Choosing new display cases

When it comes to choosing a display case, visibility and access for the public isn’t all that matters. Choosing the right kind of display case is also best practice for preventive collection care to protect and secure collections or maintain ideal environmental control.

There are four different kinds of display case used in museums.

These are:

• Conservation grade cases
• Ventilated cases or dust covers on plinths
• Standard cases
• Designer-built cases

Conservation grade criteria

Conservation grade cases provide the ultimate protection for items. Achieving this classification requires the method of construction and materials used meets the following criteria:

• Be sealed from airflow, with an air exchange rate of less than 0.1 per day. (The Government of Canada provides more detailed guidance on measuring the airtightness of display cases in a technical briefing.)
• Be made from chemically stable materials and avoid wood or wood composites such as medium density fibrewood (MDF), which can harbour pests or emit harmful substances.
• Allow for relative humidity control to create stable microclimates.
• Include options for controlling internal pollutants.
• Avoid internal heat sources such as lighting.
• Incorporate ultraviolet (UV) filtering through materials or design.
• Provide appropriate security, including locks, alarms, and glazing compliant with Government Indemnity standards.

When to choose conservation grade cases

Conservation grade cases are essential for any items that require tightly controlled environments. Especially in rooms where environmental conditions change often such as open windows, public access, or higher pollutant levels such as museum foyers or city-centre buildings. These sealed cases protect items against changes in relative humidity, air pollution and theft.

Examples of items that might require controlled display environments include:

• Some metalworks, especially archaeological artefacts
• Some composite objects, such as feather headdresses
• “Weeping” glass
• Weak or deteriorated objects
• Organic materials, such as wood from archaeological finds
• Chemically unstable items, such as celluloid nitrate or geological specimens

This list is not exhaustive. If you are in any doubt about items from your collection, contact a conservator through the Institute of Conservation (ICON) website.

Long term investment

Conservation grade cases are extremely durable. The high quality of their material and controllable environments means they can be used to display a variety of items. Museums may request that you use a conservation grade case when lending you items from their collection.

Ventilated cases are deliberately unsealed to allow constant airflow while still offering some protection from handling. This helps prevent the build-up of pollutants around objects and makes them a more affordable option than conservation-grade cases.

To ensure effective ventilation, vents should be at least 2 cm long. However, airflow also allows dust to enter, so cases require regular cleaning, and care should be taken when removing objects. Only clean the case using appropriate materials that will not damage either the objects or the case itself. Increased handling also raises the risk of damage. Further guidance on handling objects is available in the Introduction to Collections Care guide.

When to use ventilated cases

Appropriate conditions for using a ventilated case are:

• When objects aren’t sensitive to relative humidity fluctuation, pollution or dust, such as objects made from glass, stone, and ceramics.
• In indoor environments where the conditions are already monitored and controlled, for example through air conditioning.
• If you have trained collections care staff available to manage and maintain them.

Customised cases

If you don’t have the funds available for conservation grade or ventilated cases then standard or designer-built cases are the next best thing. Standard cases come in a range of materials and it’s important to choose the right one for your collection.

Materials you can use

Some materials are safe to use in any kind of case.

These include:

• Metal, preferably baked enamel or steel on aluminium
• Glass
• Perspex
• Neoprene, which is used to seal cases

Other materials can be used, but as its dependent on the material/s to be displayed make decisions after consultation from a conservator.

Check before using:

• Woods such as yellow pine, spruce, walnut, elm or magnolia
• Acrylic latex emulsions and epoxy resins
• Hot melt glues (ethylene/vinyl acetate copolymer types)
• Some new polymer boards, tested for stability by independent laboratories

Materials to avoid

Many materials are too chemically unstable and will react badly against items from your collection. his risk increases in unventilated cases, where pollutants and harmful chemicals can build up.

Materials you should avoid using in display cases include:

• Many kinds of wood, including oak, teak, and more
• Most composites, such as plywood and Medium Density Fibreboard (MDF)
• Adhesives and sealants containing acetic acid or formaldehyde

 Always speak to a conservator or a reputable case designer before buying cases that could potentially damage your collections.

It’s possible to customise display cases to better control their environments.  If you are unsure if your case might be damaging collections or if it is environmentally ‘leaky’ you can do some tests first before you spend money on any improvements.

• You can check fabric and materials to see if they have passed Oddy Test
• You can set up environmental monitoring inside the case (by purchasing or loaning loggers) and comparing with external readings for temperature and RH to determine your air exchange rates.
• You can remove heat emitting and UV producing lighting

If you’re using a ventilated or standard case, then you can use additional protective measures to effectively preserve your items.

Using laminate foil

If your case is made from wood, cover it in laminate foil. This seals in damaging materials such as organic acids and formaldehyde. Avoid using a lacquer or paint, as they’re proven to be far less effective barriers.  After sealing your case you can add pollution absorbers and humidity buffers. These will only work effectively if the case is properly sealed, as high air exchange rates will quickly saturate them. Pollution absorbers act like sponges and get saturated quickly if they’re used without proper sealing.

Move light sources

Objects can be badly damaged by fluctuating temperatures and humidities, light and UV. Avoid iterior lighting that causes a rise in heat levels inside the case. Using unsuitable light sources can cause temperatures to rise quickly, change the relative humidity, and cause fading in light sensitive objects. It can also increase internal pressure, leading to greater air exchange and dust ingress. Use external lighting where possible to avoid this problems.

If you require interior lighting, separate it from the display area with a glass or chemically stable barrier and provide ventilation for heat. Fibre-optic or LED lighting is preferable, as it produces less heat by transmitting light from an external source.

The Collections Trust provides a wide range of guidance and advice on collections care.

The Government Indemnity Scheme (GIS) advice guide provides more information on how the scheme supports UK museums by providing an alternative to commercial insurance.