Double trouble: "The Virgin and Child with Two Angels" is attributed to both Verrocchio and Lorenzo di Credi
As evidenced by the popularity of crime fiction and television drama, ours is an age fascinated with forensic examination. There seems something uniquely satisfying about the stray hair or smear of powder residue that brings a murderer to justice, while the scientists who spend their time dispassionately reconstructing crimes of passion are modern-day heroes. It is therefore odd that Close Examination: Fakes, Mistakes and Discoveries at the National Gallery (until September 12) is the first major exhibition to study the impact of the gallery conservators who treat paintings with the same care with which their medical peers treat dead bodies.
In the absence of a provenance and strong documentary evidence, many a painting is a whodunit: not just who painted it but who commissioned it, who altered it, in some cases who or what it shows, in others who faked it. The stories that pictures tell exist below the surface every bit as much as on it. This exhibition surveys 40 paintings from the collection to explain the work of the National Gallery's Scientific Department and show how, since its foundation in 1934, it (and its equivalents around the world) has become increasingly important. The use of X-radiography, infra-red radiation, electron microscopy and chromatography not only reveal how a picture was made but also serve to remind us just how complicated a craft painting is.
Some techniques prove that a picture is not what it purports or is thought to be. In 1845, for example, the gallery bought A Man with a Skull, believing it to be by Holbein. It was not until 1993, when the panel on which it was painted underwent dendrochronological examination (using the pattern of tree rings to date the wood), that it was discovered that the oak had been cut after Holbein's death in 1554 and the portrait was reattributed to a minor Flemish artist, Michiel van Coxcie. Similarly, some pigments — cobalt blue, cadmium yellow, viridian — were invented in the 19th century. Their presence in seemingly older pictures, such as the 15th-century group portrait of members of the Montefeltro family acquired in 1923, can only mean that such pictures are at worst fakes and at best copies or pastiches (the best fakes have never been discovered and are still hanging on gallery walls as bona fide works by major painters).
Infra-red can reveal the artist's original underdrawing and changes he made to the initial composition — and consequently show the picture to be an autograph work. X-rays can show an artist's changes as he painted. Lorenzo Lotto's powerful Portrait of a Woman Inspired by Lucretia portrays a handsome woman in a striped dress standing next to a table and in front of a plain backdrop. Originally, however, the background was painted in blue and pink bands while the tablecloth was also striped. Lotto clearly decided that all these clashing stripes were too cacophonous only after he had painted them and he then covered them over.