Physical hazards

Environmental and physical hazards

All items made from organic materials will inevitably suffer some deterioration over time, because of the inherent nature of the materials and the chemical processes used in their construction.

Parchment and good quality rag paper are very stable if stored correctly. But most paper from the mid-nineteenth century onwards is made of wood pulp. It contains acidic chemicals which naturally tend to degrade the paper. Acidity is the big enemy of modern paper, particularly mass-produced commercial paper. It is particularly important to store important modern papers carefully, wrapping them in acid-free packaging, to stop the acidity bleeding through and affecting neighbouring materials.

Deterioration occurs at a much slower rate if the material is stored in the correct environmental conditions.

It is impossible to separate these factors completely, as all three are present within the environment. It is the combination of changing levels of humidity, temperature and light levels that can accelerate damage to documents.

Running water

Flood water is an obvious danger. Immersing a document in water will cause it to go pulpy. Water-based inks will run and spread, making it impossible to read the document.

Humidity

Water in the atmosphere (damp, or high humidity) will also cause damage, especially at higher temperatures. It can encourage mould to grow. Mould causes spots to develop on the document, which will discolour it and make it very fragile.

Variations in temperature and humidity cause stress to the documents. A quick increase in warmth and humidity can stimulate the growth of mould spores. Dry conditions can make paper brittle.

Damp conditions can cause parchment to ‘cockle’, or change shape. In extreme cases, parchment membranes exposed to too much heat and water can stick together and be virtually impossible to prise apart.

Fire

Fire is another very obvious danger. Even if no flames touch the archive materials, high temperatures will lower the humidity and cause brittleness. Smoke also causes damage.

Light levels

Light tends to fade inks on paper or parchment. The danger caused by exposure to light explains why exhibition spaces are often dimly lit, and why photocopying is often restricted.

You may have noticed that newspapers very quickly become brittle and discoloured if exposed to light. All wood-pulp paper will be affected by light, because of the chemical combination caused by light interacting with chemicals used in the paper-manufacturing process. Newspapers show up this process quickly because they are generally made from low quality paper.

Acidity

Acid chemicals, combined with moisture from the environment, cause marks and stains to develop over time. Brown dots and stains on paper are sometimes called ‘foxing’. Acidity is intrinsic to paper and its extent varies according to the paper’s quality. Seen below are two letters filed consecutively in the papers of the 1st Earl of Portland. The first was written in 1701 on good quality paper, still quite clear and white. The second was written in 1697 on flimsier paper which is now quite discoloured and marked.

Chemical degradation

Leather-bound volumes are vulnerable to a chemical degradation process called ‘binding rot’, which causes the binding to crumble and decay to a fine red powder. The rot is inherent to the tanning process used to produce the leather, but the decay is greatly accelerated when the volumes are exposed to light. The photograph below shows a volume suffering from binding rot, which has been placed in a book box made to fit its dimensions, to keep it protected against further damage. Staining is visible on the interior of the box, where it has come into contact with the affected material.

Box containing bound volume suffering from binding rot (BT 1/1/1/14)

Infestation and dirt

Other external dangers come from failing to secure the storage place against these hazards. Rodents like eating paper and parchment or chewing it up for their nests! Insects and other creepy-crawlies can also cause a lot of damage. Dust harbours mould spores and, if allowed to build up, causes damage.