JAIC 1999, Volume 38, Number 2, Article 2 (pp. 124 to 143)
JAIC online
Journal of the American Institute for Conservation
JAIC 1999, Volume 38, Number 2, Article 2 (pp. 124 to 143)

DIFFERENCES IN IMAGE TONALITY PRODUCED BY DIFFERENT TONING PROTOCOLS FOR MATTE COLLODION PHOTOGRAPHS

SYLVIE PENICHON



7 PROCESSING, MOUNTING, AND FINISHING

The traditional sequence of baths for processing gelatin or collodio-chloride papers after exposure in the printing frame was: washing, toning, fixing, and washing, although toning and fixing would sometimes be done in one combined bath. A clear water bath was required before toning to eliminate the excess of soluble silver salts in the emulsion. To compensate for the weakening of image with the dissolution of silver salts that occurred during washing, the print had to be overprinted. Because prints dry up “darker and bluer” (Wallace 1888, 164) than when seen in the toning bath, the correct tone had to be checked by viewing the print with transmitted light during processing. A hardening bath made of chromium alum and formaldehyde was sometimes used between toning and fixing. It was to prevent excessive swelling and softening of the gelatin contained in the baryta layer that would result in the collodion film peeling right off the paper (Baker 1904).

The collodion prints were usually mounted when still damp. Spotting was done with either gelatin, gum, or albumen mixed with some pigment (Woodbury [1898] 1979, 116). If a glossy surface was desired, the print was burnished or squeegeed face down against a sheet of glass and allowed to dry in this position. Before mass production of matte collodion papers, matte surfaces were obtained with the same technique on ground glass. Woodbury describes another alternative:

Another method of obtaining a matte surface is by drying the prints with their natural surface, pinning them to a flat board and rubbing the surface well all over with some fine pumice powder and a piece of flannel. The powder must be very fine and absolutely free from grit (1893, 90).

Later, a matte surface was obtained by using a coarse layer of baryta under the emulsion (Bentzen 1926). Rice starch was sometimes added to the baryta to achieve a matte surface (Wentzel 1960).


Copyright 1999 American Institute for Conservation of Historic and Artistic Works