Hyper high resolution photography allows us to project a photo of a small detail in a painting to be 3 ft or 1 m tall or wide. This technology gives us the opportunity to examine every square inch or square cm as if we were using a microscope.
Ultraviolet light used in the dark reveals every repair and every touch up that has ever been done.
X-ray technology allows us to see below the epidermis and to view what may lie hidden underneath, such as pedimenti, or a previous composition, or a signature.
Pigment analysis lets us check if the paint used was available to Renoir and whether it is the type of paint he was using.
Carbon dating tells us how old the canvas or the paper or the wood is.
Solidified fingerprints captured when the paint was soft can be photographed and compared to other fingerprints in Renoir paintings.
DNA could be extracted from a Renoir hair if one was discovered embedded in the paint.
The list of what science, technology and forensic studies can do to help us authenticate, keeps expanding. We are now looking at applying Artificial Intelligence in the authentication process.
We use every method, every approach, every technology that can help us demonstrate if a Renoir is indeed a Renoir.