Researchers simply shine black lights on paintings to help them view surface textures that are not otherwise visible in plain lighting. This low-tech method often is effective in identifying restoration work on paintings. Researchers rest film on the surface of a painting and photograph the work from underneath using an X-ray source. Mercury and lead, used by the old masters to mix red and white paint respectively, appear on the exposure. This method is productive in uncovering fakes because early forgers were interested only in surface effects.
Researchers warm a painting using a low-wattage light bulb.
Then they use the camera to record trace elements of carbon in the painting, which absorb the light's energy, and trace elements of calcium, which reflect it. During the Renaissance and Baroque periods, many artists used calcium-based glue and arabic gum to prepare their canvasses. They sketched underdrawings using pieces of charcoal or burnt animals bones, which consist of carbon. Van Miegroet's camera is able to pick up the trace elements because it makes visible the infrared spectrum. The aforementioned techniques may not be new to the art world but neither are they in widespread use and, except for ultraviolet research, they are still considered advanced methods of analysis.