The Wet Collodion Process

Thomas Rodger

Below are some extracts from Thomas Rodger's paper On Collodion Calotype,
 read to the Royal Scottish Society of Arts in Edinburgh in February 1854.

1

Background

A difficult process ...

"In the practice of a new and difficult process, the success of which depends on a number of minute details, which, though they admit of variation, require very nice adjustment, there is much room for ingenuity and improvement."

"Hence, it is of great importance to simplify the process and render it more certain in its results.  My aim will be to detail shortly that process as practised by myself with considerable success and certainty ... without reference to the modes adopted by others."

"The adjustment of the chemical materials to each other is of such importance  that the greatest accuracy is required in their preparation.  All the manipulations of the process also require the greatest care.

Calotype v. Collodion

"All the former modes of calotyping have been superseded by the process of collodion on glass plates."

"Wonderful and beautiful as the pictures by the paper process were considered a short time ago, those by the glass plate process have quite outstripped them, for rapidity of execution, minuteness of detail , for expression and beauty of finish.  It is therefore to this process alone that I will confine my remarks."

"By far the most important and difficult part of this process is the preparation of the chemical  materials to be employed and the nice adjustment of these one to another.  In this part of the process, there are a great variety of opinions, but most individuals who have practised this art for any length of time, have, after many experiments, adopted certain methods which they have found to be most successful."

Printing

"We will now go on to the process of transferring to paper impressions from the negative pictures, which, although decidedly more simple and more easily conducted than the previous process, is, nevertheless, often attended with very unsatisfactory results."