Come and see us in person to undertake research on our site. To prepare for your visit and learn about our Covid-secure measures please see here 

May - June half term holidays opening

Gloucestershire Heritage Hub will be open as usual on Tuesday 31st May and Wednesday 1st June, but will be closed on Thursday 2nd and Friday 3rd June in line with the Platinum Jubilee Bank Holidays.

Heritage Hub Collections Care training

Online Collections Care training

How to preserve your community or family archive

Advice on how to protect and look after your physical archive


Collections Care 4: the ten agents of deterioration

Want to know how to prevent damage to your collection? Want to know what to look out for?

First – know your enemy! Then Avoid, Block, Detect, Respond, Treat.

As we know from Coronavirus, our enemies are not always easy to see! But the fantastic people at the Canadian Conservation Institute have done a major piece of work helping us to understand what they might be. They have come up with a list of 10 “agents of deterioration” that threaten heritage objects. Taking time to think systematically about the risks these agents pose allows us to determine how best to minimise damage.

Remember: damage (and loss of historical and/or financial value) will only happen when the item is made from a material that is a) susceptible and b) is exposed to the threat (agent).


The 10 agents of deterioration are:

1) Physical forces: Ranging from a sudden major impact to repeated minor events. Handling items means that there is a chance they can be damaged, soiled, scratched, broken, torn, crumpled, dented. To reduce risk: follow safe handling practice, and provide protective enclosures, such as boxes or folders made of archival quality material.

2) Thieves and vandals: Damage to, and loss of items is not necessarily dramatic or deliberate. Vandalism can be mindless, a lack of appreciation, a moment of boredom. And have you ever lent something and not got it back because the borrower forgot, didn’t understand you wanted it back or unthinkingly passed it on to someone else they thought might interested? To reduce risk: have good supervision, good tracking and security arrangements, and written and signed lending agreements!

3) Fire: A scary one – with the potential for sudden and complete destruction! To reduce risk: ensure you have good preventive measures and regular maintenance of your fire alarms.

4) Water: This could be from flooding, a leaky roof, condensation, fire suppression, burst pipes, spilled drinks and so on! To reduce risk: introduce measures such as regular maintenance, good housekeeping, using protective enclosures, and banning drinks from areas where documents are stored and used.

5) Pests: Any living organism that damages or destroys collections, including a number of different insects, rodents, birds, and even mould. To reduce risk: ensure good housekeeping and good environmental conditions (not too warm and/or damp). You can also set insect traps to see what is about and monitor numbers.

6) Pollutants: These could be chemical compounds (gas, liquid or solid), that cause unwanted reactions in materials. Gases or particulates from outside. Or from inside: dirt and oils from hands, accidental staining with ink, food and drink, and enclosures of poor quality materials such as acidic papers and unstable plastics. To reduce risk: keep your documents/items in a good environment, ensure that food and drink is kept away, and use archival quality materials for protective enclosures.

7) Light: Exposure may occur when items are used and displayed, and even when in storage if unprotected and in direct light. Think fading of book spines on open shelves, or yellowing and embrittlement of newspaper. Light and UV radiation provide energy to fuel chemical reactions that cause deterioration. Damage builds over time and often affects strength as well as appearance – you might not even notice a change in appearance – and is permanent. To reduce risk: avoid displaying originals (as opposed to copies) for any length of time, and use protective enclosures to block light when items are in store.

8) Incorrect temperature: For many chemical reactions, the speed (rate of reaction) doubles for every 10°C rise in temperature. This means that archival materials, which often contain chemicals that are damaging, will deteriorate faster at higher temperatures – in effect self-destruct! Damage may not be noticeable for a considerable time but the impact can be significant and is irreversible. To reduce risk: keep collections in a cool environment.

9) Incorrect humidity: High relative humidity provides the H2O for harmful chemical reactions such as rusting, and decomposition. It also encourages mould growth and insect activity. Low relative humidity can cause some materials to become dried out and brittle. Fluctuations in relative humidity that are sudden, large or frequent can cause swelling, shrinking, stresses, warping and splitting. To reduce risk: maintain a steady, not too damp or dry environment to help preserve items for longer.

10) Dissociation: Loss of value caused by a loss of relevant information or access to that information. Loss of key pieces of a collection, loss of original order within a series which destroys context (for example, if an undated letter goes astray from its proper place within a bundle), loss of knowledge, notes, records or identification labels. It can also refer to material becoming inaccessible – think of floppy discs if you still remember them! To reduce risk: take informed action to preserve a collection, its contextual information, and the knowledge and records that relate to it. Also, ensure good quality labels and write on them with permanent inks so items can always be correctly identified.

for more information right now, visit our trusted sources:



Canadian Conservation Institute

The ultimate source for more than you will ever need to know about the 10 agents of deterioration and their impact on heritage objects!
And a resource from our own website on what to do with water damaged photographs, books and papers, audio or video tapes, DVDs and CDs.

Page updated: 17/11/2020 Page updated by: Ally McConnell

Help us improve Heritage hub

Don’t include personal or financial information like your National Insurance number or credit card details.