By the early fifteenth century, painting in oils was already technically mature in the northern Renaissance. The first truly great masterpiece to use pure oil technique, and still one of the most important European works of art, is the huge altarpiece in Saint Bavo’s Cathedral in the Belgian city of Ghent, which was dedicated there on 6 May 1432.
The Ghent Altarpiece, as it’s now known, is also one of the most studied paintings, with many thousands of pages devoted to theories as to how it was made. With the benefit of more modern methods of analysis and investigation, some of the earlier accounts have been shown to be wrong. For instance, the proposal by Max Doerner that egg tempera was used in its painting has now been rejected.
The panels which make up the altarpiece are generally accepted as being painted by the van Eyck brothers in their workshop in the city of Bruges, to the north-west. Hubert, the older and more experienced, may have obtained the original commission, thought to be from Jodocus Vijd, who died in 1439, and his wife Isabella (or Lysbette) Borluut, who died in 1443. Vijd was a senior councillor of the city, an affluent merchant, and originally intended the altarpiece for the family chapel in the church of Saint John the Baptist, which was reconstructed as Saint Bavo Cathedral in 1559-69.
Work seems to have started, probably under the direction of Hubert van Eyck, in about 1424. As the staff of the workshop worked on preliminary designs and studies, Hubert was working out its dimensions, thus ordering the supports and frames from a specialist joiner. In turn, they sourced suitable Baltic oak which had been imported directly into Bruges, now recognised as a major centre for trade at the time.
The oak panels were cut to size, sized with glue derived from animals, and prepared with traditional chalk grounds, and were probably supplied ready for Hubert to design the principal scenes on them. This he did using either charcoal or graphite and an organic black ink. Unfortunately Hubert then died on 18 September 1426, when work on the altarpiece was in full swing, but far from complete.
By this time, the younger brother Jan had established himself as a master painter too. Paintings such as his Diptych of The Crucifixion and The Last Judgment (c 1420-25), of which this is the left panel, demonstrated that he too was capable of taking on a complex oil painting.
There seems to have been a short hiatus before Jan took over the Ghent Altarpiece project, perhaps for contractual adjustments, and it probably wasn’t until January 1430 that work on it resumed. By its dedication on 6 May 1432, Jan and his workshop had completed all twenty-four painted scenes which not only covered its interior, but also the exterior which was most prominent when the altarpiece was folded.
Examination of the panels shows that the techniques used by the two brothers, Hubert and Jan, appear indistinguishable, as might be expected from the same workshop. They painted in layers, varying their technique according to the nature of the passage. Dark and opaque passages are often made in a single layer, while more elaborate details such as fabrics and foliage are usually made from as many as seven layers. Different pigments and tones were used in layers much as they have been used in similar techniques ever since.
Even the grisaille passages on the outer aspects of the panels are carefully layered. Samples shown by Streeton, for example, may have dark modelling in carbon black or brown ochre over the chalk ground, then a thin layer of resin before a mixture of the same with yellow ochre and lead white, and further carbon black or brown ochre to deepen shadows.
Pigments identified in paint samples include cinnabar, ultramarine, malachite, azurite blue, and copper green including verdigris, which was a mainstay of the foliage passages in particular.
The van Eycks’ workshop bought in raw materials such as pigments, drying oil, diluent such as turpentine, and resins, and ground the oil and pigments to produce fresh supplies of the required paints on demand by its painters. As a centre of trade, Bruges would have had good supplies, with more sought-after pigments such as ultramarine being brought first overland then by sea to Venice, before being shipped round the Atlantic coast of Europe to reach the city of Bruges.
Since its dedication in 1432, the altarpiece has had a lot of history. It was first cleaned and ‘restored’ in 1550, which probably did more harm than good. In the summer of 1566 the cathedral was visited by rioting Calvinists, but the altarpiece was saved from destruction at their hands. This was the first time that it was dismantled, and it was dismantled again later that century, and again in 1794, when four central panels were taken for Napoleon’s new museum in the Louvre in Paris.
Although they were returned in 1816, by that time some of the outer panels had been pawned by the church, and those ended up being sold first to London and then to Berlin. Some of the panels which remained in Ghent were damaged by fire in 1822. During both the World Wars panels were removed to Germany, and in the latter years of the Second World War were stored in Austrian salt mines, which resulted in marked deterioration in their condition.
Extensive conservation programmes have now saved almost all of the remaining panels except one: the Just Judges had been stolen in 1934, and has never been recovered. The current version of that panel was painted by restorer (and sometime forger) Jef Van der Veken after the Second World War.
Streeton NLW (2013) Perspectives on the Painting Technique of Jan van Eyck, Beyond the Ghent Altarpiece, Archetype. ISBN 978 1 9049 8270 8.