Dealing with mould

One of the most common causes of damage to books, paper and photographic emulsion is mould.  Mould can weaken paper, making it soft and fragile, and discolour and stain paper and leather permanently.

Mould is a type of fungus. Like other fungi, it needs dead or living organic matter for nutrition. Billions of mould spores float in the air, and when conditions are suitable (e.g., high humidity, warm temperature, stagnant air and dim light) they germinate and bloom. A musty odour, stains and furry or downy growth on the surface are very strong indications of a mould outbreak.

Collection material may become mould-affected through water damage due to spills and leaks. More severe cases of mould occur when books have been stored in humid conditions over a period of time. 

Damage due to mould is largely preventable. Storing your collection in clean and stable conditions, avoiding high humidity, ensuring good air flow and monitoring conditions regularly will all help prevent mould outbreaks in your collection.

Health issues

Some moulds pose serious health risks, including lung, skin and eye irritation.  Any handling of mould-affected material should be carried out with the protection of disposable rubber gloves and a mask. HEPA (High Efficiency Particulate Air filter) respirator masks which filter out particles the size of spores offer the best protection. If these are not available, disposable dust masks provide some protection. If you suffer from allergies or respiratory problems you should avoid contact with mould. Treatment, including brushing off dry spores, should be carried out by a professional conservator.

Shelving and clothing contaminated by contact with mould should be washed immediately in hot soapy water, rinsed and allowed to dry completely. Disposable gloves and dust masks should be disposed of safely in sealed plastic bags.

In the past, chemical treatments, including fumigation, were used to kill mould infestations. In most cases this is not recommended now, as the chemicals used may leave hazardous residues on the treated material. Fumigation does not eliminate the need to physically clean the mould off items. Again, this work should be carried out by a conservator.

Procedures for dealing with mould

The following procedures should be carried out at the earliest sign of mould.

1. Deal with mould-affected material as quickly as possible to limit the damage caused and to prevent contamination of other material. Isolate the material prior to treatment by moving it to a dry place.
2. If mouldy items are dry, store them in sealed plastic bags while awaiting treatment. (Inactive mould is dry and powdery.)
3. If mouldy items are damp or wet: remove them to a well ventilated isolated area, rest them on shelving or surfaces protected by waste paper, and allow to dry. Fans will help the drying process. Materials that feel cool or show evidence of moisture need further drying time.
4. When items are dry, clean the mouldy surface thoroughly with a soft brush. This should be done in a fume cupboard, and by a conservator with the equipment to do this work safely.
5. Before reshelving the treated material, make sure that the collection material and the storage area are clean and completely dry. Shelves should be cleaned with hot soapy water, rinsed and allowed to dry completely. Monitor the affected material after the mould clean-up to check for new outbreaks.
Unfortunately, there is little that can be done to remove stains caused by mould, as the stains are unaffected by ‘safe’ stain removal methods.  Mould stains are usually permanent.

Prevention

The best means of preventing mould growth is to deny spores the moisture necessary for germination. A few guidelines to mould prevention are:

1. Do not shelve books or store paper materials directly against an outside wall, as they may become damp. A dividing wall within the house is preferable. Outside sheds, attics, garages and basement areas are also unsuitable.
2. Allow air to circulate between the wall and storage cabinets to enable any moisture to evaporate.
3. Do not over-pack shelves. Allow room for air to circulate.
4. Do not store books or any collection material on the floor.
5. Store your collection where there is a stable environment with limited fluctuations in temperature and humidity.
6. Regularly inspect your collection for mould.
7. Keep the storage area clean and dust-free to minimise opportunities for mould growth. Ensure that any building maintenance work is done quickly to minimise disturbance.

For more information

Fungal Facts: Solving fungal problems in heritage collections – Mary-Lou Florian, Archetype Publications, London, 2002

reCollections, Caring for Collections Across Australia

http://www.bodley.ox.ac.uk/dept/preservation/training/mould/intro.htm

http://palimpsest.stanford.edu/byauth/nyberg/spore.html

The material contained in this Information Sheet is for general reference only and should not be relied upon to change a legal or financial position. The State Library of Victoria does not warrant the accuracy or completeness of the information and disclaims all liability for any loss and or damage that may be caused by reliance upon it.