Fraud is an ongoing issue that’s plagued the art industry, and appears to become more frequent with each passing year. While there are standard procedures to help determine whether artwork is genuine, forgers still find ways to bypass these methods.

In modern times, art gatherers have turned to science for help in determining what is and isn’t authentic. The colors and designs depicted in a piece of artwork are seen through the visible spectrum of light, however an art display can be viewed differently and reveal unforeseen details when seen through parts of the spectrum we can’t see with the naked eye.

To understand how the electromagnetic spectrum can be applied to the process of artwork authentication, it helps to understand how the spectrum is composed. The electromagnetic spectrum’s range features high-frequency gamma rays and low-frequency radiation on both its ends.

Let’s keep in mind that color frequencies in the visible spectrum range from blue (800 terahertz) to red (400 terahertz). Frequencies below the visible spectrum like near and mid-infrared range from 30-300 terahertz, with far-infrared having up to one terahertz unit. Further down the spectrum, there are microwaves and radio waves, whose frequencies range from gigahertz to kilohertz. Around this point of the spectrum, the terahertz part falls between the radio and visible parts, essentially right in between electronics and photonics.

An image can appear completely differently when viewed in the terahertz range. Water for example, is perfectly transparent in the visible light spectrum, however, isn’t in terahertz light. Black plastic can’t be penetrated by visible light, but can be transmittable by terahertz radiation.

When viewed by the naked eye, two same-colored objects could transmit terahertz radiation differently from each other, which would make their signals distinguishable. It’s these qualities that can distinguish paint and pigments from each other, which is something terahertz spectroscopy can do.

Now insert any piece of artwork being put into question.

Despite how protective art holders are of their collections, terahertz spectroscopy can conduct an efficient examination without making any physical contact with the canvas. While most authenticity analysis processes require a small material sample, terahertz spectroscopy is simply applied by shining onto the painting, during which the transmitting radiation is measured. A painting will show no signs of damage or sabotage if the terahertz radiation has low energy and density.

One of the ways this process can determine artwork is fraudulent is by detecting something like the quinacridone pigment, which is artificial material first developed in 1935. This would affirm the painting was made no earlier than that date, and could refute claims that a piece was made by artists like Leonardo da Vinci, Vincent van Gogh, or Claude Monet (all of whom died years before 1935).

Other methods like analyzing artwork by sophisticated quantitative measurements of the visible spectrum can also be applied onto pieces like paintings. Light lying above the blue end visible spectrum can also be used to evaluate artwork like paintings. Ultraviolet (UV) photons, for example, have more energy than visible photons in this part of the spectrum, and can put energy into re-radiated material as visible photons.

The processes of fluorescence and UV-fluorescence are the established tools in art conservation as a result. X-rays can also be used to examine artwork, since this end of the spectrum was used at the Australian Synchrotron to uncover hidden layers in works by Edgar Degas and Arthur Streeton.