Creating and managing the ideal environment for archive storage
Jon FleetBusiness Development Manager
Archives include paper and parchment, photographs, negatives and transparencies, and audio-visual materials such as digital records, video and sound recordings. Humidity, temperature, light and air-borne pollutants all contribute to the deterioration of archival materials. These factors must be controlled and monitored to ensure optimum conditions.
PD5454:2012 Guide for the storage and exhibition of archival materials gives recommendations for the storage and exhibition of documents, including books and other library materials and states that “An unsuitable storage environment is one of the commonest causes of damage to archives” and that ”different types of archival material can require quite different storage environments”
As a guide, ideal conditions for most archival materials include an air temperature between 16 – 20°C and a relative humidity between 40 to 55%. Recent standards allow for some change between the minimum and maximum of these settings, such as seasonal changes, providing this change occurs slowly. Sudden fluctuations in humidity with the rapid loss or absorption of moisture can cause microscopic structural damage which will contribute to the overall deterioration of the material and high temperature can also affect deterioration as the speed of chemical reactions increase in warmer conditions.
Air quality is also an important factor when storing documents and free air circulation should be carried out in the storage facility, eliminating the formation of stagnant zones. Adequate ventilation is essential to prevent the build-up of harmful compounds, such as dust, nitrogen oxide, ozone, formaldehyde, sulphur dioxide, volatile organic compounds and carbon monoxide.
What is the best environment for preserving photographic materials?
Photographic materials including acetate and colour negatives, slides, and other associated materials are all vulnerable to fading and deterioration very quickly if they are not stored in the correct conditions. High temperatures and moist air increase deterioration and promote the growth of mould and mildew, which can damage the surfaces and break down the binder layers.
When handling these materials use clean lint-free gloves to avoid damaging them with natural skin oils, keep them in acid-free folders to protect them from dust and light, and store them in a cool, dry, well-ventilated storage area.
What is the best way to store paper documents?
The greatest problem with the long-term storage of paper and parchments is caused by the acidity that may have been introduced during manufacture. Paper produced after 1830 is likely to have a high acidity due to new processes and wood pulp used after the decline of the use of linen and cotton as the main raw materials. Unless this pulp had been chemically treated to remove this acidity a gradual breakdown of the chemical bonds in the cellulose fibre of the paper occurs. This process is greatly accelerated by detrimental environmental conditions including ultraviolet light, and high temperature. Mould is also a problem and may occur if the relative humidity is above 65% for more than 48 hours.
The best storage methods for documents include the removal of any metal paperclips, fasteners, pins and staples as these may cause rust marks, rubber bands as these perish and stain, and horizontal storage in acid-free folders at a steady temperature of 20°C and a relative humidity of 55% with continuous air ventilation. Storage of small to medium size books may also include vertical storage and protection to the spines to prevent deterioration from exposure to dust and light.
How best to care for, handle, and store audio-visual materials
Historic audio-visual materials include phonographic cylinders, reel-to-reel or cassette magnetic tapes, and grooved or optical discs. Deterioration of the quality of sound and image will have occurred from the moment these were produced and even playback can cause degradation of the recordings. It is usual therefore to preserve these recordings as soon as possible in a digital format before storage to ensure that the existing quality is maintained as a digital record. In addition to deterioration over time or during playback careless handling, thermal shock, exposure to light and strong magnetic fields will all affect the quality of the recordings.
For long-term archive storage these materials will benefit from storage in acid-free paper protective sleeves avoiding storage containers retaining static charge and at temperatures of between 8–10 °C and relative humidity of 30–40%.
Is monitoring equipment a good idea for identifying potential storage issues?
Environmental monitoring systems, including temperature, humidity and air quality are excellent means of establishing whether or not the storage area meets any agreed optimum conditions and enables quick identification of any issues. Where storage sites are remote and/or the responsible persons are managing multiple stores an internet connection will give instant access to day to day changes which combined with data logging will enable daily or seasonal fluctuations to be identified and predictive analysis decisions made. When monitoring of climate control equipment is included, the ability to diagnose critical infrastructure faults, and repair and maintain in a timely manner is greatly increased.