Preserving physical photographs requires a precise understanding of material science to prevent chemical degradation, yellowing, and mechanical damage over decades of storage.
The Chemistry of Photo Degradation
To safely mount and store photographs, you must first understand the chemical enemies of photographic emulsions. Traditional silver halide prints and modern pigment-ink prints rely on delicate surface layers that react easily with environmental contaminants. The primary culprits of photo degradation are acidity, lignin, and volatile plasticisers. Standard commercial paper contains lignin, a natural organic polymer that binds wood fibres. Over time, lignin oxidizes, releasing acidic compounds that break down the cellulose in album pages and migrate into the photographic paper, causing characteristic yellowing and brittleness. Furthermore, many cheap adhesives and plastics contain polyvinyl chloride (PVC). PVC releases harmful hydrochloric acid gas as it degrades, while its added chemical plasticisers migrate as oily residues, liquefying photographic emulsions and causing permanent sticking.
Selecting Chemically Inert Mounting Materials
Safe preservation depends entirely on using materials that are chemically inert, meaning they will not react with the photographic paper or emulsion. When selecting an album, ensure the pages are certified acid-free and lignin-free, preferably meeting ISO standards for photographic storage. For securing the photographs, three primary methods exist, each with specific chemical profiles. First, mounting corners made of archival polyester or polypropylene are the safest physical option because they require no adhesive contact with the photograph itself, allowing the print to expand and contract naturally with temperature changes. Second, if using double-sided adhesive, choose a pressure-sensitive acrylic transfer tape that is acid-free and passes the Photographic Activity Test (PAT). Acrylic adhesives do not dry out, turn yellow, or bleed into the paper fibers like rubber-based glues do. Third, for traditional scrapbooking, highly purified wheat or rice starch paste provides a reversible, neutral-pH option that can be dissolved with a tiny amount of moisture if the photo ever needs to be safely detached.
Step-by-Step Mounting Technique
Proper execution prevents physical stress on the prints and ensures clean alignment without chemical contamination. First, prepare a clean, flat wooden or glass workspace. Wash your hands thoroughly to remove lipids and salts, and put on clean, lint-free white cotton gloves. Skin oils contain sebum, amino acids, and lactic acid, which transfer easily to photographic emulsions, attracting fungal spores and causing irreversible fingerprint staining. Lay down the album page and position the photograph using a clean, non-reactive ruler to align it. If using mounting corners, slip a corner onto each of the four corners of the print while it is face up. Gently place the photograph onto the album page. Once positioned, press down firmly on the adhesive tabs of the corners. This technique prevents the photograph from buckling, as it is not bound directly to the page. If you must use double-sided archival tape, apply short strips of tape to the back of the photograph, leaving at least a one-centimeter margin from the edges. This margin prevents adhesive squeeze-out when the album is closed and compressed.
Optimal Environmental Storage
Once your album is assembled, physical storage conditions dictate the longevity of the preservation work. Store albums horizontally rather than vertically; this distributes weight evenly and prevents gravity from bowing the heavy pages or causing adhesive-mounted photos to slide down over time. Keep the storage environment stable, aiming for a temperature below 20 degrees Celsius and a relative humidity between 30% and 50%. High temperatures accelerate chemical reactions, including the hydrolytic degradation of paper, while high humidity encourages mold growth and gelatin swelling. Avoid storing albums in attics, basements, or near heating vents, where fluctuations in moisture and temperature are extreme.
