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Conservation Tip No 5: Removing mould from records and archives

Removing mould from records and archives

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 not covered here.

What is mould?

White, fluffy mould like this is common on volumes and records

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. Given the right conditions these spores will germinate and grow.

Before you begin

Removing mould can be difficult, dirty and time consuming. Mould remediation should not be undertaken lightly – especially where large quantities of records are affected.

If you find mould growing on any of your records it is first important to determine the extent of the problem.

Small spots of mould indicate poor storage conditions. The mould should be cleaned and the conditions rectified as soon as possible!

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.

Mould left unchecked or poorly dealt with can devastate collections leaving them close to useless. Good environmental conditions are crucial to preventing mould growth.

It is important to determine whether your mould is dead or alive before doing any cleaning. Live mould is more difficult to remove and will smear easily. If the mould is alive it also indicates that the environmental conditions of the storage area continue to be unacceptable.

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 cleaned.

Your health and safety

There are also health and safety implications to be considered. Mould spores whether they are dead or alive can seriously affect your health – people with allergies and/or respiratory problems are more susceptible, but everyone should be cautious. Personal protective equipment (PPE) should be worn to ensure that the procedure is safe.

Nitrile gloves and dust masks are required when cleaning mouldy records. Methylated Spirits and water solutions can be used to clean shelving

Work should be carried out in a well ventilated space and using a fume hood is advisable where possible. Dust masks, plastic gloves, and eye goggles’ are advised – and ensure that your mask is rated for mould spores (see equipment list below).

Drying your records and killing the mould

Most mould species need high levels of moisture to grow – without moisture they will die. 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.

To kill the mould on your records you will need to reduce the amount of moisture available to the mould to grow. You can either reduce the relative humidity in your storage area by using devices such as dehumidifiers, or you can remove the affected records to a clean, dry space. 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.

To confirm the mould is dead brush the surface of the mould with a small brush – if it is powdery it is likely to be dead. If it is slimey or smears – it is likely still alive.

Equipment and materials required for cleaning mouldy records

 

Brushes and vacuum nozzle fitted with flexible rubber tubing

Checklist: Supplier:
P2 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
Rubbish bags Supermarket
HEPA filtered vacuum cleaner HEPA filters can be fitted to many brands of vacuum cleaner
Methylated spirits or Ethanol Hardware store
Wiping cloths
Dehumidifier (optional) Munters or other flood salvage companies
Fume hood (optional) Laboratory supply companies

Mould removal procedure

Once thoroughly dry, mouldy records must first be vacuumed with a HEPA (High Efficiency Particulate Air) filtered vacuum cleaner. 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).

Brush the mould into the vacuum nozzle. Muslin can be placed over the nozzle to reduce suction

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, muslin or ‘pantyhose’ material can be stretched over the end of the nozzle with an elastic band (this also prevents the paper from being sucked into the machine). An additional safeguard is to reduce the size of the nozzle by using flexible plastic tubing stuck into the end of the nozzle.

Before returning records to storage

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 wiped with a 70% solution of Methylated Spirit or Ethanol. 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. State Records provides Guidelines and Standards on the storage of records on its website. Look under Government Recordkeeping Manual and then Guidelines or Standards. These standards provide information on the environmental conditions required, types of shelves that should be used, and protective packaging for different record types.

Preventing mould

To prevent mould growth on records you must keep your storage areas clean and dry and provide good air circulation.

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 carefully dusted 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 State Records NSW or your nearest State or Federal archive for further information.

  • Robert Mills says:

    Hi

    Just wondering if the brown ‘foxing’ that can sometimes appear on old photos (and documents) is a form of mould ? and if so how to go about combatting it. I am keen to know if it can be reversed/removed especially from old pix.

    Cheers

    Robert M

    June 25, 2010 at 1:30 pm
  • Elizabeth Hadlow says:

    Dear Robert

    “Foxing” is a generic term used to describe a range of deterioration mechanisms in paper and photographic documents – the thing they have in common is that they all tend to appear as small brown spots. Some “foxing” is almost certainly caused by the action of mould or mildew as enzymes used by the organisms breakdown the structure of the paper or photograph. The brown staining is caused both by the residual dead mould or mildew and also the deterioration of the substrate. Other forms of “foxing” are caused by imperfections in the paper – for example metal inclusions from the manufacturing process will cause corrosion staining that often appears as small brown spots. In photographs it is possible that some spots possibly referred to as “foxing” are caused by poor processing. In some situations it is difficult to determine the underlying reason for the spots.

    “Foxing” is very difficult to remove. Some spots can be reduced by the aqueous treatment of the document or photograph, however these treatments do pose a risk to the item and must be undertaken in a controlled environment by specialist conservators. Some people advocate the use of peroxide or sunlight bleaching to reduce or remove foxing spots in paper documents – however bleaching is a risky treatment for most items to undergo and there is evidence that the spots are not removed permanently – returning after a number of years.

    The best way to avoid documents becoming foxed is to store them well. Storage areas must be cool, dry, dark, clean and well ventilated. Humidity is a known contributer to the foxing of most materials and should be kept within the range of about 45-60% at normal room temperatures of about 18-22 degrees. This reduces chemical action in the material and also reduces the risk of mould growth. Photographs must be stored in enclosures that comply with the Photographic Activity Test (PAT) which will ensure that the enclosure will not adversely interact with the photograph – there are number of conservation suppliers who can provide such enclosures.

    The following publications and websites are a good places to start if you are interested in reading more on this subject:
    * http://www.aiccm.org.au – website for the Australian Institute for the Conservation of Cultural Materials
    * Reilly, J. “Care and Identification of 19th Century Photographic Prints”, Kodak
    * http://cool.conservation-us.org/ – online resource operated by the Foundation of the American Institute for Conservation

    I hope this is of some help

    regards
    Elizabeth

    June 28, 2010 at 2:22 pm
  • Robin Cecil-Wright says:

    Thank you for a no nonsense well researched article.
    I recently found some white mould on some of my
    paintings.
    There is so much rubbish on the internet, you don’t have to be a fly to be caught !
    If ever there was a page that deserves a book mark – this is it.

    Robin

    October 1, 2013 at 3:41 pm

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