Conservation of the NGV Collection requires a multi-pronged approach from tailored care for individual artworks to large-scale measures, such as controlling the gallery environment, to enhance the longevity of the entire Collection. The NGV Collection includes artworks made from a range of materials including furniture and frames with inlaid and veneered decoration, illuminated manuscripts on parchment, early colour photographs, silk textiles, polychrome wood sculptures and paintings on bark. These works all respond to Relative Humidity (RH)The amount of water vapour in the air as a percentage of the maximum amount possible at that temperature. The higher the temperature, the more water vapour the air can potentially contain. and temperature (T) and exposure to visible and ultraviolet (UV) light.
Relative humidity is the amount of moisture present in air. It is expressed as a percentage of the amount of moisture the air could hold if it were saturated. Air at 50% relative humidity holds half the maximum amount of water possible at that particular temperature whilst air at 100% relative humidity holds the maximum amount of water possible and is said to be saturated. Relative humidity and temperature must be kept at stable and optimal levels in order to avoid damage to the works. If relative humidity is too low, materials can dry out, too high and they can swell, and there is the potential for mould growth and metal corrosion. At NGV, relative humidity is maintained within a range between 40–60% RH to mitigate these risks while also being comfortable for our visitors and staff.
Because RH and temperature are inter-related (warm air can hold more moisture), it is also important to control temperature. The temperature at NGV is comfortable for people without being too warm, in a range between 15-25°C. Excessive heat can not only lead to decreased RH, it can also accelerate chemical reactions and physical change that lead to degradation of the artworks.
Rapid changes in temperature or relative humidity can cause sudden movement in materials (expansion and contraction), so it is important to constantly monitor the gallery environment and ensure the relative humidity and temperature are stable. This presents a challenge for conservators when an artwork is made of various materials, all responding in different ways, creating stresses that can lead the physical damage such as distortion and cracking.
Since the nineteenth century, NGV staff have carefully monitored and maintained the gallery environment and over time, as technology and knowledge have evolved, so has our approach. Today, we are actively embracing new technologies and undertaking research to ensure the gallery environment is maintained sustainably into the future.