I put a few paragraphs together for a local library about storage for some old film, plates and prints they are looking after. It's a very cursory overview but it may be useful to someone here...

Before storing I clean prints and negatives with an air blower (not compressed air just a bulb type blower) and a goat hair brush, goat hair brushes are very soft and won’t mark either prints or film. If the print or film is dirty with surface contaminants I will very gently wide down with PEC 12 Photographic Emulsion Cleaner and soft lint free PEC-Pads. With glass plates never try to clean the emulsion side unless you know your conservation materials and are absolutely sure of the process used to create the emulsion. If in doubt ask a conservator.

For prints/film in reasonable to good condition I use archival boxes and lay the items down separated by sheets of ‘silver safe’ photo paper, a neutral, unbuffered, 100% cotton rag. This is the best method I have found so far, principally because it is cheap and the ‘silver safe’ paper is unbuffered and extremely soft.

I use unbuffered paper with photographic prints and film because while the alkaline compounds used in buffered papers are not known to be detrimental to most types of photographic prints there is the possibility that compounds in the emulsion could react with buffered papers.

There is an alternative school of thought that says use buffered paper for everything as the risks are extremely low and after 10 years or so the alkaline buffer will be neutralised anyway.

As a result I hedge my bets and use unbuffered paper/mount board/envelopes etc. when it is in direct contact with the print, film or plate, where there is no direct contact I use buffered board, archive boxes etc. That way any material that is in direct contact with the print is neutral but the buffered board or box will help to reduce acid build up… possibly… in theory. There isn’t much consensus so if you are particularly concerned you will have to find your own way through the conflicting opinions and advice.

Either way make sure any materials used, particularly if in contact with the items to be stored had passed the Photographic Activity Test.

With damaged or fragile prints/film/plates (particularly with cracked/flaking emulsion) I pop the items into a polyester or polyethylene sleeve/envelope, then sandwich that between two pieces of buffered mount board to keep it flat and well protected, that then goes into a buffered archive box. The emulsion won’t stick to the polyethylene and any pieces of emulsion that do come adrift are contained within the sleeve so can be pieced back together for scanning. I prefer the polyethylene sleeves and envelopes, they aren’t as clear as the polyester but the material is softer and less likely to mark the print. Both are free of PVC so no gassing, yellowing or cracking over time.

Always wear gloves when working with delicate materials, cotton is usually fine but with flaking prints or deteriorating glass plates I prefer latex or nitrile gloves as the cotton can catch and pull away the emulsion if it’s lifting at the edges, latex or nitrile gloves also give a much better grip on glass plates.

Once all that’s done the prints or film should be kept in a reasonably cool (~15-20 ° C), relatively dry (~30-40% humidity) and dark place, though the most important thing is that the temperature and humidity are kept as stable as possible even if that’s outside of the ideal ranges.

Obviously if you have any alternative suggestions or corrections please respond, I am not a conservator so I'm not necessarily up to speed on the latest thinking.

Cheers,
Ady