Acid-Free Box

Overview

Ordinary cardboard is made from wood pulp, and wood pulp contains lignin. Lignin breaks down over decades into organic acids, and those acids attack photographic emulsions from the outside in. A box of negatives stored in an ordinary shoebox will show edge staining and fading long before one stored in archival board.

Acid-free board is made from purified pulp with the lignin removed and a buffering agent added, usually calcium carbonate, to absorb any acid that does form. It should also pass the Photographic Activity Test, which measures whether a material reacts with photographic images.

The box is only part of the system. The environment does the rest: cool, dry, stable, dark. A perfect box in a damp attic will still lose the negatives.

What it does well

• Prevents the acid migration that ruins negatives in ordinary boxes
• Buffering agent neutralises any acid that does form
• Drop-front boxes make it easy to remove a sleeve without dragging it
• Available in sizes matched to standard sleeve formats
• Turns a pile of negatives into an archive

Safety notes

Working notes

• Store vertically, not stacked. Pressure on a horizontal stack causes scratches and print-through.
• Label the outside of the box, never the negatives inside it.
• Keep the environment stable. Fluctuating humidity does more damage than a steady warm temperature.
• Check the archive every couple of years for staining or vinegar smell, which signals acetate decay.

Compatible with