Friday 25 June 2021

The Enemy in the Archives: Managing Mould

By conservator Catherine Firth

If you arrive at the Borthwick to bring us new material for the archives, one of the first questions we might ask you is “where has this been kept?” We are not trying to be nosy - what we are really asking is what the environment might have been like. If it was in a basement it might have been cold and damp; if it was in the loft it might have been very hot and very cold; if it was stored next to a radiator it might have been quite dry. The most important question for us is whether the records have been damp. This is because mould enjoys living in damp places, and paper, leather and glues offer mould lots to live upon. We don’t want to introduce mould into our strongrooms. 

Mould is a living organism that belongs to the kingdom Fungi. Although they look like plants, they are actually not a plant or an animal. They cannot ‘make’ their own food, as plants do - but additionally they do not ‘eat’ food like animals. Instead they absorb nutrition from other organic substances. To do this, they secrete enzymes, which break down the substance into smaller organic molecules that can be absorbed. Mould uses spores to reproduce, and these can be found all around us. But they need the right conditions to germinate - the spores need moisture, the right temperature and a food source, such as archives. 

Bundle of paper documents affected by mould.

There are many different causes for moisture in our homes. Bathrooms and kitchens are obvious ones, but other occurrences could come from poor ventilation, garages and sheds with no buffer from the environment outside, leaks or even condensation on windows. This is why mould can commonly be found in houses. Unfortunately, as well as damaging our belongings, mould can also be dangerous to our health. Exposure to mould can cause respiratory issues, such as nose and throat soreness, irritation and congestion, and coughing, along with other symptoms if exposure is continued. It can be particularly dangerous to anyone who has existing respiratory problems or issues with their immune system. 

Various documents stained by mould and damp damage.

With this in mind, when we treat mould we make sure we are wearing the appropriate protective equipment. We wear nitrile gloves and face masks to FFP2 or FFP3 standards. For large-scale treatments we would wear goggles. We also have white coats that we can wear over our clothes, so that any spores that might land on us can be removed straight away. We are lucky enough to have a vacuum table in our isolation room, which sucks the air (and hopefully the spores) down and away from our faces while we are working. This, like our handheld vacuum, has a HEPA filter, so when we use the table or the mini-vac we know that the spores are being caught by the filter and not recirculated around the room. We also work in a room with the option of a window, for increased ventilation. 

Mould documents on a perforated air bench waiting to be cleaned. Also on the table are nitrile gloves, a mask, various snake weights, brushes and spatulas.

Our first task is to make sure that the mould is dry and inactive. If it is still slightly damp, and smeary, then the mould is still active and will not be easy to remove. We place dehumidifiers into the room, and fans to increase the airflow, and we air the mouldy material until it is dry and powdery to the touch. Once the mould is dry, it is a relatively straightforward task to remove any spores on the surface with soft brushes over the vacuum table. Sometimes we find that the mould has stained the paper, and this colour cannot always be removed. There are also occasions where the mould has damaged the paper to the extent that it has very little strength left - it can be rather tricky to handle it without causing more damage. We may consider ‘re-sizing’ these papers once the mould has been treated - adding a substance to them such as methyl cellulose or gelatine, to give them some strength back. 

A fragile mouldy document with large losses, opened out to be cleaned.

Obviously the best option is for us to avoid mould altogether! If you can store your important belongings in a cool, dry environment, with plenty of ventilation, then this is ideal. But we do not always have the luxury of these spaces for storage. If you come across mould at home, do take care. For smaller outbreaks, you may be able to manage it yourself. Isolate the item(s) from any unaffected material to prevent the spores spreading, and if you cannot treat it right away then seal it in a plastic bag or container. Ensure the mould is dry and powdery to the touch before attempting to treat it, by airing it well with cool air. Removal itself is best done outside in the open air, with gloves and a mask, and a soft brush. Keep the mouldy material and any treatment processes away from anyone with immune system or respiratory issues. And for any larger outbreaks or valuable items, do contact someone for help and advice - it may not be safe for you to do it alone. 

 Wishing you fungi-free archives!

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