Museums need to maintain appropriate and stable environments to protect and preserve their collection. Conditions in both exhibition and storage areas need to be modified and monitored wherever possible to ensure the safety and preservation of collection items.
This Help Sheet introduces you to some of the aspects of museum environment which need to be taken into consideration. These include
- Dust and other pollutants
- Levels of light, both natural and artificial
- Temperature and humidity
This Help Sheet should be read in conjunction with Help Sheets on Storage and handling, Cleaning in museums and Housekeeping Schedule.
As described in the Cleaning in Museums Help Sheet, dust is made up of dirt, soil, soot and salt from the natural environment and human skin and hair which collect indoors. Build up of dust is a common problem in museum environments and it can cause significant damage. Dust is abrasive, it absorbs moisture and other pollutants and it causes staining and other physical damage when it collects in a large mass. To maintain a dust free environment, use the following precautions:
- Vacuum regularly
- Use doormats and dust covers
- Make sure windows and doors remain closed when possible and have effective seals
- Keep items off the floor
- Maintain a regular cleaning schedule: see Housekeeping Schedule Help Sheet
Light is made up of three aspects — ultra violet radiation (UV light) at one end of the spectrum, infrared light at the other end and visible light in the middle. All impact upon collection items. Excessive light and heat cause damage. Visible light determines comfort and visibility for visitors.
When thinking about lighting you need to consider whether it is too bright and whether it is creating too much heat. Reducing bright UV light will limit fading; reducing infrared light will limit heat damage.
The museum environment is usually lit by a combination of natural light from windows and doorways, and artificial light. Sometimes indoor exhibitions are lit by artificial light alone. Outdoor displays of items such as large machinery as well as any interpretative signage are subject only to natural light, unless they are lit up at night.
Natural light varies depending on the time of day and the weather. It is frequently too bright and areas directly under windows can become very hot in sunny weather. Indoors you can control brightness and heat by using window coverings such as curtains and/or indoor or outdoor blinds. In some cases museums choose to cover windows with panelling and rely only on artificial light.
If your display is outdoors, you will have more trouble avoiding natural light. Large objects can be placed in shaded areas or under a built shelter, but the amount and direction of light to which they are subjected will change as the day progresses. You will need to make sure that any outdoor signage is fade resistant.
Artificial light can be controlled and adjusted more easily indoors through careful choice of the type of lighting and planned placement.
Type of lighting:
- Always choose low UV or UV filtered globes that are low voltage so they will not produce too much heat.
- Fluorescent lighting is most commonly used for general illumination of entire museum spaces. UV filtered fluorescents are available.
- Low UV track lighting can be used to highlight certain features.
- With overhead lighting seek a balance between protecting objects on long term display and allowing visitors to move about and view displays easily. If it is too dark, they won’t be able to see where they are going, they will feel uncomfortable and it might even become an occupational health and safety issue.
- Take particular care when using lighting close to objects. Don’t place lighting inside display cases because the enclosed globe will generate intense heat. If you need to put a light inside, use a low voltage, low UV light operated by a timer switch which will only turn on for a short time.
- Use screens or covers to protect objects and create a bit of mystery. Put text on a screen asking a question and prompting your visitor to open the screen to find out more or to see the hidden object.
3. Temperature and relative humidity
Temperature, as everyone knows, refers to heat or cold and it is dependent on the time of year and the location of your museum. However as you do at home, you can control the temperature in the museum environment through various simple methods. The ideal temperature for a museum is somewhere between 18° and 22° C but obviously in some environments this is never achieved.
Relative humidity is a measure (given as a percentage) of the amount of water vapour in the air at a particular temperature. Humidity and temperature are connected and increased temperature can mean increased humidity because the warmer the air, the more water vapour it can hold. The ideal level of relative humidity is between 45% and 55%.
Effects of heat and humidity speed up chemical and biological decay. In particular rapid fluctuations in either temperature or humidity can cause damage. Damage can be physical such as objects cracking or splitting, expanding, contracting and/or becoming warped. Remember what happened to your old cassette tapes if they were left in the sun in a hot car! Warm and moist air is also attractive to insects and moulds and both thrive in such conditions.
What you can do about it
Prevention and reduction are the key words. While you can’t change the weather, you can limit its impact.
- Curtains and blinds: Light and heat are intimately connected. You can use some of the same techniques to maintain an even temperature in your museum as you do to reduce light. External blinds are particularly effective in reducing excessive heat generated through windows. Internal curtains and blinds also help. Keeping doors and windows closed wherever possible will also reduce the temperature in summer and maintain warmth during winter.
- Air conditioning: If this is available in your museum, it will help to retain an even temperature. However air-conditioning can also create problems. Evaporative air-conditioning adds moisture to the air while refrigerated air-conditioners remove it. Dust and other pollutants can also enter through air-conditioning systems so filters need to be checked regularly and cleaned or replaced. You also need to monitor the air temperature. Turning an airconditioner on in a display or storage area when the museum is open and off when it’s not is a problem because the environment is only controlled some of the time. To be effective airconditioners should be run around the clock. This is why they’re not commonly relied upon in small museums.
- Heating: Museums are heated for the comfort of visitors rather than for the protection of collection items. Heat will dry the air by lowering humidity; excessive heat will cause physical damage as described.
- Maintenance and repair: As in homes, insulation in the walls and ceilings will help to maintain a more even temperature. Repairing cracks and leaks in walls, dealing with salt damp and other moisture problems and cleaning gutters will reduce fluctuations in temperature and humidity.
- Careful choice of storage and display areas: Remember that rooms in the centre of the building, at a distance from the outside environment will be the least affected by changes in the weather and therefore the most stable in terms of temperature and humidity. The centre of such a room on the ground floor would be the best place to display fragile items. Avoid storage and display areas that are near water sources, such as under overhead pipes or adjacent to a functioning kitchen or bathroom.
- Layers of storage: The more protected an item is from the outside environment the better. Think about the number of layers there are between an item and the external environment. For example, an item on display inside a case is better protected than one on open display. It has its own microclimate within the case. Similarly, a document kept inside a mylar envelope, placed inside an archival storage box, and sitting on a covered shelf in a quality storage area, has four layers of protection between it and the external environment.
Monitoring temperature and humidity
Accredited museums need to monitor temperature and relative humidity. This can be done using various types of equipment. The most common is a Thermohygrograph which measures both. Digital monitors or data loggers that download data to a computer are also readily available and these provide accurate and timely results.
Unfortunately museums are very attractive places for insect pests to hang out. Numerous types of beetles, moths, ants and borers find items in museums irresistible. They love dust especially human skin and hair which gathers indoors. They also like to get their ‘teeth’ into objects which are fragile and can easily cause serious and irreversible damage.
Getting rid of an insect infestation is much harder than preventing one. The use of chemical pest treatments is generally not advised as they may not kill insects at all stages of their lifecycle and may leave harmful residues. It is therefore essential that museums use preventative measures. Many of these measures are the same as those used to manage dust, temperature and humidity. Museums are also encouraged to implement an Integrated Pest Management program to reduce the incidence of pests and prevent the damage they cause. Please refer to the Help Sheet on Integrated Pest Management for detailed information about implementing this type of program.
A few simple ways to discourage pests
- Cleanliness and good housekeeping practices: Make sure that you have a regular routine for vacuuming. This will remove dust and other attractions for pests as well as suctioning up insect eggs, larvae and the insects themselves.
- Repair and maintenance: insects love cracks and crevices that they can hide in. Make sure to fill and seal any cracks in walls and fasten loose skirting boards and deal with any leaks.
- Careful storage: think about creating physical barriers to prevent pests from reaching museum items. The layer approach mentioned above which is used to protect objects from the external environment is also appropriate for preventing pest access.
- Keeping windows and doors closed and checking door and window screens and seals will also help prevent pests entering the premises.
- If you discover pests, try to identify them and remove them carefully before they do further damage. Seek the expert advice of a conservator before using any chemical products to destroy them.
. For more about light see ‘Light and ultraviolet raditation’ in ‘Damage and Decay’ volume of Heritage Collections Council, reCollections: caring for collections across Australia, 1998, p. 3-17.
 See chapter on ‘Humidity and temperature’ in ‘Damage and Decay’, Heritage Collections Council, reCollections: caring for collections across Australia, 1998, p. 19-37.
 ‘Humidity and temperature’ p. 23
 ‘Humidity and temperature’ p. 27-28