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Conservation Notes: 19th Century printing out processes

February 10th, 2017

2013/368. Julia Margaret Cameron. Beatrice, 1866, Albumen print

Photography as an art form has a rich history that has seen the invention of many photographic processes and prints. This is the second article in a series written to give AGO patrons a greater depth of understanding about the various photographic processes in the collection. You can read the previous article at here.

Readers older than a certain age will remember sending rolls of film to be developed and printed.  You’d shoot a roll of film, take it to the local film lab, and wait.  After a few days, you could pick up your processed negatives and prints.  Prior to the invention of digital photography (this post deals exclusively with pre-digital photography), most photographs were produced as prints.  A photographer would capture an image on film, the film would be processed into negatives, and then a positive print would be produced.  Both the negative and the print would have been ‘developed’ – a chemical process that transforms a latent (invisible) image into a stable one that can be viewed and handled safely.   Historically, that wasn’t always the case.  Over the history of photography, a wide variety of chemical processes have been used to create prints.  This series of articles will explore some of the processes and their resulting prints.

96/1249, Linnaeus Tripe, Amerapoora. Maha-Too-Lo-Bounghian Kyoung, 1855, hand-coloured albumen printing out print, printed from a paper negative

The processes discussed in this article are “printing out processes” (POP).  This means that the image actually appears on the paper without any chemical ‘development’.  Once light is exposed to the paper, the image simply starts to materialize on its own. Left on its own, the image would keep getting darker and darker until the whole print was black.  To avoid this, the image is “fixed” in a thiosulfate, or “fixer”, solution.  This halts the printing out process and produces a relatively stable image on paper.

POPs were invented in the 1840s and represented a major advancement in photographic technology. Prior to POPs, every photograph was unique. The photograph that was exposed in the camera was the only copy. For instance, the Salted Paper print, created a negative that could be used to print multiple copies of the same photograph. 

Salted paper prints

Introduced in 1840 by William Henry Fox Talbot, salted paper prints were among the first photographs to be produced wherein multiple copies were possible. It is a relatively simple process by which writing paper is soaked in a photolytic silver sensitizing solution and then exposed in a printing frame, in contact with the negative (hence the term “contact print”). Then it is exposed to strong sunlight until the image appears.  The paper is then transferred to a thiosulfate solution to “fix” the image, without which the image will quickly turn completely dark.  The print is then washed to remove as much of the residual chemicals as possible.

Salted paper prints are readily identifiable by the lack of binder, or coating. The image exists in the actual fibres of the paper support. This can make the image appear rather un-sharp in some cases.  Also, salted paper prints are very susceptible to fading and discolouration. As seen in the corners of this photograph of Dr. George Cook.

2014/562, David Octavius HILL, Dr. George Cook, c.1843, salted POP

Albumen prints

Albumen prints are an evolution of the salted paper print.  Introduced by Louis Desire Blanquart Evrard in 1850, the process uses the same chemistry, but with the addition of a coating of albumen, from hens’ eggs.  The coating covers the surface and prevents the chemistry from soaking into the paper, allowing for a more resilient image because the image silver is protected by the albumen coating and not just the paper fibres, such as in the salted paper print.  The illustration below depicts the layers of an albumen print with the image containing binder layer on top of the paper substrate.

One way to identify albumen prints is the presence of cracking and yellowing of the albumen binder.  The cracking is due to the fact that the paper support and the albumen sizing swell and shrink at different rates as the humidity fluctuates in the print’s environment.  The yellowing is a result of the “Maillard” reaction, where sugars present in albumen react with the egg proteins to form yellowish-brown products.  In an attempt to counter-act the discolouration resulting from this reaction, tinted albumen papers where produced in purple, pink, blue and green hues.

If you look in the bottom right hand corner of the print of Chaudière Falls, you can see in-touching that has been done by the artist to hide a flaw in the print. The in-touching would have originally been the same tone as the background image and is an indication of how much the print has yellowed and faded over the years.

2012/126, William NOTMAN, [Chaudière Falls, Ottawa, ON], c.1866, albumen POP

Collodion prints

Collodion prints are similar to Ambrotypes and Tintypes [link to “a case for all photos” post] in that they have a collodion binder, however Collodion prints are on paper, whereas Ambrotypes are on glass and Tintypes are on metal.  There is no one clear inventor of the collodion on paper process: many chemists and photographers contributed to the process.  It was available in the 1860s but did not gain popularity until the late 1880s.  Early collodion on paper photographs had to be made on heavily sized paper, so that the collodion binder would not soak into the paper.  With the advent of the baryta layer, introduced in 1884, the process became much more obtainable.  The illustration below depicts the layers of a collodion (or gelatine) print, with the baryta layer sandwiched between the image containing layer and the paper substrate.

Due to their strong tendency to curl, collodion photographs were commonly mounted to card stock.  They can be found with glossy or matte surfaces and can be identified by their lack of fading or discolouration, especially around the perimeter.  There will also be the possible presence of small scratches that expose the white baryta layer (Collodion binder is very thin and therefore is scratched away very easily).  The baryta layer, introduced in 1884 in Germany, is made primarily of white barium sulfate and serves to create a smooth, white surface for the collodion layer to rest upon.  Earlier processes, such as albumen and salted paper prints, have only the binder and paper layers, giving the images a less sharp appearance.

 

2007/302, Unknown French, Street Occupations: Newspaper Vendor, 1907, Collodion POP

 Silver Gelatine Printing-Out-Prints

In 1871 Richard Leach Maddox revolutionized photography with the introduction of Silver Gelatine Printing-Out-Paper. In as soon as 1874 commercially made gelatine-halide (chloride and bromide) papers became available, making photography available to a wider audience.  For the first time, a photographer could purchase boxes of ready-made sensitized gelatine halide paper.  Not only was much of the work done for you, the papers were also much more sensitive to light than earlier processes.  That meant prints could be made utilizing lower light levels, and were therefore called “gas-light” papers, referring to the relatively dim lanterns that provided the illumination for exposure.  With the exception of very early silver gelatin POP and some later types of technical and copy POP, almost all other POP papers were produced using a baryta-coated paper stock.
The color of the silver image of a POP silver chloride photograph usually ranges from light yellow-brown to red and darker brown.  The color of silver bromide POP images is usually cooler and grayer. These visual clues hold only for POP photographs that have not been toned. Most silver gelatin POP photographs were gold toned.  Toning usually shifts the image color to red-violet or dark black-violet.  Silver gelatin POP was produced in several surface-texture qualities. At first only glossy or matte surfaces were available, but after the turn of the twentieth century the number of available textures increased.

2008/1144.1-.48, J.C.M. HAYWARD, Pulp in Wire Mats, 1912, gelatine silver POP

Salted paper, albumen, collodion and early gelatine printing out prints were a major innovation in photography in that, with the use of negatives, multiple copies of the same image could be made.  While they were contact prints only, meaning the negative had to be in contact with the print during exposure, POPs made photography more accessible to the amateur photographer.  Photographs on paper such as the Platinotype, Carbon, Woodburytype, and Cyanotype (Non-silver and pigment based) will be discussed at another time.

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