Environmental Management for Paper Archives
What is the environment?
This refers to:
Relative humidity (RH)
Temperature
Light
Pollutants
Why manage the environment?
RH, temperature, light and pollutants are all agents of deterioration. Left uncontrolled and/or incorrect they cause damage to your archives and increase their rate of deterioration.
Incorrect RH
Relative humidity (RH) is the measure of what most of us refer to as humidity. It can be too dry (low RH) or too damp (high RH).
When warm air is cooled, the RH increases, leading to problems of damp. The opposite happens when cold air is heated, the RH falls.
A high RH (damp) can cause:
Mould.
Increased pest activity.
Mechanical damage such as warping and distortion of boards, cockling of paper and sticking to glass for framed objects.
Corrosion of metals such as book clasps, paper clips and other metal fasteners.
A low RH (dry) can cause:
Embrittlement of objects.
Mechanical damage such as splits, tears and cracks.
Chemical deterioration such as yellowing of paper.
Image shows a book bound in parchment where the cover has buckled and distorted. Incorrect RH: distorted parchment bound volume.’ Image courtesy of Victoria Stevens ACR
Image shows a close up of the edge of a document showing surface mould. Incorrect RH: surface mould. Image courtesy of Victoria Stevens ACR
Image shows three volumes stacked with mould showing on their covers. Incorrect RH: surface mould. Image courtesy of Victoria Stevens ACR
Incorrect temperature
Temperature controls how fast your archives fall apart. The warmer it is, the faster your archive material will deteriorate. Temperatures that are too high can also cause:
Softening of waxes, resins and coatings, leading them to become tacky and easily marked when handled and to absorb dust more easily.
Failure of adhesives.
Increases in the lifecycle of some insect pests.
A temperature which is too low can cause:
Physical damage. Objects can become stiff and brittle, with the result that they are more likely to crack when handled.
Image shows a photograph of a tree where the bottom half of the image is destroyed by pink, purple, grey, mottling. Vinegar syndrome. Image courtesy of West Yorkshire Archive Service
Light
All light is damaging but light with high concentrations of blue and UltraViolet [UV] such as daylight and unfiltered fluorescent light is the most damaging. Light damage is cumulative and cannot be reversed.
Light causes:
Fading.
Yellowing of papers and boards.
Embrittlement of papers and boards.
Heating of the object, and as such becomes a form of incorrect temperature.
Image shows a book being held showing the bright red front cover and the spine faded to light red. ‘Light damage on book’. Image courtesy of National Library of Scotland
Pollutants
Pollutants can be dust, skin, hair, fibres, soot and pollen which cause dirt, abrasion and can attract insect pests and mould. Pollutants can also be gases from aerosols, paints, glues and air fresheners. These gases can cause fading and discolouration and make the paper and card supports brittle. Pollutants can also be intrinsic (from the object itself) such as from iron gall ink, pins and inclusions such as hair and ribbons These intrinsic pollutants can cause acidification, discoloration and staining, and may accelerate the rate of deterioration.
Image shows a row of books with dust on the top of the books. ‘dust on book’. Image courtesy of National Library of Scotland
Good practice for RH and temperature
It is no longer the case that a standard set of parameters for RH and temperature should be applied to all collections regardless. The sector is moving away from a one-size-fits all approach to a context based approach. This means providing environmental conditions which mirror the historic conditions the materials have been kept in over time, the historic annual RH averages, seasonal changes and geographical location which take into account risk.
BS 4971:2017 states ‘Although no single set of environmental conditions is ideal for storing every type of archive material, to slow the rate of decay of all archive material there should be an emphasis on keeping the temperature low and the RH moderate’. It continues ‘The selection of a suitable storage environment for an archive [...] collection should be based on the range of materials it contains and on the long-term sustainability of maintaining those environments’.
Paper based archive materials benefit from storage, display and use in consistently cool conditions. Temperature fluctuation poses a low threat to archive materials. However, temperature fluctuation may cause a correlating fluctuation in RH. A consistent RH in the range of 35% to 60% should be maintained. Gradual change in RH and temperature is acceptable. Microclimates should be used for paper archival material which has specific RH requirements.
Measuring RH and temperature
There are a number of methods available to measure the RH and temperature. These include:
Stand alone monitoring. Also referred to as spot reading, using a hand held device. This allows you to take a quick reading of current conditions
Dataloggers. Also referred to as continuous recording equipment. Automatically record conditions at intervals set by you. They either download the data regularly into a computer or the data is downloaded manually. Dataloggers capture short term changes which may occur over a few minutes and long term changes occurring over several months.
Image to add:
Image shows a row of old books with a small white device with an aerial sitting on the shelf. ‘Loggers: Telemetric lux logger’. Image courtesy of Victoria Stevens ACR
Image shows a shelving unit with a small white device with an aerial (branded Hanwell) and a smaller yellow device (branded Tiny Tag) sitting on the shelf. ‘Loggers: Tiny Tag and Hanwell freestanding loggers’. Image courtesy of Victoria Stevens ACR
Image shows a bookshelf with old books on it with a small blue and yellow device with a grey display screen displaying "60 lux". ‘Loggers: Lux meter’. Image courtesy of Victoria Stevens ACR
Telemetric systems. Also referred to as continuous recording equipment. Automati cally record conditions at intervals set by you. They are radio systems connected to a radio transmitter which sends a signal to a receiver. Telemetric systems capture short term changes which may occur over a few minutes and long term changes occurring over several months.
It is not sufficient to measure, record and archive data for RH and temperature, it must be reviewed and interpreted to understand the environmental conditions that your collections experience. It should be acted upon when necessary.
It is useful to monitor RH and temperature inside boxes and other storage enclosures/furniture. The external conditions may be very different from those occurring inside boxes. Boxes and other enclosures protect archival materials from changes in RH.
Monitoring the environment is an ongoing procedure and it is important that your equipment produces accurate and reliable data. You should maintain your equipment and calibrate it periodically.
Choosing monitoring equipment
What you choose depends on:
Your budget.
Why you are monitoring, i.e. is it short term or long term, how much detail do you need?
How much time you have available to collect, review and interpret data.
Your building. Sometimes there can be problems with transmission in radio telemetry systems through the structure of historic buildings and interference from other radio systems.
Each type of monitoring method has pros and cons. These include:
Stand alone monitoring
√ Easy to use X Can be inaccurate
√ Usually inexpensive X Do not record data
√Can take readings wherever needed X Readings have to be taken manually
Continuous monitoring
√ Easy to use X Can be expensive
√ Take readings all the time X Can be difficult to use
√ Easy to compare data over time X Can break down
Sources and resources
BS 4971: 2017 Conservation and care of archive and library collections
BS EN 16893:2018 Conservation of Cultural Heritage. Specifications for location, construction and modification of buildings or rooms intended for the storage or use of heritage collections
Managing the Library and Archive Environment, Preservation Advisory Centre, British Library, Jane Henderson, 2013
https://www.bl.uk/conservation/guides
Good Practice for Environmental Conditions for Storage and Display in the UK
https://www.icon.org.uk/resource/creating-sustainable-environments.html
Preservation Equipment - for stand alone monitors and dataloggers
https://www.preservationequipment.com
CxD - for stand alone monitors and dataloggers
https://www.cxdinternational.com
Meaco - Radio telemetry
Hanwell - for dataloggers and radio telemetry