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What is acid-free plastic?

Published in Archival Materials 1 min read

"Acid-free" doesn't accurately describe archival-quality plastic. Instead, the ideal characteristics for plastic used in preservation are that it be inert and stable.

In more detail:

While the term "acid-free" is often associated with paper products designed for archival purposes, it's not directly applicable to plastic. This is because the concern with paper is often the presence of acids (and lignin) that can degrade the paper over time. Plastic, however, degrades through different mechanisms. The qualities you should seek in archival-quality plastic are:

  • Inertness: The plastic should not react chemically with the items it's storing or with the environment. This prevents the plastic from causing damage, discoloration, or deterioration of the stored objects.
  • Stability: The plastic should resist breaking down or releasing harmful substances over extended periods. This ensures long-term protection of the enclosed items.

Plastics to avoid for archival storage:

  • Polyvinyl chloride (PVC or Vinyl): PVC is known to release acids as it degrades, which can be very damaging to artifacts. Therefore, it is not suitable for archival storage.

Essentially, when choosing plastic for preservation, focus on plastics specifically manufactured for archival use and clearly labeled as inert and stable.