Radiochemical technique and Art Forgeries

Han van Meegeren was infamous for his abilities to forge paintings during the early 20th century. He was captured by the Dutch police in 1945 and was charged with selling a painting by Dutch artist Jan Vermeer to Nazi Germany. If convicted he would be sentenced to death. Meegeren argued that the painting he had sold to the Nazi was only a forgery and admitted to forging other paintings by Vermeers as well. To prove this claim, he created another forgery of one of Vermeer’s painting. Thus he was found innocent of collaborating with the Nazi but was found guilty of forgery, a lesser crime. It was not until two decades later that scientists could use the radiochemical technique to verify that one of the paintings called “Christ and His Disciples at Emmaus” was indeed forged by the hands of Meegeren. The painting by Vermeer would be painted around the middle of 17th century.

Artists have used white lead (lead hydroxyl carbonate) for centuries and the lead came from an ore called galena. The ore containing uranium is in radioactive equilibrium with its daughter products, two of which are 210Pb and 226Ra. The radioactive equilibrium is affected by the chemical removal of lead from the ore. During extraction 226Ra is removed while 210Pb is not removed and is found in white lead with another stable isotope form, 206Pb. Since 226Ra is removed, 210Pb begins to break down in order to achieve equilibrium with the miniscule quantity of 226Ra that’s left in the white lead. Researchers assumed that it would take 270 years to establish this equilibrium if the ratio of 226Ra to lead 210Pb is 100:1. Armed with this information, the scientists were able to determine that the painting was not painted by Vermeer because the equilibrium would have been achieved by 1960. They however, found that the painting was less than 100 years old! Thus, they concluded that it was indeed a forgery.