Materials and techniques for retouching glass plate photographic negatives in the beginning of the 20th century

In the early 20th century, photography is already established in society and within the reach of many. Photography studios exist in cities and traveling photographers take photography to the rest of the population. Like today, at that time, photography was divided into key sectors, among them, photojournalism, portrait, artistic photography. Like today, not short from controversial, in particular in the sector of portraits, photography was commonly manipulated, better said retouched, for several reasons: correction of photographic flaws, to improve or modify the composition, contrasts etc., or as an artistic expression. How was photography being retouched in the early 20th century? Today there are generally available known digital tools. A hundred years ago, the retouching was done by hand, by the photographer, or by specific professionals that don’t distance themselves, in technical demand, of the arts of drawing and painting. But the retouching was invisible in the final object, because the changes were done on the negative. Contemporary books, in the form of manuals, are a window to the past telling us about the techniques and materials used. Existing archive collections of photographic glass plate negatives are testimony to the expertise of photographers and the practical use of those books. The present work will show examples of tools and materials used for retouching of photographic glass plate negatives, taking as an example a portrait collection at the Photographic Archive of Lisbon.