Monday, February 13, 2012

Photo Preservation Guide Part 1: In the Darkroom

To understand preserving gelatin silver prints, one must understand the make-up of these materials. I will briefly explain the physical nature of paper and the chemistry used in creating these prints, and then explain the best practices in creating long-term archival prints. This is the first part of a three part series on preservation, this serving as the introduction to proactively create preservationally sound prints. Part two will focus on handling, exhibition, and environment. Part 3 of the series will explain the invasive conservation treatment of these prints.

Paper: Gelatin silver developing out paper has been around since prior to the last century, and has not changed dramatically. The fiber-based paper has a three-layer structure, with the paper being the support, a baryta layer made up of gelatin and barium sulfate to gloss over the paper fibers, and the final layer, which is a silver-halide emulsion. This is the layer where all the magic happens. This paper comes in all sorts of tones ranging from warm to cool, purplish, sepia, and neutral, as well as variations in surfaces and textures. Regardless of these choices, the main thing to remember is that the paper serves as the support for the silver that the image is created on. Resin-coated papers are also an option, but I do not recommend them for use in any sort of archival or long-lasting print. The polyethylene coating on both sides breaks down over time and eventually causes redux spots and other visibly damaging affects. Whereas there have been improvements in RC paper over the years, stick with fiber-based papers for longer lasting prints of high archival quality.

Chemistry: Photography is all about silver. However, the very noble silver alone is inactive, as it must form a bond with a halogen to be light sensitive. Silver bonds with either chlorine, bromine, or iodine to become silver halide, which is what creates the image. Curiously, the size of the silver halides determines the color so the different sizes of silver halides matter, a lot. Smaller, finer grains create a warm tone image, whereas a cool toned image has larger grains of silver halides. In early photographic images (think salted paper prints such as albumen and collodions), all have a reddish-brown hue because the silver halides were tiny. Today, of course, myriad choices of chemical combinations exist. This is just one little factor in the big game of photography fun. I continuously experiment with different films and developers, finding the perfect combinations for particular situations. Regardless of the size of the halides or what silver bonds with, for preservation purposes, proper water and fixing is most crucial.

A print with high silver content in the emulsion

Water: It may seem a bit jejune, but I think water is not talked about enough in photography. As a film photographer, there are so many choices to make - the type of camera to shoot with, what subject matter to shoot, what film, paper, and chemicals to use - but it can all be ruined if using impure water. Tap water can have all sorts of minerals and old pipes can leak rust; the best chemicals and most skillful methods of processing will not impact the finished product if the water is not pure. Beginning with developing the film to printing the image, distilled water is the best stuff to use. To achieve distilled water, regular untreated water is heated to the point of vaporizing, and since the boiling point of water is so low compared to the minerals it needs to be separated from, the water escapes leaving behind the sediment.

Use this water...
... not just any water you can find

So, to avoid deposits of impurities on the negatives and prints over time, all of which will eventually erode and attack what you thought was a well processed, long-lasting negative or print, please consider using distilled water. It will help achieve archival quality negatives and prints, which will outlast you and provide the world something stimulating to look at for decades and perhaps centuries to come.

Fixing: I don’t think fixing twice is so much an opposing argument as much as it is simply disregarded. In the early days of DOP’s (developing out papers), sending prints through two fixing solutions was common practice. The fixer washes out all of the non-developed silver halides, but if not done properly, over time, you will be able to watch your prints break down and die before you do. To properly fix and make an archival print, use the first fixer to wash out most of the undeveloped silver halides, agitating continuously, and the second to wash out what remains from the first fix. The reason is that while the first fix washes the print, it also creates contaminants, so a second fixer is needed to get the print squeaky clean. After a printing session, I always notice my first fixer has a darker, dirtier hue, whereas the second fix looks crystal clean. If the print is not fixed twice, the contaminants eventually penetrate the paper fibers and form mega-strong bonds that can never be washed out, and once oxidized will eventually break down the fibers of the print. So, if you want your prints to last longer than you do – fix twice, question its longevity and long-term preservation later.

Fix twice, hypo, and then put into the print washer for an hour

Toning: The black and white gelatin silver print, processed properly and stored appropriately, should last a few hundred years. However, many factors affect image permanence and for the most part, one does not make a print to store it away in a cool, dark environment never to be handled or displayed again. So after processing appropriately using distilled water and fixing twice, for another added layer of permanence and increased image stability, toning is a very good last step. A common toner to use that does not alter the image to much discernible degree is selenium. After properly fixing, the print should run through a hypo bath to clear the fixer off, and then a full washing. After washing, tone with a selenium toner that will then convert the silver to silver selenide which is a more stable compound than silver alone, and will be more resistant to atmospheric pollutants and oxidation. If the desired effect is to have no tonal change, the selenium should be diluted mildly and will yield strictly archival results. Ansel Adams was a big proponent of selenium toning and his prints today are a testament to time as they are still in excellent condition and probably will be for hundreds of years to come.

Read on in this mini series on Photo Preservation-
Part 2: Handling, Exhibiting, and Storing
Part 3: Handling Disasters and Professional Help



Bio:
Kate Contakos is Head of the Preservation Department at Stanford University, and was a founding member of Shutterclank! (film photography magazine). She shoots black and white film on her Leica, Mamiya, and Nikon, and spends lots of time in her custom built darkroom in her loft in San Francisco. She is currently addicted to Ilford’s MG Art cotton rag paper.

Find her here-
Twitter: @contakos
Flickr: http://www.flickr.com/photos/contakos/
Shutterclank!: http://www.shutterclank.com/


Further Reading and Resources

Books:
Adams, Ansel. The Print. Little, Brown and Company: Boston, 1983.

Issues in the Conservation of Photographs. Ed. Debra Hess Norris and Jennifer Jae Gutierrez. The Getty Conservation Institute: Los Angeles, 2010.

Lavedrine, Bertrand. A Guide to the Preventive Conservation of Photograph Collections. The Getty Conservation Institute: Los Angeles, 2003.

Rempel, Siegfried. The Care of Photographs. Nick Lyons Books: New York, 1987.


Web:
American Institute for Conservation Photographic Materials Group:
http://cool.conservation-us.org/coolaic/sg/pmg/index.html

Gawain Weaver’s Care and Identification of Photographs Workshops:
http://gawainweaver.com/

Image Permanence Institute:
https://www.imagepermanenceinstitute.org/

George Eastman House:
http://www.eastmanhouse.org/