Hi Tati,
You and I both were probably (unsuccessfully) madly Googling away in both English and French for horsehair cardboard!!!
Perhaps the horsehair didn't actually refer to the cardboard ...
Let's hope a person with French photo framing interests of the time turns up!
Perhaps 'crin' didn't refer to 'carton' ... But to 'noir' i.e. black horsehair!!!
Perhaps the photo (when Alan manages to post it) will give some clues.
JAP
