Air in the archive…

The Borthwick Institute for Archives, in York, boasts thousands of precious old documents — and closely monitors air quality to hold back the ravages of time.

A huge, modern building outside York holds a treasure trove of the past. Church records reaching back to the 13th century, the local NHS archive and the papers of renowned chocolatiers Rowntree’s and Terry’s are carefully stored alongside colonial history, natural history and the papers of leading figures in theatre, film and TV — from playwright Sir Alan Ayckbourn to comedian Frankie Howerd. All of this needs to be diligently preserved, which means closely monitoring and controlling the air.

While air conditioning systems are usually installed to benefit the people inside a building, at the Borthwick the collections come first. ‘I suppose that is a bit weird,’ laughs Gary Brannan, Keeper of Archives and Research Collections. ‘When people book a slot in our reading room, we advise them to bring a jumper. Even then, we sometimes get complaints that it’s too cold… and we’re strangely popular in summer!

‘Records made on organic materials — such as paper or historic parchment —- all require temperatures of 16℃  to 17℃ and 50% to 55% humidity,’ Gary continues. ‘They degrade at different rates: 13th century parchment turns out to be much more durable than 20th century newsprint. Photographic materials such as glass slides, prints and negatives need cooler, drier conditions. Preservation really means managing the process of decline. You can’t stop or reverse something ageing but you can slow it right down. We call it “arresting the effects of time”.’

There are strict rules on how to conserve such cultural heritage, set out in British Standard BS EN 16893:2018. Indeed, Section 5.4 is all about air quality.

‘The main issue is that changes in temperature and humidity puts stress on the collections and speed up degradation,’ explains Gary. ‘Our building is designed to be thermally efficient, with a lot of thermal inertia, so we often have days where the temperature and humidity remain the same even without our air-handling kit coming on. We’re also continually logging conditions in our storage and research areas. Alerts go off if temperature or humidity are out of line.’

Temperature and humidity are not constant throughout the building, which presents practical challenges. ‘We have a special cold room for storing photographic material. If someone wants to view an item, it’s transferred to one of our strong rooms — but if you do that too quickly, there’s a risk of condensation building up, which will ruin an old, fragile photograph. It needs 24 hours in controlled conditions to slowly come up to strong-room temperature.’

Yet there are benefits from such variations. ‘I don’t think it was an intentional part of the design,’ says Gary, ‘but there is slightly higher air pressure inside the strong rooms than outside, which means a constant flow of air under the door. We find that that helps keeps down dust because it’s simply blown out through the gap. It would also make it harder for any pests trying to get in.’

The designed features include being able to filter out external particulates from the air. ‘Our location outside the city means that isn’t often an issue. Sometimes, around Fireworks Night in the city, the smoke and particulates aren’t entirely filtered out of the air and our system will sound an alarm. That just shows how sensitive it all is.

A more pressing danger is mould. ‘That only needs a little warmth and wet, especially in spring and autumn. You can’t get rid of mould entirely but you keep it inactive with the right atmospheric conditions.’

Even so, care is taken to ensure that this isn’t an entirely sterile environment. ‘You can get important contextual information from the way different materials smell, which you don’t want to lose,’ says Gary. ‘The archive from a hospital will often have a whiff of soap, the records from Rowntree’s have a tang of stale chocolate and there are records related to individuals with a characteristic trace of pipe-smoke. That’s useful for checking if something’s authentic.

Is there any danger from the chemicals that such items release into the air? Gary laughs again. ‘There’s a well-known book among archivists, Dust — The Archive and Cultural History by Carolyn Kay Steedman (Rutgers University Press, 2001), which suggests we all go mad in the end because we’re always inhaling anthrax spores. I couldn’t possibly comment! We’ve been thinking about installing detectors for volatile organic compounds (VOCs), though they’d probably be in trace amounts given the size of our rooms. But we’re always on the look-out for particular volatile chemicals.

‘Most archivists are very attuned to smells as early warnings, just like you might smell smoke and think “fire”. The ageing process releases certain chemicals: the slightly vanilla scent you get from old books is caused by the breakdown of a chemical called lignin in the wood pulp when exposed to air. It turns the paper yellow, too. We control conditions here in such a way that you don’t often get that smell from any of our items — but we’re alert for it.

‘The smell of vinegar, like a chip shop, is an important warning that film stock has begun to break down and needs urgent attention. And we check old cans of film to see if they’re marked “N” for nitrate, which was also used in old photograph albums as a covering for photos. You can be thrilled to find some rare, lost film or lovely looking picture album from the 1920s — but it’s literally explosive!’ The building has, of course, been designed with fire safety in mind.

What about the other way round — do people in the building pose a threat to the collection? ‘Our stores are so big that you need a lot of people in there to affect the humidity, but we can see from environmental monitoring the effect of a large tour group in our strong rooms. The automated systems respond to that as needed.’ What about in handling documents? ‘Really, the damage we try to guard against is mechanical, such as someone accidentally tearing a page. If we’re worried that breathing on a particular document might damage it, we wouldn’t have it out for handling.’

What else could the Borthwick be doing? ‘If budgets and technology could bend to my will, it would be useful to have differing temperatures and humidities in different parts of the same strong room. At the moment, we need a separate room for photographs.

‘More realistically, a richer network of monitoring points would help us better understand what the air is doing. We already take spot readings and move data loggers around to get a better picture. But, for example, our shelves automatically space themselves apart each night at 7pm to get some airflow capacity around them. If the air only comes in from one point in the room, the shelves nearest that point will get more airflow. I’d like to understand that kind of thing better and what can be done to even things out.’

That’s a thought, isn’t it? The more we understand air quality, the better we’re equipped to arrest the effects of time…