Preserving maps and plans
There are a variety of methods for producing maps and plans:
- hand-drawn maps and plans – prepared using inks, pencil, crayons and watercolour paints
- computer-drawn maps and plans – transferred to a hard copy of paper or film, using a line printer
- photoduplicates – made using processes such as blue print, electrostatic duplicating, diazo, and photographic processes
- printed maps – created using modern printing techniques such as offset.
They are created on a range of materials:
- tracing and offset papers
- photosensitive papers and synthetic papers
- plastic film and tracing cloth, which are often used for architectural and engineering plans.
- paper plans are often mounted to fine linen to strengthen them for handling
Preservation and storage
Deterioration of materials over time is inevitable, but we can control how fast it happens. Some materials are susceptible to deterioration because of their composition and others as a result of storage conditions.
- Some types of translucent tracing paper are acidic and deteriorate more quickly because of their manufacturing process.
- Thin papers backed with cloth are sometimes damaged because the cloth and the paper react differently to changes in relative humidity and temperature. The paper may fracture or separate from the cloth, because of the tensions built up between the paper and the cloth backing.
- Starch-filled tracing cloth may be affected by moisture and mould.
- Oiled cloth and paper can become rancid.
- Diazo prints may turn yellow or brown over time. This is due to a reaction between the chemicals used to develop the image and oxygen in the air. Store these records away from light and copy them to another medium if they contain information of long-term value.
Correct handling of maps and plans will aid their long-term preservation:
- The large format of many maps and plans can make them difficult to handle and easy to tear.
- Large format records should be transported flat, supported on an oversized sheet of paper, cardboard or inside a plan folder. These records are often found rolled up and sometimes folded. Folding maps or plans will damage them. If a large format record must be kept in a file, then copy it and put the copy in the file. Store the original plan flat elsewhere.
- If it is necessary to roll them for storage or transport: roll each item around a cardboard tube, longer than the record and at least 90 mm diameter. Use a protective paper wrapping around both the tube and the map/plan.
- When moving large unwieldy items, use flatbed trolleys to fully support them and allow enough flat space for their viewing.
- Carefully unroll large format records, distributing pressure and using long weights to hold the curled ends down. If the curl in the paper is very strong it may need humidifying first and in such a case it is recommended that you seek professional guidance. You can do this through the Agency Service Centre.
- Do not use adhesive tape to repair tears.
- Plastic heat lamination is irreversible and should never be applied to archival records.
Ensure that large format records are free of dust and unaffected by mould or insects before repackaging or placing them in storage. If you find maps, plans and charts with these problems, isolate them and seek advice through the Agency Service Centre.
Protective packaging for maps, plans and charts includes the following options:
- Polyester, polypropylene or polyethylene sleeves – polyester is a tough transparent plastic and polypropylene and polyethylene are cheaper alternatives (if choosing polyethylene, choose a plastic that is around 100 microns thick) – both support plans and protect them from dust and handling damage.
- Interleaving with archival paper sheets protects the records from abrasion, ink or adhesive transfer from other plans.
- Folders that are as large as the plans to provide support and reduce handling of individual records in the drawer.
- Label maps and plans by writing on the back of the item with a soft pencil or if they are individually bagged, attach the label to the sleeve. Accurately list contents on folders and the drawers to minimise handling.
To prevent damage to the records when the drawers are opened and closed the drawers should:
- be fully functional and operate smoothly
- have stops to prevent them from being pulled completely out when they are opened
- have a lip at the front to prevent items from falling onto the floor and one at the back to prevent them from falling behind the drawers
- never be overfilled. Folders should contain no more than about twenty plans. This will ensure that each folder is a manageable size for safe handling.
Other considerations when storing maps and plans are as follows:
- Aisles between equipment should allow easy access to and removal of large format items.
- Suitably-sized tables should be located adjacent to the storage cabinets, so that staff can comfortably and safely check the contents of map folders and retrieve individual items.
Large format records should be stored in the conditions recommended for paper documents and artworks.
If specialised storage is available then temperatures between 18 to 20 °C and at relative humidity between 45 to 50 per cent are desirable. Office air-conditioning generally operates between 21 to 23 °C in temperate climates. If these conditions are stable then the natural deterioration of the objects can be moderated. Wide fluctuations in conditions can physically stress records and accelerate their deterioration. Note that air-conditioning systems often only operate during office hours, leading to a wider fluctuation of temperature and relative humidity at other times. At sustained relative humidities over about 65 per cent, mould growth can occur. It is recommended that you aim for a storage area with stable conditions, where the temperature is around 20 °C and the relative humidity remains below 60 per cent. Materials degrade faster when exposed to ultraviolet (UV) light. Fluorescent tubes which are low in UV should be used wherever possible in storage areas. Ultraviolet light can be easily measured with a light meter, and levels should not exceed 75 µW/lumen. Lights should be turned off whenever possible. Storage areas should not have windows, but if they do they should be covered with curtains or blinds.
Insects and rodents once attracted to a record storage area may start eating the records. To reduce the risk of infestation:
- don’t allow food to be eaten in storage areas
- keep floors, shelves and shelf tops clean
- bait regularly for rodents and fumigate annually for insects, but only fumigate if an infestation is found
- use sticky traps to monitor for infestation and insect type.
Copy maps and plans with a large-format plan copier or scanner with a flat transport path that won’t curl the record around a roller. Fragile or damaged records should be encapsulated before copying in purpose designed polyester sleeves.
Please contact the Agency Service Centre.