How do museums figure out whether a painting is a forgery?

Museums use a combination of detective work and science to determine a painting's authenticity. This process usually involves three main pillars:

1. Provenance (The Paper Trail) Experts start by researching the painting’s history. They look for documentation that traces the work from the artist’s studio to the present day. This includes original receipts, exhibition catalogs, shipping records, and letters. If there is a "gap" in the history or if the paperwork seems inconsistent, it becomes a red flag.

2. Connoisseurship (The Eye of the Expert) Specialists who have studied a specific artist’s life and work closely examine the painting's style. They look for the artist's signature "hand"—their specific brushwork, how they handle light and shadow, and their typical use of color. If a painting’s brushwork lacks the fluidity or character of the artist, or if the composition doesn't match the artist’s known habits, it warrants further investigation.

3. Scientific Analysis (The Physical Evidence) When experts need objective proof, they turn to technology:

• Pigment Analysis: They take tiny samples of paint to identify the chemical composition of the pigments. If a painting supposedly from the 17th century contains a pigment that wasn't invented until the 19th century, it is a clear forgery.
• Radiography and Infrared Imaging: X-rays can reveal what is underneath the surface. Many artists changed their minds while painting, leaving "pentimenti" (visible ghost images of earlier versions). If a painting is too perfect or lacks these hidden changes, it may be a copy. Infrared reflectography can also reveal an artist’s original underdrawing (the sketch made before painting), which is very difficult for a forger to replicate convincingly.
• Carbon Dating: If the painting is on wood or canvas, scientists can date the material itself to ensure it is old enough to have been used by the artist.
• Microscopy: Examining the "craquelure" (the fine cracks in aging paint). Forgers often try to fake these cracks, but under a microscope, the patterns often look artificial rather than the result of natural drying and environmental stress over centuries.

Usually, it isn't one piece of evidence that condemns a painting, but a lack of evidence across all these areas. If the provenance is missing, the style feels "off," and the chemistry doesn't match the period, the museum will conclude the work is not authentic.