Uncovering modern paint forgeries by radiocarbon dating

Art forgeries have existed since antiquity, but with the recent rapidly expanding commercialization of art, the approach to art authentication has demanded increasingly sophisticated detection schemes. So far, the most conclusive criterion in the field of counterfeit detection is the scientific proof of material anachronisms. The establishment of the earliest possible date of realization of a painting, called the terminus post quem, is based on the comparison of materials present in an artwork with information on their earliest date of discovery or production. This approach provides relative age information only and thus may fail in proving a forgery. Radiocarbon (¹⁴C) dating is an attractive alternative, as it delivers absolute ages with a definite time frame for the materials used. The method, however, is invasive and in its early days required sampling tens of grams of material. With the advent of accelerator mass spectrometry (AMS) and further development of gas ion sources (GIS), a reduction of sample size down to microgram amounts of carbon became possible, opening the possibility to date individual paint layers in artworks. Here we discuss two microsamples taken from an artwork carrying the date of 1866: a canvas fiber and a paint chip (<200 µg), each delivering a different radiocarbon response. This discrepancy uncovers the specific strategy of the forger: Dating of the organic binder delivers clear evidence of a post-1950 creation on reused canvas. This microscale ¹⁴C analysis technique is a powerful method to reveal technically complex forgery cases with hard facts at a minimal sampling impact.