Think about the last time you walked through a museum. So many beautiful works of art to admire! But have you ever wondered if those artworks are actually authentic? Were they really done by the famous artists to whom they were attributed? Or are they modern-day forgeries? Let’s see if there’s a way to tell if an artwork is fake or real and see how to identify fake paintings using science.
Different scientific methods provide different kinds of information about the object we analyze and they can be used to detect if a painting is fake or real. These scientific methods can be clustered into three categories depending on the type of information they can provide. The three categories are: visual (or imaging), elemental (or structural), and dating techniques.
Visual (or imaging) techniques
Visual techniques consist of scientific methods that can provide some sort of visual cues or images of the painting. These can be used to analyze that painting and search for details that you would expect to appear, or not, in that particular painting.
Some of these techniques can be used to image the underlayers of a painting. Depending on which area of the electromagnetic spectrum we employ, we can access some, or all, layers of a painting.
If we use infrared radiation in a technique called infrared reflectography, we can obtain images of the sketch layer. Through the analysis of the sketch layer, we can see if there are any differences between what the sketch and the final painting look like. This doesn’t necessarily tell if the painting is a forgery, it could simply mean that the artist changed his or her mind while creating the painting. But a significant difference between the sketch and the final product is something that should be further investigated.
In X-radiography, we make use of X-rays to obtain an image that contains information about different layers of the painting. Sometimes forgers reuse old canvas to paint their forgeries to make them look older. If the X-radiography reveals a newer painting beneath what is sold as an older painting, then that clearly indicates a forgery.
Neutron activation autoradiography
In neutron activation autoradiography, we use neutrons to irradiate the painting. We then obtain images showing the distribution of pigments containing the activated radioactive elements from the painting layers. If the autoradiography reveals the presence of newer pigments in the painting, pigments that were not available at the time when the painting was made, that could be an indication of forgery.
We can use a stereo microscope to carefully examine the surface of the painting. One indication of forgery could be found in the craquelure pattern—that is, the patterns of cracking observed on the surface of the painting, which can be due to aging. There are different craquelure morphology styles observed in paintings from different periods and countries. A pattern that is inconsistent with the expected pattern of that painting could indicate a forgery.
The painting surface can also be inspected under UV light using a method called ultraviolet fluorescence. When UV light is shone on the painting’s surface, it will induce visible fluorescence in some of the painting’s materials. This fluorescence is visible to the human eye, and it provides an indication of restoration or overpaints, and while it could simply be an indication of restoration, it could also point towards forgery.
Elemental (or structural) techniques
The elemental, or structural techniques, are scientific methods that provide information about which chemical elements are present in the painting. They can also provide information about the presence of certain chemical functional groups, and even more complex structural information. Detecting certain elements in a painting that should not be there is a clue that could be used to identify fake paintings.
To identify the elements that are present in the painting, we can use X-ray fluorescence (or XRF) and proton-induced X-ray emission (or PIXE). For this kind of analysis, we send a beam of either X-rays (in XRF) or high-energy protons (in PIXE) to a spot on the painting that we want to analyze. In both cases, X-rays are emitted as a response, and by analyzing the energy of those X-rays, we can identify the elements that are present in the painting.
Once we know which elements are present in the painting, we can then identify the pigments used in creating the painting. Identifying certain pigments that were not available at the time when the painting was supposedly made could be an indication that the painting is a forgery.
Chemical functional group identification
We can detect the presence of certain chemical groups and molecular fragments by using infrared (IR) spectroscopy and Raman spectroscopy, as well as mass spectrometry. All of these methods are helpful in identifying the pigments, however, mass spectrometry is an invasive technique. That means that we have to remove a bit of a sample from the painting in order to analyze it. Ideally, especially if the painting is authentic, we’d prefer to use non-invasive techniques.
All of these methods complement each other, and the more information we can gather about the different chemical components of the pigments and binders, the more confident we can be in our verdict of whether the painting is fake or real.
Dating techniques are methods that can reveal the age, or information about the aging, of the painting. The age of the painting can be used to identify fake paintings.
To find out the age of an object, we can use radiometric dating. This method makes use of the radioactive decay of certain elements in the sample. Probably the most commonly heard of is radiocarbon dating. Knowing how much carbon-14 we have in a sample and the isotope’s half-life, that is the time it takes for the initial amount of carbon-14 in the sample to decay to half of that amount, we can use this information to find the age of the painting sample we’re measuring.
Another dating method is dendrochronology or tree ring dating. While this method can provide accurate chronology, it can only be applied to wooden objects. For paintings, this means we can only apply dendrochronology to paintings done on wood panels. We can use the tree ring information—the ring number and patterns—from the wooden panel to identify the age of that panel.
If either of these dating methods determines that the painting is newer than its attributed date, that’s yet another indication that we’re dealing with a forgery. However, if the date matches, that’s not an indication of authenticity. That’s why it’s always best to combine the information obtained from different scientific methods before giving a final verdict.
Mobile nuclear magnetic resonance
Mobile nuclear magnetic resonance uses radiofrequency pulses to irradiate a sample in a magnetic field. It is a non-invasive technique that can be used to analyze painting stratigraphy and the aging of paint. This is important because forgers like to artificially age their paintings to make them look old to appear authentic. So then the chemical signature of artificial aging could also be used to identify fake paintings.
Provenance is not a scientific method, but it is one method that has been used extensively in assessing the authenticity of a painting.
Provenance uses historical records of ownership of the painting from the time it was created up until its current ownership. Unfortunately, provenance can also be forged, and some of the famous art forgers managed to get away with their forger careers for a long time because they were so good at forging not only the paintings but also the historical records.
Therefore, it’s better to rely on clear scientific evidence when identifying forgeries. And the more information we can gather from different scientific methods, the more accurate our conclusion will be.