Introducing preservation for paper-based heritage library and archive collections.

15 June 2012

By Mary Minicka

Historical library and archives collections contain large numbers of documents composed of a wide range of organic materials: paper, cloth, thread, adhesives and a variety of animal skins.  These materials undergo a continual and inevitable natural ageing process that can be retarded, but never completely halted, by taking a variety of measures to ensure the preservation of their collections. What needs to be appreciated is that the damage that occurs to paper-based collections is irreversible and cumulative.

imageImage of damaged pages from a manuscript in Timbuktu showing the effects of the gradual loss of paper. Photo credit: Alexio Motsi and Mary Minicka for the Timbuktu Manuscripts Project.

What is preservation?

Preservation, collectively, refers to all of the measures that are taken to retard or prevent deterioration of-, or damage to documents.  Preservation aims to extend the useful life of heritage collection materials, so that they can continue to be consulted. 

Preservation measures aim to do the greatest amount of good for the greatest amount of documents held in any given collection. The measures look at remedying or, at the very least, mitigating causes of harm and deterioration to documents.  In contrast, interventive conservation treatment repair work tends to focus on a relatively few items and is considerably more expensive as specialist conservators, conservation materials and equipment are required.  Preventative preservation measures can be undertaken by any institution that holds a collection of documents in its care. 

In caring for collections, preservation takes a holistic view:  it looks at the entire environment that any given document is used and stored in.  Specific preservation measures look at:

  • Environmental conditions, including: temperature, relative humidity, light, pollution, dust and dirt.
  • Pests and other biological threats to document collections.
  • Handling and storage of documents.
  • Disaster preparedness and salvage.
  • Issues of theft, vandalism and the security of documents are also important consideration.

Preservation programs need to take into account that many preservation issues are interrelated; for example, good housekeeping in storage areas is a way of both keeping documents clean and dust free, as well as a means of preventing pests gaining a foothold in storage areas.

Environmental conditions

A number of environmental factors contribute to the deterioration of library and archive documents.  Of the most important to consider are: temperature, relative humidity and light.

Light causes the fading of dyes, inks pigments and contributes to the premature ageing of paper cloth and leather.  All kinds of light will affect paper, inks and pigments – however, ultraviolet (UV) radiation is particularly damaging. Measures recommended include using curtains and screening films on windows, using UV filters on artificial lighting and ensuring that lights are switched off in areas that are not in use. 

Relative humidity (RH) is the percentage of water vapour actually held in a specific amount of air, compared to how much that same amount of air can hold at the same temperature and pressure. RH and temperature work together, RH is dependent upon temperature; the higher the temperature, the more water vapour the air can hold and the less it can hold when temperature is lowered.  The control of RH and temperature need to be considered together, as high levels of either temperature or humidity pose a significant threat to collections.  Heat accelerates deterioration; controlled experiments indicate that the chemical processes associated with deterioration are doubled with each 10 °C increase in temperature.  The combination of high temperature and high relative humidity is conducive to mould growth and provides a pleasant environment for insects.  Too little humidity in the environment, however, can lead to desiccation of documents.  The generally agreed upon range for acceptable humidity is between 30 – 65 %; the ideal temperature range is between 19 – 23 °C.

One final point about temperature and humidity is that fluctuations in temperature and humidity are also damaging.  It may be better for documents to be stored at slightly higher levels of temperature and humidity, as long as steep fluctuations are avoided. This is because library and archive materials are hygroscopic.  Hygroscopic materials easily absorb and release moisture in response to daily and seasonal changes in temperature and humidity by contracting and expanding to either absorb or release moisture.  The movement of the materials accelerates deterioration and leads to visible changes such as: cockling paper, flaking of ink, warped covers and cracked photographic emulsions. 

Pollutants, particularly particulate matter (such as dust, dirt, soot and mould spores) can also affect library and archive materials. Gaseous pollutants such as the gasses released by certain types of wood or paint can also affect library and archive materials. 

Pests, other biological threats to document collections, Good Housekeeping Programs (GHP) and Integrated Pest Management (IPM)

Insects, rodents, mould, even stray animals such as birds and cats can cause considerable harm to collections.  Some insects feed on the types of materials found in libraries and archives; while other pests will cause damage simply through the effects of their life cycle on collections, for example, in shredding paper to make nests. 

Increasingly, libraries and archives have realised that relying solely on toxic poisons and fumigants is increasingly undesirable and ineffective.  Increasingly, the approach taken to manage pest activity is to use an Integrated Pest Management (IPM) approach.  IPM programs are designed to prevent pests getting into storage areas and establishing themselves there.  IPM strategies include monitoring for the presence of pests, as well as taking measures to ensure that the book and storage environment is as unwelcoming to insects and pests as possible.  Another IPM-related strategy is a sound building maintenance program, as a sound building fabric is the first line of defence against pests and other threats to heritage collections.

Insects and pests prefer quiet, dark, moist environments that also have food sources close at hand.  Good Housekeeping Programs (GHP) are used to prevent these conditions from arising by keeping storage areas clean, tidy, and to eliminate potential sources of food and comfort for insects and pests.  Good Housekeeping is a systematic program to keep storage areas as clean and sterile as possible and forms an important, low toxicity approach to helping to keep eliminate pests from the storage environment.

Handling and storage

How books and documents are stored and used contributes much to their ability to survive.  Thus, encouraging ideal handling techniques, for both staff and researchers, is an essential part of any institution’s preservation strategy.   

Good storage practises go a long way to ensuring the preservation of collections by minimising risks of pest infestation, mould growth and damage from leaking water to the collection.  A good storage environment needs to be clean and clutter free.  Documents should not be stored on the floor, or on top of shelving units. Collection items should also be cleaned regularly, as part of a regular good housekeeping program.  Dust can be abrasive and often contains pollutants that can foster mould growth and pest infestation. 

Shelving should ideally be made from inert materials and appropriate to the size of the books and documents stored on the shelves. Protective enclosures for fragile and damaged books and documents will also help to preserve books and documents from further damage or loss of lose parts.

Disaster preparedness

Library and archive collections face a considerable threat from disasters such as flooding, fire and other unforeseen events that have the potential to inflict catastrophic loss or damage to heritage collections. Planning for a disaster will not prevent emergencies happening; it will ensure that the response to a disaster is faster and better coordinated, making the ultimate impact of a disaster much less catastrophic than it could otherwise be.

There are three aspects to disaster preparedness: the disaster plan that will provide a detailed guide for the initial response to an emergency, as well as to the salvage and rescue of the collection; a minimum amount of supplies to use for responding to the disaster; and a disaster response team that will oversee and guide the initial response to the disaster and ensure a return to normalcy following the disaster. 

Online resources for more detailed information about preservation

Canadian Conservation Institute. Notes on preservation (“Conserve-o-grams”).

Collections Link. Collections care.

Conservation Online

International Federation of Library Associations (IFLA).  Principles for the care and handling of library material.
http: //archive.

Northeast Document Conservation Centre. Preservation leaflets.

British Library. Preservation Advisory Centre, Caring for collections (e-induction)

reCollections – Collections Australia Network (CAN).  Caring for collections.

Please bear in mind that many of these resources are European or American, while the basic principles of preservation are universally applicable, archives and libraries in other parts of the world face further challenges.  The following source may be a useful guide to working with some of these challenges:

International Council on Archives.  Preservation of archives in tropical climates: an annotated bibliography.

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