How Paintings Are Authenticated
Authentication is three separate investigations that have to agree: the documentary record, the physical object, and the eye. Any one of them alone proves very little.
In short
- Authentication is a convergence of evidence, not a single test.
- Science can usually disprove; it very rarely proves.
- A picture with impeccable materials and no history is still a problem.
- The authority that matters is whoever controls the catalogue raisonne.
Three investigations, not one
An authentication runs on three tracks. The documentary track asks what the paper record says: inventories, wills, sale catalogues, exhibition records, photographs. The physical track asks what the object is made of and when those materials became available. The connoisseurial track asks whether the picture behaves like the artist's other work.
None of the three is sufficient. A perfect provenance can be attached to the wrong picture. Perfect materials can be assembled by a competent forger working on a period canvas. And the eye, however good, is one person's opinion until it is corroborated.
What science can and cannot do
Technical analysis is asymmetric, and this is the single most misunderstood thing about it. It is extremely good at exclusion and weak at confirmation. A pigment that was not manufactured until 1920 in a picture said to be from 1650 settles the matter immediately. The same picture containing only period-appropriate pigments has been shown to be consistent with the claim, which is a much smaller statement.
Dendrochronology can date a panel's tree and give a plausible earliest date for the painting. Infrared reflectography can reveal underdrawing and show whether the composition was worked out or copied. X-radiography can show reuse and pentimenti. Each narrows the field. None of them signs the picture.
Why the eye still decides
In practice most attributions still turn on connoisseurship, because the physical evidence is usually consistent with several candidates. A competent workshop assistant used the same pigments, the same panels and the same underdrawing habits as the master.
This is uncomfortable and it is why the field defends its methods so vigorously. What separates disciplined connoisseurship from taste is that it is falsifiable in principle: it makes claims about specific passages, and those claims can be tested against securely documented works.
Who actually decides
For most artists with a serious market, the effective authority is whoever maintains the catalogue raisonne. Inclusion is worth money; exclusion is close to fatal. Several authentication boards for twentieth-century artists have been dissolved after litigation, which has pushed the decision back onto individual scholars who are now, understandably, more reluctant to give written opinions.
The practical consequence for a buyer is that the question is not only 'is it right' but 'who will say so in writing, and will that opinion still be respected in ten years'.
Questions
Almost never. Tests establish that materials and structure are consistent with the claimed date and artist. Consistency is not proof; it is the absence of a specific disproof.
An anachronistic material. A pigment, ground, canvas weave or fixative that did not exist at the claimed date ends the discussion, subject only to questions about later restoration.
Litigation. Boards issuing negative opinions have been sued by owners, and the cost of defending those suits exceeded the benefit of running the board.