Archives are inherently fragile because of the materials they are made of (including acidic paper and the chemicals in inks), their treatment and storage before being earmarked for preservation, and their susceptibility to damage. In order to preserve them in the long-term, they need to be stored in conditions which are cool, dry and stable, with minimum exposure to natural or artificial light. They also need to be packaged adequately and handled carefully. Providing good storage conditions slows down deterioration over time and helps to prevent damage from dirt, mould or pests.
Increasingly, we are being asked to look after archives which exist only in digital formats, which pose their own problems in relation to long-term preservation.
In an ideal world, all archives would be stored in perfect conditions, complying with international standards – secure, in a stable suitable environment, and protected from risks. In the real world many collections are stored in far from ideal conditions such as in attics, basements, garages and metal industrial units, subject to extremes of temperature and humidity, and at risk from fire, water, pests or theft. Risk cannot be avoided completely, but steps can be taken to manage and minimise such hazards. This document aims to offer some practical and realistic advice to help you to preserve your collections for the future.
The key current standards for archival buildings and storage are:
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 [ISBN: 978 0 580 90371 7].
BS 4971:2017, Conservation and care of archive and library collections [ISBN: 978 0 580 94654 7].
You may still come across references to BS 5454:2000 or PD 5454:2012, the first version of which was issued in 1977, and which remained the key standard in the sector until replaced by the two current documents.
Although these standards lay down best practice, they are realistic in that they recognise the limitations of many existing premises. If you are having a new storage area built or converted, please make your architects aware of these standards at an early stage. As is the nature of such documents, they are very technical, but they still contain a lot of useful advice about environmental conditions, shelving, packaging and hazards that can be used by all custodians of archives, as well as the specialist advice on construction. There are many practical steps you can take to protect your collections by identifying and mitigating risks.
Organisations with limited resources may not be able to purchase copies of the Standards, but your Sector Development Manager will be able to offer advice on their contents and make suggestions on how to comply with specific aspects of them.
Unless you are fortunate to have a new-build planned and financed, you will most likely have to make the best of whatever storage area you are assigned.
Services running through the storage area should be minimal. Avoid areas with gas, water or sewage pipes, particularly main risers, or where there are hazards from above such as kitchen areas and toilets. Electrical wiring, sockets, lighting and equipment should be checked for safety to reduce the fire risk, and where possible, any wiring should run through metal conduits. Master switches for electrical circuits should be outside the storage area.
The roof and any windows should be checked to make sure they are watertight, and any nearby gutters, downpipes and drains should also be regularly checked for blockages, and well maintained. If the area is known to be liable to flooding, lower shelves should not be used for storage, and plans should be in place to quickly evacuate the contents most at risk.
Be aware of open roof spaces above the storage area, through which fire can easily spread. Also think about potential hazards in adjacent areas, such as combustible chemicals, fuel, and wood. Storage areas should not be adjacent to any areas (internal or external) where hot work such as welding is carried out, because of the fire risk. Ideally, the storage area should have fire-resistant walls, ceilings, floors and windows, and four-hour resistant fire doors. Smoke detectors should be fitted inside and outside storage areas, and connected to the site’s alarm system.
The floor-loading should be sufficient to bear the weight of the collections and shelving. For this reason archives can often be stored in basements, which can have particular risks of flooding or dampness.
Solid floors are preferable to carpets in storage areas, as carpets can harbour dirt and insects.
For a small collection it may not be feasible or appropriate to have a separate storage room, but consider investing in a secure, fire-proof cupboard. Even a normal metal cupboard can be locked and will offer some protection.
Archives can be endangered by extremes or rapid fluctuations of temperature and humidity. A relative humidity of over 60%, particularly for a prolonged period of time, poses the risk of a mould outbreak which can be damaging to both documents and people, and is expensive to remedy. On the other hand, hot and dry conditions can make materials brittle.
Different materials require different environmental conditions for their long-term preservation. In general, films and photographs should be stored in very cold conditions. Paper can be stored in cool conditions. In practice, collections are likely to be mixed, and also contain other media and materials, such as paintings, trophies and uniforms. In all but the largest collections, a compromise will have to be found, assuming that the custodians have any control over the environment at all. If parts of the storage area are noticeably cooler than others, take advantage of this and locate some of your collections accordingly.
The current guidelines for Temperature and Relative Humidity for mixed-media collections are an annual average of less than 18oC (with a maximum of 23oC and minimum of 13oC), and a maximum of 60%RH, and minimum of 35%RH. Any fluctuations should be steady and gradual. BS 4971:2017 goes into much greater detail, and makes additional recommendations relating to photographic, audio-visual, and machine readable material. A useful summary of the advice for the care of such modern media has been produced by the Religious Archives Group, see https://religiousarchivesgroup.files.wordpress.com/2020/02/section-3-modern-media.pdf
In most archives that have environmental controls it is heavily reliant on plant, which is expensive to install, operate and maintain. The current trend for new buildings is for passive environmental control to be built in – this includes the use of thick/insulated walls, sometimes below ground level, to minimise changes in temperature and humidity, and minimise the need for mechanical environmental controls. In existing buildings, extremes can be mitigated by increasing air-tightness, and using de-humidifiers and background heating.
You should invest in monitors so that you can be aware of how your storage area performs over the course of the year, and can take appropriate steps to minimise fluctuations. Thermo-hygrographs record the levels of temperature and Relative Humidity on a chart, to show fluctuations over time. Relatively inexpensive electronic thermo-hygrometers, which can be hand held or wall mounted, display the current temperature and Relative Humidity. You can also purchase small electronic monitors which sit on shelves or in boxes or display cases. For these, you download the information periodically, so they show fluctuations over time rather than giving instant readings. It is important that monitoring equipment is correctly calibrated, and periodically recalibrated, if it is to give accurate results.
Dirt, dust and pollutants are an issue, particularly in urban areas, and are hard to control unless your storage area is relatively air-tight, and filtered air-handling equipment is installed.
Ultra-violet light can be harmful to archival materials so, as a minimum, blinds should be installed on any windows.
The area in which archives are stored should be secure. Ideally, there should be no external doors or windows and the roof should be secure. Any ground-level windows should be at least locked, and preferably blocked up or barred. Internal doors should be locked when not in use, and access to the keys restricted to staff responsible for the archives and caretaking staff. If small collections area kept in cabinets rather than a specific store room, these should be kept locked when not in use. Intruder and fire/smoke detectors and alarms should be installed if possible.
Only authorised staff or volunteers with responsibility for the archives should normally have access to the storage areas, and only they should remove any items from storage. A paper slip should be left in place of any document removed, so that it is clear what has been removed, who currently has it, and where it should be eventually be replaced. A log should be kept of all withdrawals and returns.
External contractors and maintenance staff should be supervised at all times when carrying out work in storage areas in case of accidents or theft. Many fires in historic buildings start as a result of hot-work (welding, soldering etc) being carried out by contractors, and they may not appreciate the valid reasons for not having open liquid containers in archive storage areas.
Wherever possible, archival items should be packaged. Boxes help to protect items from disorder, dirt and water, and can help to minimise environmental fluctuations. The best boxes are made from acid-free card, with brass staples. If your budget does not stretch to the purchase of specialist boxes at present, you can use any strong, clean cardboard box as a temporary solution (e.g. photocopy paper boxes), but do not use boxes that have metal fastenings or been used for storing food as these may attract pests. Plastic boxes are not normally recommended because many contain chemicals that could affect the contents, and if they have airtight lids there is a risk of condensation leading to mould.
Folders and boxes should be of an appropriate size so that items can be stored flat without being crushed or folded. If possible the contents of a box should be packaged in clearly labelled folders made from acid-free paper or card, which can be tied up with unbleached linen tape if necessary. This can help to keep the contents in order and prevent them being damaged while looking through the box for a specific item. Small items within a larger box should be placed within a suitably sized folder to help protect them. Unrelated items within a box should be packaged separately so that they don’t get mixed up and can be easily identified. If loose items were originally in a file or bundle it is useful to number them consecutively so that the original order can be maintained. It may help to break down the contents of such files and bundles into smaller units (say 50-100 pages) which are easier to package.
Fragile volumes are best protected by custom-made book boxes if you have sufficient resources.
Larger items that won’t fit in boxes can be wrapped in suitable packaging such as acid-free card, calico, or Tyvek (a breathable polyethylene material). Again, unbleached linen can be used to tie up such packaging. Normal card luggage tags can be used as labels, though conservation-grade alternatives are also available.
Map cabinets can be used for storing large flat items. If you use wooden map cabinets, lining the drawers with archival paper or card can help to protect against any acid in the wood.
Photographs should ideally be stored in archival polyester, polyethylene or polypropylene pockets or sleeves. Brand names include Melinex, Mylar and Polymex. Theses should then be stored within archival boxes if possible.
Boxes should not be over-filled as this can cause the contents to be crushed and damaged, and can also make the boxes heavy and hard to handle, increasing the risk of them being dropped and posing a Health and Safety issue for staff and volunteers.
Shelving can be metal or wooden, static or mobile, depending on budget. The important thing is that it is strong enough to bear the weight of the collections; suitably spaced so that top shelves can be safely accessed; and there should be a clearance of at least 150mm (6”) at floor level in case of flood. Ideally, shelving should not be placed directly against an exterior wall or window, and should be open to allow for a free circulation of air. Wooden shelving is more of a fire risk unless treated with retardant, and when new can also give off acetic acid, so metal racking tends to be preferred.
The higher the shelving you install, the more you will need to use steps in order to safely access material. Bear this in mind when planning the aisles between shelves. Ideally, steps should have handrails for safety, and wheels to enable easy movement.
For staff Health and Safety, particularly heavy items should be stored at lower levels, and their weight clearly marked on the packaging. It is also worth investing in wheeled trollies so that heavy items can be wheeled around rather than carried.
Very large items may require different forms of storage such as long wall-mounted shelves or map cabinets.
Storage areas should be kept clean and tidy. Vacuuming will normally be sufficient, and it may be worth investing in a specialist museum vacuum. Do not use water, or cleaning materials such as sprays and polishes which can contain chemicals that could harm the collections. If an area is particularly dusty, consider wearing face masks during cleaning.
The cleaner, tidier and better lit the storage area, the easier it is to spot problems such as mould or insect/rodent damage. Staff and volunteers should be trained to know what to look out for. Invest in some insect traps so that you can monitor the level of any problem.
Boxes, folders, rolls and shelves should be clearly labelled so that items can be easily found. A shelf-list can be a useful tool for locating items. However, think about the security of particularly valuable items, and consider acquiring a safe if this might be an issue.
The major risks to your collections are fire, flood, theft and unauthorised access. What would you do if disaster struck? It would certainly be a stressful, confusing, and potentially hazardous situation, made even worse if you had no idea what to do, or who to contact. For this reason, it is wise to prepare a comprehensive and up-to-date Disaster Plan for your site, and for it to be easily accessible by key personnel.
First think of the things that can potentially go wrong on your site, then look at what steps you can take to prevent things going wrong, and then plan what to do if despite your efforts there is an incident of some sort.
Issues to consider include the following. What is the fire resistance of your walls, ceilings and doors? Are fire extinguishers available and have staff been trained in their use? Is there drainage with one-way valves, to let water out of the storage area in the event of flood or fire suppression? Where will you temporarily store salvaged collections? Where will you dry slightly damp material? What will you do about badly damaged material? If your collection contains significant material, consider subscribing to a disaster recovery company with bulk freezing and drying facilities.
Your Disaster Plan should include key contacts (home numbers for staff, as well as contact details for utilities and contractors), together with responsibilities and procedures. If you are an Accredited Museum, or moving towards Accreditation, this should already be in place. Key staff should have copies at home so that important phone calls can be made even if it is not possible to get on-site immediately.
Consider going on courses to learn about salvage techniques. Find out if there is disaster group for museums in your region that you can join. You may wish to store a basic disaster kit containing items such as wellingtons, gloves, torches, mops and buckets, plastic sheeting and blotting paper on your premises to help you deal with small-scale issues, such as a minor leak. But be realistic – in the case of a major incident the emergency services will not let you into the building until it is safe.
There are commercial organisations offering salvage and restoration services including bulk freezing and storage of soaked books and documents, so that they can be thawed and treated systematically. If your own resources are sufficient, you might consider subscribing, or joining a local consortium, in case of a flood, or damage caused by fire suppression. Such organisations may also offer training and advice on disaster planning.
Archives are difficult to insure because they are generally irreplaceable. Available insurance tends to cover treatment costs in the event of a damage, and this is another thing to consider for peace of mind if your organisation’s resources allow, and your collections are of particular historical or technical significance.
See https://www.nationalarchives.gov.uk/documents/information-management/memo6.pdf for some introductory advice on risk management and recovery plans. The London Fire Brigade has issued some detailed advice, including template documents for preparing emergency response and salvage plans for heritage buildings at https://www.london-fire.gov.uk/safety/property-management/fire-safety-in-heritage-and-historical-buildings/emergency-response-and-salvage-plans-for-heritage-buildings/
Most sites are only left unattended for a few days at a time, such as on weekdays or weekends (depending on opening patterns), and over the Christmas or Easter holidays. Some organisations check premises periodically over such closure periods to make sure they are secure, alarms are working and there are no other issues. The coronavirus pandemic of 2020 raised the issue of unplanned extended closures and how best to lock-down an archive repository through measures such as unplugging non-essential equipment, turning down the heating, making arrangements for remote working, and maintaining contact with stakeholders.
In the museum sector it is common to keep a copy of the Accessions Register on a separate site so that the information is retrievable in case anything happens to the original. The location for the copy needs to be secure because of the personal data contained in the Register, so another repository would be preferable to a private home. If your catalogues are not computerised, you might consider lodging copies of the most important catalogues off-site as well. Such copies could be invaluable if an incident affects your working areas rather than your storage areas.
Digital archives, whether born-digital, or created as part of a deliberate digitisation programme, pose their own problems in terms of long-term preservation. Even the smallest organisation will now have digital files – word-processed minutes, spreadsheets of accounts, emails, and digital photographs. The specific problems posed by digital archives are still being addressed by the archives sector, confidence and training levels are generally low, and there are few dedicated digital archivists. However, organisations such as the Digital Preservation Coalition, The National Archives and JISC are developing accessible advice and training.
Two key issues to consider are back-ups and migration.
The back-up of electronic files is essential in case of equipment failure, accidental deletion, or data-corruption. This includes administrative files of your organisation, working papers, catalogues and digital archives in your collections. For organisations with limited resources, back-ups could take the form of CDs/DVDs or portable hard drives. For larger organisations, remote servers, data tapes, and/or cloud storage may be used. Ideally, there should be several copies of all data, at least some of which should be stored off-site.
Migration is necessary in order to keep digital files usable. Software is constantly evolving, and specialist programs, or even older versions of commonly used programs may become obsolete. You don’t want to be in the position of having your data stored on old floppy discs which can’t be read because your computer lacks disc drives, or having data safely stored on your system that is unusable because of obsolete file types, or the lack of relevant software. Migration, every few years, enables data to be stored in up-to-date versions of programs of, if necessary, transferred to a different program which still enables it to be accessed. Technology such as Checksums is being developed to help monitor any corruption of data over time.
A range of specialist Digital Asset Management Systems are available to assist with the long-term preservation of digital archives. They require a reasonable level of technical competence to set up and use, and there can be significant costs. Some systems are proprietary while others are open source. See https://www.nationalarchives.gov.uk/documents/archives/cms-dams-options-for-archives.xls for a comparison of the features of different systems.
The NDSA Levels of Digital Preservation are one method of self-assessing your organisation’s state of preparedness for the challenges of digital preservation. See https://ndsa.org/activities/levels-of-digital-preservation/ for their Level of Digital Preservation grid and downloadable explanations.
As with physical archives, an awareness of the issues that might affect your collections, and small steps towards addressing these, can all help.
This guidance links to Sections 1.4 (Resources: Spaces and storage) and 2.4 (Collections Care and Conservation) of the Archive Service Accreditation Standard.