This advice is not intended for mould remediation after a large flood incident. We are focusing here on cleaning minor surface mould growth resulting from poor storage environments. Flood incidents have a range of complications that are not covered here
What is mould?
Mould is a generic name often applied to various types of fungi that grow on the surfaces of materials such as fabrics, paper, food and leather. They are multicellular organisms that send filaments through the materials they grow on and produce enzymes to break down their food. Moulds reproduce through the production of small spores which are carried through the air and deposited on surfaces – these spores are in the air all the time and cannot be eliminated from storage areas. Poorly ventilated areas with relative humidity above 60% are more likely to promote mould growth.
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If you find mould growing on any of your records it is first important to determine the extent of the problem.
Small quantities of records can be dealt with fairly easily, but large quantities are usually best left to professional remediation companies. This is both because the work is dirty and repetitive, but also if not cleaned properly the mould can spread and cause more problems.
It is important to determine whether the mould is actively growing before doing any cleaning. What is often termed “active” mould is more difficult to remove and will smear easily. If the mould is active it also indicates that the environmental conditions of the storage area continue to be unacceptable. Relative humidity levels, levels of ventilation and reasons for raised moisture levels should be investigated and remediated.
If you are dealing with a discrete and fairly small outbreak it is preferable to isolate the affected records from the rest of your collection. Place affected materials into plastic bags or air-tight plastic tubs and remove them to a dry, well-ventilated space where they can be assessed and cleaned.
There are also health and safety implications to be considered. Mould can seriously affect your health – people with allergies, respiratory problems and/or compromised immune systems are more susceptible, but everyone should be cautious. Personal protective equipment (PPE) should be worn to ensure that the procedure is safe.
Performing the work in a fume hood is advisable where possible. If a fume hood is not available the space must be well ventilated. Dust masks, plastic gloves, and eye goggles are advised – and ensure that your mask is rated for mould spores (see equipment list below).
Most mould species need high levels of moisture to grow and reproduce. High relative humidity (anything above 60%) will raise the moisture content of hygroscopic (moisture absorbing) materials such as paper, leather, cloth and some glues, which provides free moisture for the mould to grow.
You will need to desiccate the mould by thoroughly drying the records. Reduce the relative humidity either in your storage area or in a designated processing area using a dehumidifier. The humidity will need to be kept below 50% in order to dry the records sufficiently.
Care must be taken when moving mouldy items as the smallest movement can cause spores to generate which will spread the mould through your collection. As mentioned above you must transport the affected material in plastic bags to prevent cross-contamination.
|P3 dust, mist and fume respirator/mask||Occupational Health and Safety suppliers (such as Setons)|
|Plastic gloves (Nitrile are best)||Mediflex Industries, Pharmacies|
|Butcher paper||Artists’ supply store|
|Container with lid or sealable plastic bags (for disposing of used swabs)||Recycle a glass jar, zip-lock bags|
|HEPA filtered vacuum cleaner||HEPA filters can be fitted to many brands of vacuum cleaner|
|Methylated spirits or Ethanol||Hardware store|
|Dehumidifier (optional)||Munters or other flood salvage companies|
|Fume hood (optional)||Laboratory supply companies|
Once thoroughly dry, mouldy records must first be vacuumed with a HEPA (High Efficiency Particulate Air) filtered vacuum cleaner capable of filtering particles down to 0.3 microns. The filter ensures that the spores are not re-circulated around the room. Do not use the brush attachment that comes with the vacuum cleaner as it will get dirty and hold the spores. Instead, use a soft brush such as a paint brush or shaving brush to brush the dust and spores into the cleaner nozzle (brushes should be cleaned with soap and hot water at the end of each day). Use small brush movements towards the vacuum nozzle to ensure that it captures disturbed debris.
Work on a clean, flat and un-cluttered surface. Working on Butcher paper is a good idea as it can be replaced regularly when it gets soiled preventing re-contamination.
Great care must be taken not to get too close to the surface causing it to be ‘sucked’ up. This can cause serious damage – tears and losses. To reduce the suction you can reduce the size of the nozzle by using flexible plastic tubing stuck into the end of the nozzle. Paper strength can be severely reduced by mould damage – if the paper seems pulpy, friable, or the surface is more fibrous than normal, do not use a vacuum. Seek further advice from a conservation specialist.
It is highly advisable to verify the efficacy of your cleaning by getting the objects clearance tested. This involves taking surface samples from the objects and having them tested by a mycological expert. It is also advisable to have air-conditioning systems tested.
Shelves where mouldy items were stored will need to be thoroughly cleaned before the items can be returned to the shelves. Shelves should be vacuumed thoroughly and then damp wiped with a 70/30 solution of Methylated Spirit and water. Allow the shelves to dry thoroughly before returning records.
After cleaning, items should not return to storage conditions with high relative humidity, as there is a good chance the mould will return. Guidelines and Standards on the storage of records are available on the Government Recordkeeping section of our website at Advice or Standards. These publications provide information on the environmental conditions required, types of shelves that should be used, and protective packaging for different record types.
The most important factor to preventing mould is moisture – mould cannot survive without adequate moisture. Relative humidity must be kept below 60%. The Image Permanence Institute published a Preservation Calculator which provides an indication of how well your storage conditions are preserving your collection. An important part of the Calculator is its indicator of the “Days to Mould Germination”. You can download the Preservation Calculator to help you work out whether you have a problem.
Dirt, dust, and food debris provide additional food sources for mould growth so keeping storage areas clean is very important. Shelves and records should be cleaned on a regular basis.
Records should not be packed too tightly as this allows pockets of stagnant, damp air to develop and prevents good air circulation. Do not stack boxes, volumes or other records against walls – especially external walls.
Inspect your records regularly for signs of mould as it is much easier to deal with small outbreaks and any mould growth will indicate potential problems with your environmental conditions.
Further Reading and Information
Florian, Mary-Lou, Fungal Facts: Solving fungal problems in heritage collections.Archetype Publications, London, 2002.
North East Document Conservation Centre Preservation Leaflets provide information on a variety of conservation techniques and issues. Of particular interest for mould are Leaflets under the Emergency Management heading.
The National Archives of Australia has a range of information about preserving records.
The State Library of NSW has a Dealing with Mould factsheet avaibable on their website.
The Australian Institute for the Conservation of Cultural Materials (AICCM) is the peak professional body for conservators in Australia. Their website provides information and links useful for a range of conservation issues.
There are a number of mould remediation companies across Australia. Contact us or your nearest State or Federal archive for further information.
This content was first published on our Archives Outside blog.