Fun with Photo Negatives
During my internship yesterday I decided to take a quick break to check out some photo negatives in one of the collections stored near my work station (admittedly, I needed some time away from Excel).
While I tend to write more about all things outdoors on this site, it also doubles as a place where I want to share some of my interests related to being an archivist (complete with cool photos). My major interest within the field of archives are, as to be expected, collections related to the outdoors, whether that be historic maps, documents related to environmental research, or outdoor recreation (i.e these John Muir Letters). However, I also just like old things in general, especially photographic negatives. They have really interesting preservation requirements that change throughout history, requiring archivists to be aware of photographic technology and how best to treat it in an archival environment.
For example, the (slightly blurry) photo below and left features a nitrate negative, which is composed of cellulose nitrate (which is a made up of cellulose, which is found in plant cell walls, which is treated with nitric + sulphuric acid) and an emulsion layer to create a transparent and flexible base, and in fact, it was the first commercial base of its kind. Unfortunately it’s extremely flammable and thus presents a serious danger with improper storage in warm areas. Consequently, it is ideally kept in cold storage up to 37ºF in low relative humidity (20-30%). Failure to do so can result in these negatives degrading over time, especially when exposed to warm and moist conditions. Fortunately, cellulose nitrate was really only used up until the 1950’s, which is useful to know when identifying film negatives.
Another popular film base, cellulose acetate, was developed later to replace cellulose nitrate (starting in around 1925 and still available today) as a safer base, which is often labeled as “Safety Film” on the negatives themselves (though, don’t be fooled, these can sometimes be made of polyester too). Unfortunately, these also suffer from their own host of deterioration issues, most notably “vinegar syndrome” which comes along with shrinkage and a very notice vinegar smell. When I took the photo below out of it’s acid-free envelope I was immediately aware of an intense vinegar smell, which has clearly coincided with some intense shrinkage and warping in the emulsion layer (probably due to low humidity).
Fortunately, when put on a light table, you can still somewhat see the image on the negative (see photo), but this will over time continue to deteriorate if it’s not put into cold storage (36-45ºF, depending on your humidity).
If you’re interested in learning more about how to preserve some of your film negatives (and photos too), here are a few fun links:
Image Permanence Institute Media Storage Quick Reference, 2nd Edition by Peter Z. Adelstein (might be a bit technical in places, but there are some nice little quick reference boxes!)
Film Structure Information from Kodak
And there are many more!
(copyright: negatives pictured here are not reproducible, only with permission).