Guideline 9.3

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Guideline 9.3: The exhibit team carefully considers the scale on which to respond to each Conservation Requirement

What is meant by the scale of response?

A variety of options is available to combat any given conservation hazard. However, in selecting conservation features and strategies to control such hazards an important determinant is the spatial dimension of the response: Will climate controls, for example, be instituted building-wide or focused at the level of an exhibit enclosure or display case?

Within the conservation literature, this range in the scale of response is often referred to as micro versus macro solutions to mitigating hazards, with micro referring to the individualized solution of the exhibit case, and macro referring to controls throughout the wider museum building and environment. In reality there are several levels of response between the level of the case and the building. For instance, there are “zone” solutions within a gallery, in which different conditions are created in different rooms. And at the other end of the spectrum, there is the strategy of creating controlled environments within very small containers that are placed within a larger display enclosure.

For the purpose of mitigating exhibit hazards, the exhibit team should consider the options available at the different levels. These can be broadly categorized into large-scale versus small-scale approaches:

Large scale:

  • The entire museum building
  • The entire exhibition space
  • A room or rooms within the exhibition space

Small scale:

  • An isolated display enclosure
  • A self-contained exhibit case
  • A container within the enclosure or case


Most successful exhibits employ a combination of responses, with certain Conservation Requirements being met at the room or building level and others at the level of the display enclosure. Security features, for example, are often included throughout the exhibit area through staffing and use of cameras; while humidity control, which is not always broadly required, is only installed as needed within specific exhibit rooms or display cases.

What are important factors in deciding the scale of response to the various Conservation Requirements?

Some of the most important factors to consider are:

  • Loan agreements for borrowed objects may dictate the scale of response. Requirements for vulnerable objects may require that those objects be exhibited under specific environmental conditions or housed in climate-controlled cases.


  • Exhibit Plan: For long term exhibits which contain many vulnerable objects, it is often more cost-effective to employ mitigation strategies, such as environmental controls, at the gallery or building level than merely at the case level.


  • The number of objects needing protection may determine the scale on which that protection should be provided. Climate control throughout the area is appropriate when most or all of the objects have similar sensitivity to similar environmental threats. On the other hand, if only a few objects need special protection, they can be grouped together efficiently in a climate-controlled enclosure. And one unique object requiring individualized protection could be placed in a container within a larger enclosure. For example, a collection of an author’s possessions that are vulnerable to theft may be placed inside a vandal proof enclosure; while the author’s clock, which is also vulnerable to humidity and corrosion, could be placed inside a further enclosure such as a plexiglass box equipped with humidity absorbers to stabilize the environment.


  • The most stringent criteria concerning light exposure, pollutants, and acceptable humidity can often be met most effectively and efficiently by using a specially designed exhibit enclosure or display case.


  • Interpretation. The presentation of an historic environment, as in an historical house, requires a “lifelike” display and thus deters the use of cases. Necessary climate control, security, and dust filtration, must be achieved on a building-wide scale or by zone. An exhibit’s interpretive needs may also require that objects be grouped according to style or chronology. Thus they cannot be grouped into cases on the basis of their vulnerability to light or humidity.


  • Expense. Conservation strategies must fall within the available budget. It can be costly to install new ductwork and air handling systems or to upgrade lighting thorough an entire exhibit area. Focusing protection on one room or case may be the most cost-effective solution. Also, whatever strategy is employed, resources must be available to maintain the safeguards for the duration of the exhibit.


An example of scale of response decision-making: Controlling Relative Humidity

Large-Scale Response: Relative humidity can be controlled large-scale throughout the entire exhibit space by means of the building’s mechanical system. Either existing equipment can be augmented, modified or adjusted or additional room-specific HVAC and humidifier units can be installed.

  • The advantage of this large-scale response is that it provides a general level of relative humidity for all exposed objects.
  • The disadvantages, however, are considerable and include: the fact that RH requirements are frequently not the same for all exhibit objects; the expense of procurement, installation, operation, and servicing, which is often great; the difficulty of installing new ductwork and piping in existing structures; and, in winter climates, the increased potential for damage to buildings where higher humidity levels are maintained.


Small-scale Response: Alternatively, the small-scale or localized response to relative humidity control is achieved through a controlled microclimate within enclosures. These sealed enclosures can be as large as a room or walled-off portion of an exhibit or, more typically, an exhibit case.

  • Advantages: This approach is generally appropriate when tight control of the entire exhibit space is impractical for financial or technological reasons, or when only a few of the objects require a more stringent environment. This approach is often cost effective and ongoing energy costs are negligible.
  • Disadvantages: This option requires forethought and careful technical design. Microclimates cannot be created in traditional museum casework and a well-sealed, climate-controlled case must be constructed. Costs of design, construction and maintenance must be built into the project.