This advice will help you protect valuable items in archives and personal collections that comprise single sheets of paper, such as:

• letters and certificates
• newspaper and magazine clippings
• prints and posters
• artworks, such as drawings, watercolours and paintings

Regardless of the material used to produce the images on these objects – such as printing ink, writing ink, watercolour – all such paper-based objects are susceptible to damage or loss through poor handling, poor environmental conditions and poor display conditions.

All materials degrade over time. We cannot stop this process, but we can control how fast it happens. Certain materials are susceptible to deterioration because of their properties. Others deteriorate as a result of particular environmental conditions.

Paper-based materials can deteriorate in two ways: chemically and physically. Types of chemical deterioration include:

• fading of colours and discolouration of papers caused by exposure to ultraviolet (UV) radiation and high lighting levels, age, or contact with certain materials
• deterioration caused by mould attack, which occurs in conditions of consistent high humidity – mould has the ability to consume and stain the materials it grows on
• brittleness of paper caused by acid in the paper or the material the paper is in contact with
• deterioration caused by interaction between the paper and the printing medium used – for example, iron gall ink is acidic in nature and can, over time, burn through the paper it is written on.  

Physical deterioration includes:

• deterioration caused by handling and use, including tears, dents, punctures, abrasions, and losses of portions of the paper item through tearing
• folds and creases causing paper to split, especially if the paper is brittle
• deterioration caused by pest attack – paper and glues are a food source for some insects and rodents
• distortion caused by extreme fluctuations in temperature and relative humidity

As with any archival item, correct handling of flat paper items will aid in preserving them for as long as they are required.

• Handle with care.
• Use clean hands or wear cotton gloves. If cotton gloves are not appropriate, for example if the object is particularly fragile, use clean close-fitting surgical gloves.
• Use a rigid support at all times, especially with fragile items.
• Carry papers flat between two rigid boards, especially over long distances.
• Interleave artworks and documents with archival material to protect them from abrasion, ink or adhesive transfer from other items.
• Use a flat-bed trolley when moving oversized material.
• When working with artworks, use pencil not ink. Pencil marks can be easily removed, whereas inks can be difficult or impossible to remove.

Artworks should be stored flat, and any packaging used such as boxes and folders should be clearly labelled to minimise handling. Make sure storage areas have adequate space for the works to be stored flat. The storage area and facilities should be clean to discourage pests.

Shelves should be made of powder-coated metal. Avoid wooden shelving, as it can release harmful vapours, contribute to the spread of fire and harbour insects. Plan cabinets can also be used to store flat large artworks.

Protective packaging

Store loose flat paper items in simple, protective archival enclosures, as described below.

Paper, card and boards

Materials that are to be in contact with the paper items should be free of acids and other impurities that may damage the item. Such acid-free materials are also known as archival, museum quality or permanent products. These materials come in a range of standard sizes and include boxes, folders, wallets, envelopes, paper sheets and boards.

Boxes are an ideal protective enclosure. They allow paper items to be stored flat, while also providing protection against mechanical damage, light, dust, and rapid changes in, and extremes of, temperature and relative humidity.

Plastics

When choosing a plastic product for storage purposes, it is essential to use a high-quality plastic that is free of plasticisers, surface coatings and other harmful chemicals. The most suitable plastic film is a form of polyester known as PET, which sells under the proprietary names Mylar or Melinex. If these are unavailable then other forms of polyester as well as polypropylene and polyethylene are acceptable.

Encapsulation is often a good method of storage, as it allows the item to be viewed without being taken out of its housing, and takes the majority of handling pressure and abuse. However, heat lamination of artworks is not recommended, as this treatment is not reversible and will lead to the accelerated deterioration of the artwork within.

Valuable paper items should be stored at temperatures between 18 and 20°C and at relative humidity between 45 and 50%. In these conditions the natural deterioration of the objects can be slowed, and in some instances lower temperatures can slow deterioration further. It is important that these environmental levels are stable. Mould will start to grow at around 60% relative humidity, and if the humidity fluctuates more than 10% in 24 hours or the temperature is too high, the items in the collection will become stressed, which will accelerate the deterioration process.

Materials degrade more quickly when exposed to ultraviolet light. Fluorescent tubes that are low in ultraviolet light should be used wherever possible in storage areas. Ultraviolet light can easily be measured with a light meter. Levels should not exceed 75W (microwatts)/lumen. Lights should be turned off whenever possible and storage areas should have no windows, or windows should be covered with curtains or blinds.

Insects and rodents attracted to record storage areas may start eating the records. To reduce the possibility of pest damage:

• do not eat in storage areas 
• keep surfaces (floors, tops of shelves) clean
• check storage areas regularly for outbreaks of insects or rodents. Should an infestation occur, baiting or fumigation may be necessary. See the advice on integrated pest management for further advice on that subject. 
• Insect pest strips can be used as localised insect deterrents. However, the strips should not come into direct contact with individual items.

Before displaying any valuable paper item, a number of factors should be considered. The effects of light, heat and humidity as well as physical risks such as theft and vandalism could endanger the item. Inappropriate display methods or poor quality display materials could also put items at risk.

Lighting

• Avoid direct sunlight.
• Artificial light can also be a source of damaging ultraviolet radiation and heat. Ordinary fluorescent lights tend to have a high UV output unless they are purposely filtered, and incandescent lights can lead to heat build-up. Light sources should be soft and diffuse, rather than direct and intense, and should ideally be 2 to 3 metres away from the display items.

A light meter can be used to measure light levels. Generally, ultraviolet radiation should be less than 75 microwatts/lumen and illuminance should be less than 100 lux. Items that are unstable may require lower lighting levels. Conservators and lighting experts can provide more advice about appropriate lighting systems.

Temperature and humidity

• Ideally, exhibition spaces should be air-conditioned 24 hours a day.
• High temperature and humidity levels can be damaging and should be avoided. Temperature should be maintained at around 20°C and humidity at 50%.

Display materials and method

• The way an item is displayed or mounted depends on the exhibition design. However, the display method used should follow a few preservation guidelines.
• Always exhibit items with some form of protection, such as a frame with glazing, or display case. This will protect the item from dust and dirt and also reduce the amount of UV exposed to the item.
• Items exhibited in frames should be mounted to archival standards, using archival quality materials.
• Use custom-designed supports for oversized items.
• Use chemically inert or archivally sound materials for the construction of supports. Materials to avoid are acidic cardboard, unsealed wood, rubber adhesives, chipboard, polyvinyl chloride (PVC) and sticky tape. Proteinaceous materials such as wool, silk and animal glues should also be avoided as they attract insects.