I understand that seventeenth century artists signed their paintings, but it baffles me that so many paintings went unsigned. It's a bit of professional frustration because were sometimes asked to place and identify these.
I first thought this might have to do with a painter's studio/atelier being responsible and so couldn't have the 'master's hand' on it. But a lot of 'smaller' painters have missing signatures on sometimes very well done pieces - meaning it isn't a case of quality either.
Then there is the sudden shift where everyone is signing everything and the signature itself becomes more important than the painting itself.
I was also wondering, as an optional question, about the use of red paint to mark the signature, whether or not there is another rule of use here?
Thank you in advance.
This is a bit of a complicated question because the answer doesn't quite break down according to time so much as "is there some compelling reason for anyone to care about who made a specific work". Accordingly, we can expect the answer to vary according to time, place and culture. The oldest examples I know of, interestingly, are non-western. We know of several Sui and Tang dynasty paintings which were known to be by specific individual artists although the question of signature is complicated by the fact that most of these survive only in later copies. More excitingly, the decipherment of Mayan hieroglyphics has revealed that a number of Late Classic Mayan vessels were signed and in a few cases we have even been able to reconstruct the corpa of various artists. In the Western Middle Ages, it is of interest to note that you do have some signed artworks, but that many of these are large public commissions with extremely visible signatures and even into the early modern period artists could be wildly inconsistent about signing their own work. To the degree we can make useful generalizations, artist signature's start happening when the artist A) has a specific reason to publicize his involvement in a particular work whether to publicize his involvment in a major civic project, to claim an artwork as his own in a specific exchange system, or because he or she knows people will care about who made the artwork they are buying and B) is of high enough social standing for anyone to care about this. A "smaller' painter, for instance, might not have much reason to sign their work and a major painter doing basically minor work might likewise lack reason to sign their work, wherehas a highly trained and esteemed scribe-painter of noble birth has every reason to stake a claim to a well-done piece of work.