A Manual of Photographic Chemistry, Including the Practice of the Collodion Process

by T. Frederick Hardwich

The addition of the Nitrate of Silver is made in order to produce a portion of Hyposulphite of Silver in the bath; the presence of a Silver Salt having been found to modify the tint of the Positives, and to prevent their quickly turning yellow.

SECTION IV.

On the Fading of Photographic Prints.

For many years subsequent to the discovery of the process of Photographic Printing by Mr. Fox Talbot, it was not generally known that pictures so produced were easily susceptible of injury from various causes, and in particular from traces of the fixing-agent remaining in the paper. Hence, due care not being taken in the proper cleansing and preservation of the proofs, the majority of them faded.

This matter became at last one of such importance that the Council of the Photographic Society decided upon forming a Committee for the purpose of examining the subject. The Author was honoured by being placed upon this Committee, and the researches of which an abstract has been given in the previous Section, were undertaken at the request of the Society.

The present Section is intended to explain practically and in a concise manner the causes of the fading of Photographic Prints, and the precautions which should be taken to ensure their permanency. The chemistry of the subject having been fully explained in the last Section, it will suffice to refer the reader to its pages for more detailed information.

Historical evidence of the permanence of Photographs.—It is a point of interest to collect information as to the existence of old Photographs which have remained many years unchanged. There are numerous instances of Positives printed more than ten years ago, which have not perceptibly altered up to the present time. These prints are mostly on plain paper, Albumen not having come into use at so early a date. The general impression of practical operators however is, that fading has occurred less frequently since the introduction of Albuminized paper.

Positives printed by development on paper prepared by Talbot's method seem as a rule to have stood remarkably well, and instances of Talbotype Negatives having faded are rare.

Of the prints which have proved to be permanent, some are red or brown in colour, but many, being of a dark or purple shade, have evidently been toned, although not with Gold, the use of which was unknown to the earlier Photographers.