We present here some further analyses of the paint media of National Gallery paintings. Like our earlier results (note 1–3) they are based on gas-chromatographic examination of the fatty acid content of the samples. In most cases the results are unambiguous and unsurprising and tend to confirm trends noted before, notably the use of walnut oil in the earlier Italian oil painting and its replacement by linseed oil as the sixteenth century progressed.
The samples taken from this extremely thinly painted picture could only be very small. While the first two samples appeared to be essentially egg tempera, possibly contaminated with oil from later additions as with the Bellini, ‘Blood of the Redeemer’ reported before (note 3), the green paint was apparently in oil. The distribution of these media in the layer structure has not, however, been checked by staining.
This picture was considerably overpainted. The original appears to be entirely in walnut oil. Blue repaints in the sky and in the Virgin's dress were found to have been carried out in egg tempera while a sample of brown paint from S. Michael's shield consisting probably of both original and repaint contained both egg and oil. The only other painting by Perugino which has been examined for its medium, the ‘Combat of Love and Chastity’ (Musée du Louvre) painted for the ‘Studiolo’ of Isabella d'Este, is reported to be in egg tempera with any upper layers in oil (note 4).
While the black paint of the man's hat was original and in oil, his black robe was found to be extensively overpainted in a medium which contained egg fats but no oil, and also a considerable proportion of pine resin (strong peak in the position of methyl dehydroabietate on the chromatogram). This corresponds to a repaint medium which has been found in other nineteenth century repaints on some National Gallery pictures notably one by Garofalo (note 1). Blue paint of sky on an added strip along the top of the painting was found to be in egg tempera.
The discoloured blue-green colour of this paint initially suggested the possible presence of smalt. However the pigment was in fact bright blue ultra- marine thinly dispersed in a matrix of yellowed linseed oil which caused the discolouration.
These two paintings are more fully discussed elsewhere in this ‘Bulletin’ (see p.3ff.). Both are in linseed oil in common with other Tintoretto samples analysed (note 1).
Pine resin (methyl dehydroabietate observed on the chromatogram) was found in this sample but its significance is not apparent.
This painting is discussed more fully elsewhere in this ‘Bulletin’ (see p.51ff.). The resin found in Sample 2 probably represents residues of old varnish which often tends to penetrate and discolour azurite-containing paint layers, especially the dark blues of the Virgin's robe.
The samples examined were paint fragments collected from the floor after this painting had been attacked and damaged by a visitor. Consequently they cannot be located precisely on the painting.
These ratios seem sufficiently different for one to believe that two different oils were used in the painting. We had hoped to encounter poppy oil once again in the whites as with the painting by Drouais reported before (note 3). Too few samples were examined for general conclusions to be drawn regarding the use of the two oils.
The medium here could be either walnut oil or a mixture of linseed and poppy oils. Similar P/S ratios (3.0, 3.9, 3.4) were reported with samples from two other paintings by Manet, the ‘Déjeuner sur l'herbe’ and ‘Le Balcon’ (Musée du Louvre) (note 5).
Mills, J.S. and White, R., 'The Gas-Chromatographic Examination of Paint Media. Some Examples of Medium Identification in Painting by Fatty Acid Analysis', in N. Brommelle and P. Smith (eds.), ‘Conservation and Restoration of Pictorial Art’ (London 1976) pp.72–7.
Mills, J. and White, R., 'Analyses of Paint Media', ‘National Gallery Technical Bulletin’, 1 (1977), pp.57–9.
Mills, J. and White, R., 'Organic Analysis in the Arts: Some Further Paint Medium Analyses', ‘National Gallery Technical Bulletin’, 2 (1978), pp.71–6.
Delbourgo, S., Rioux, J-P. and Martin, E., 'L'Analyse des Peintures du Studiolo d'Isabelle d'Este au Laboratoire de Recherche des Musées de France. II: Étude analytique de la matière picturale', ‘Annales du Laboratoire de Recherche des Musées de France’ (1975), pp.21–8.
Delbourgo, S. and Rioux, J-P., 'Manière et Matière des impressionnistes. Contribution à l'étude de la matière picturale', ‘Annales du Laboratoire de Recherche des Musées de France’ (1974), pp.34–42.