Film Archiving and Long-term Preservation: Acid-Free Film Sleeves (Print File), Humidity and Temperature in Moisture-Proof Boxes, and Rescue of Moldy Film

1. The Life-or-Death Line of "Acid-Free" Materials for Film Protection

After developing and drying, negatives must never be stored long-term in ordinary plastic bags or low-quality PVC bags provided by the photo lab!

• PVC Plastic's Volatile Killer: Cheap PVC plastic bags contain large amounts of phthalate plasticizers which, under high temperature and humidity, slowly decompose and release corrosive hydrochloric acid gas (HCl). After a few years, the plastic bag can become oily and sticky, chemically fusing with the gelatin emulsion layer of the film. When peeled apart, the emulsion crumbles and flakes off!
• The Only Compliant Material: Archival-Grade Polyethylene (PE) or Polypropylene (PP): You must choose professional acid-free sheet film sleeves that have passed the Photographic Activity Test (PAT), such as Print File 35-7B or 120-4B from the United States. Chemically inert, they will not react with gelatin even after a century.

2. Four Standard Procedures for Archival Film Management

1. Cutting Standards: 135 film should be cut evenly into sets of 6 frames each (Print File 35-7B single pages can hold exactly 7 sets, totaling 42 frames, perfectly accommodating a full roll of 36 frames plus the leader); 120 film in 6x6 format should be cut into sets of 3 frames.
2. Wear Powder-Free Cotton Gloves at All Times: Human fingers secrete oils and sweat containing trace amounts of sodium chloride and lactic acid. Handling negatives bare-handed leaves fingerprint oil marks on the base which can develop dense, snowflake-like fungal mold over the years.
3. Special Sealed Dustproof Sheet Holders: Place the film sleeves into acid-free sheet archival boxes with fully sealed edges, completely isolating from air, dust, and direct light.
4. Stable Temperature and Humidity Standards:
   • Relative Humidity (RH): Strictly maintain 35% to 45% (Humidity above 60% can cause mold outbreaks; below 30%, film becomes excessively dehydrated, brittle, and prone to cracking and curling);
   • Temperature: Below 20°C, avoid light and ensure ventilation.

3. Guidelines for Rescuing Moldy Film

If old negatives have developed spiderweb-like mold colonies due to moisture:

• Never Rinse Directly with Water: The gelatin emulsion is extremely soft and fragile when damp; a brief dip in tap water or gentle rubbing will cause the emulsion to fall apart and melt!
• Professional Anhydrous Cleaning Solution (PEC-12) Rescue: Use the professional film cleaner PEC-12 (an anhydrous, fast-evaporating solvent) applied to a special lint-free soft cleaning cloth (PEC-PAD) and gently wipe from the inside out in a single direction. This solvent can kill fungi and dissolve oils in 0.5 seconds, without soaking or softening the gelatin layer, restoring decades-old negatives to almost new condition.