What “archival” paper means, and what it does not

A term without a single definition

“Archival”, “museum grade” and similar labels are not protected terms. Manufacturers use them for papers with properties associated with a long life: no acid, no lignin, an alkaline reserve and pure fibre.

The international standard ISO 18916, which describes the Photographic Activity Test (PAT), points out that passing the test does not on its own mean a material is archival. The previous edition of the standard, from 2007, states explicitly that the term “archival” has no clear definition and that the standard therefore does not use it.

When reading a box, look for specific properties rather than adjectives.

What to look for

Statement on the box or data sheet	What it means
acid-free	the paper is not acidic; acidity speeds up the breakdown of cellulose
lignin-free	lignin from wood yellows over time and makes paper acidic
buffered (e.g. with calcium carbonate)	an alkaline reserve that neutralises acids from the surroundings
ISO 9706	the permanence standard for document paper; Fine Art paper manufacturers often cite it
OBA content	the amount of optical brighteners (see below)

ISO 9706 assesses the paper, not the image on it. It says only indirectly how long the colours of a print will last.

Optical brightening agents (OBAs)

Optical brightening agents are substances that absorb ultraviolet light and re-emit it as visible blue light. They make paper look whiter and “cleaner”. They have two drawbacks:

• their effect wears off over time, so compared with its original state the paper looks warmer, even yellowish, although the fibre itself has not changed,
• the paper looks different under light with different amounts of UV: behind UV-filtering glass or under LED lighting it looks less brilliant than in the shop.

Manufacturers state OBA content in their data sheets. Hahnemühle, for example, gives “none” for Photo Rag® Baryta, “very low” for Photo Rag® 308 and “moderate” for FineArt Baryta. Paper without OBAs is not automatically better. It is, however, more predictable.

Enclosures, mounts and albums: ISO 18902 and the PAT

Materials that touch a photograph are covered by ISO 18902. It sets physical and chemical requirements for albums, enclosures and framing and glazing materials, including materials for inkjet prints. Part of it is passing the PAT under ISO 18916, which tests whether a material reacts with the photograph.

The Library of Congress recommends that enclosures for storing photographs meet the requirements of ISO 18902, including the PAT. If a supplier states this, it tells you more than the word “archival”.

What the life of a print depends on

1. Ink: pigment inks are generally more light-fast than dye inks.
2. Medium and coating: it is the combination of ink and a specific paper that counts, which is why manufacturers test permanence for particular pairings.
3. Light: especially intense and prolonged exposure. UV filters help, but visible light fades colours too.
4. Humidity and temperature: high humidity and heat speed up chemical reactions.
5. Air: ozone and pollutants damage dye-based prints in particular.
6. Enclosures and mounting: acidic board, sticky tape and PVC sleeves harm even the best paper.

In practice

• For prints that need to last, choose an acid-free, lignin-free fibre-based medium and pigment inks.
• If a stable paper tone matters to you, prefer paper with no or low OBA content.
• When framing, use a museum-grade mount and UV-filtering glazing. See Mounts and Frames and glazing.
• Keep originals in the dark in PAT-tested enclosures; hang copies on the wall. The method is in Storing photographs.