One of two Bust of Patroclus negatives to be superimposed with Schaaf number 5584 for printing in register. The writing on the envelope that held the two negatives together has transferred onto the wax of the negatives.
Negatives were sometimes combined to increase the density in printing - by careful alignment the dark areas could be made to reinforce each other. In addition, negatives may have been combined to expand the tonal range of the print but as Schaaf number 5584 and 5585 match closely, it is more likely that they would have been combined for the former reason.
Talbot describes his technique for generating two negatives to print in register, and his reason for doing it in a letter to Claudet.
"At the moment, I am conducting an experiment which I hope will have the positive result of increasing the contrast between white & black areas on the negative & at the same time of neutralising the defects of the paper. I make a positive through two negatives at once. I copy a positive in order to obtain the second negative. As the paper is cut in advance, in such a way as to have a perfect right angle on one side, it is then easy to match the three sheets. I do not know if this method will be easy to carry out in practice, but I am sure that there will be a greater intensity in the white & blacks. Then, since no two sheets of paper have the same defects, they will be less evident on the copy. The lack of light has prevented me from repeating this experiment, which produced the expected result on the first attempt. It took me three days to copy it & I had not taken precise enough measurements to make the two images match, with the result that my portrait was not very clear but the white & black areas were much purer than in an ordinary copy. This first idea may lead me to other ideas of a similar nature."