more dramatic state, where the paint had not only discoloured, but almost crumbled away under the varnish.

The subject of the next lecture was Whitish deposits on the inside of the glass in microclimate frames. This project – presented by Petria Noble – is a collaboration between the lecturer and Annelies van Loon (both Mauritshuis). It has been found in many instances, in many museums in the past that on the protective Mirogard glass – when used in so-called microclimate boxes – a whitish haze would form over time. At the Mauritshuis this whitish haze has been systematically recorded when found over the past decades. This has yielded interesting results. As was the case in similar examples in other museums, the haze consisted of free fatty acids. But because of the overview at the Museum, it was found that the paintings that had produced a haze, had hung against the outer walls in the museum. On these walls it has always been more difficult to maintain a constant climate. It was discovered that the free fatty acids mostly came from medium rich paint areas, often the darker layers in a painting; this made the deposits of the whitish haze on the glass into a negative form of the actual painting. Some of the results seem to suggest that the type of glass – Mirogard – plays a role in this phenomenon, but this needs further study.

The last lecture of the day was given by Jaap Boon (JAAP enterprises) and dealt with Mechanical weakness of Vermeer’s paints in The Art of Painting. This famous painting by Vermeer was the subject of the exhibition Vermeer, the Art of Painting – Analysis of a Masterpiece in Vienna. For conservation treatment, the exhibition and the catalogue, the painting was extensively researched in all fields. From a conservation point of view, the painting is a problematic one, with a long history of micro-flaking of the upper paint layers. Researching both the painting technique used by Vermeer and the conservation history, an attempt was made to answer the question why the micro-flaking was occurring. Jaap Boon found that in the top layer – the layer that was actually flaking off – unusually fine particles of lead white (50-100 µm) were used. This fine particles caused so-called rift cracking, which results in delamination between the top layer and the layers underneath. The form of this type of rift crack is called ‘Warner line’ and it is usually found in glass. Interestingly the choice for the fine lead white particles may have been to create a thin semi-transparent layer over the darker underlayer, making use of the turbid medium effect that was also presented by Sophie de Behault.

Verslag: Esther van Duijn

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