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Preventive conservation isn't just for museums, but for all works of art. Here are some of the ways your artwork might become damaged and some advice on how to treat these issues.
All light causes irreversible damage to artworks. The extent of the deterioration depends on the type of light source, its intensity and the length of exposure. Light damage is accumulative.
Natural light is an extremely intense source of energy and contains ultra-violet (UV) radiation. Most artworks are composed of organic materials that make them especially vulnerable to UV wavelengths, which cause embrittlement and discolouration. However the visible light spectrum is the main cause of fading to colours rather than UV.
The effect of artificial light is less acute, although fluorescent tubes do emit substantial amounts of UV. Incandescent light sources are the least harmful, but the heat they generate can still, like sunlight, damage an artwork.
Usually the most obvious effect on a picture exposed to too much light is the change that occurs to its colour.
Varnishes on paintings can darken or alter colours too.
Watercolour pigments may fade dramatically in a very short period of time.
The canvas or paper support can become increasingly discoloured and brittle as the light chemically changes the structure, making it weak and inflexible. Light damage is not limited to 'old' artworks. Modern pigments, canvas, colour and black and white photographs can fade or change just as quickly.
What to do
Most organic materials used to make pictures are hygroscopic, meaning they will absorb or release moisture in response to changes in the environment.
Relative humidity is a measurement of the amount of moisture in the air. As the temperature changes, so does the amount of moisture the air can hold. Extremes and fluctuations of temperature and humidity are the most damaging, since they set up a cycle of rapid expansion and contraction, which places the artwork under stress. It is important to control both in order to minimise the effects.
Mould growth will flourish in high levels of temperature and humidity. It creates disfiguring, sometimes permanent stains, attacks the surface of the work, and can digest paper, canvas and paint media.
As artworks expand and contract in response to the amount of moisture in the air, internal stresses are created. This can lead to flaking and cracking in paint layers and photographic emulsions, distortions, and even splitting and tearing of support material.
High levels of humidity and temperature can increase the rate of chemical reaction, effectively speeding up the rate of deterioration of any artwork. Conversely, in very low levels of humidity, paint layers and support materials can become desiccated.
Insects and rodents flourish in a warm, damp climate and enjoy nothing more than chewing their way through your valued watercolours and photographs.
What to do
The mild, wet climate in New Zealand provides the perfect breeding ground for insects and mould.
Insects will attack artworks in a variety of ways, resulting in a range of damage. This may be visible as small holes restricted to a frame or stretcher or as spot stains on the surface of an artwork. In the case of artworks on paper or photographs, however, extensive losses to the image and support are quite common.
While insects and rodents will thrive in an undisturbed dark, dusty environment, mould requires a damp atmosphere.
Dust is always present in the air. In direct contact with the surface of artworks, it is not only disfiguring, but also abrasive.
Silverfish will eat paper and, in the case of photographs, the gelatine layer which comprises the image.
Borer can destroy frames and stretchers on paintings internally. As a result the damage is not often recognised until too late.
Flyspots, commonly seen on the surface of paintings, are small dark deposits left by flies. The can etch into paint and varnish layers, permanently disfiguring the image.
The brown spot stains on watercolours are known as 'foxing'. They are usually caused by metallic impurities in the support paper or backboard, and are often associated with surface mould growth.
What to do
It pays to have artworks correctly framed. Framing reduces the possibility of damage from handling and provides protection against the environment. Because an artist will often choose the original frame to complement the artwork, the aesthetic impact of alterations should be carefully considered.
Acids damage paper. When cheap boards, glues and tapes are used in direct contact with paper, they can make it acidic, discoloured and unstable. Such materials are often very difficult to remove, leaving the artwork severely damaged and permanently stained.
If paintings on canvas lack a backboard, they may suffer from impact damage and an accumulation of dirt on the reverse.
Glazing is useful protection for both paintings and works of art on paper, but can adhere to artworks if in direct contact.
What to do
Regardless of the value of an artwork, it is often irreplaceable to its owner. It is vital that paintings, works of art on paper and photographs be cared for if they are to last. Many factors influence the permanence of artworks.
Sometimes there are inherent problems due to the quality of the paint, canvas or paper used; alternatively a combination of incompatible materials in the artwork may promote instability. More often, careless handling, poor framing and inappropriate methods of display and storage contribute the most damage.
It is important to consider the environment in which you keep your artworks. Our everyday climate has levels of light, heat, moisture and pollutants which can produce destructive chemical and physical reactions within works of art.
Although it is not usually possible to prevent deterioration completely, modifying the environment will help to slow down the process of decay. This is good conservation. By taking a few simple steps now, you can significantly aid the preservation of your art works. Remember, not all damage is reversible – prevention is always better than cure.
We offer advice and practical treatment for paintings and works on paper through our Conservation Research Centre. Trained conservators are also available to survey both private and institutional collections.
Preventive conservation is not only suitable for museums, that is why Artcare: the care of art and artefacts in New Zealand was produced.
Our conservators and specialists from around the country wrote Artcare, and it is intended for individual collectors and small museums without conservation staff. Please note that the list of suppliers published in Artcare may be out of date. Read this publication online.