Recently found about 150 photographs that my great grandfather took in France during the First World War when he was driving ambulances. I cannot post images in here but they are very silvery and I think they are some type of silver nitrate photography. Anyone have any advice on how best to preserve them? I wish I could post them in here.. they were an amazing find and he documented the complete destruction of Northern France where he was stationed.
I strongly recommend getting in touch with a local museum, they should have the preservation knowledge required to preserve your photos or at least put you onto someone that can.
This is more of a question for /archives but here is an answer:
Nitrate was used for film and is dangerous because it can burst into flames spontaneously. It also gives off toxic gasses when it burns. Archives that have nitrate film keep it in refrigerated storage, sometimes inside a blast-proof safe. Most Archives however will not store this type of film because of the danger. Insurance policies often will not cover you if you have it.
What you have though is almost certainly not nitrate film: you probably have gelatin silver prints. These are basically regular black-and-white prints, but yours may just have extra silvery qualities. This is a very common format for prints of this age.
To preserve them, the typical treatment would be:
Protect from abrasion by putting them in archival quality polyester sleeves. See Gaylord.com and look for photo sleeves for a source on these.
Protect them from being bent/crushed/etc by putting the sleeved photos into a rigid container. In a professional archives, you’d likely use archival folders inside an archival file box. For home use, you might prefer something else. Check Gaylord.com for options.
Protect from light by keeping the photos stored in a dark place; do not put the originals on display. (If you want to display them, scan the originals and make prints.)
Most important single thing you can do: keep them in a cool, not too humid environment. Keep them out of places like your basement or attic that might have high humidity or big temperature swings — these can bring on mold, crack the photos or just speed up the aging process. An air conditioned room is decent for home storage.
The originals are the most important, but to avoid more wear-and-tear on them and for easier access you could also make scans of all of them. The specs for that could be their own post, but basically you’ll want to make them at least 400 dpi.
Sources:
Mary Lynn Ritzenthaler & Diane L. Vogt-O'Connor. Photographs: Archival Care and Management. Society of American Archivists, 2006.
“Care of Photographs.” Northeast Document Conservation Center (NEDCC). https://www.nedcc.org/free-resources/preservation-leaflets/5.-photographs/5.3-care-of-photographs