This painting was stored for years without protection from insect attack. The extensive array of fly-spots has left permanent visible damage on the face and neck of the sitter. Detail:Georgina McCrae 'Miss Agnes Morison' c.1830 oil on canvas
Why paintings deteriorate
Light, heat, moisture, air pollutants, dust, dirt, insects, physical vibration and impact can lead to slow deterioration of, or sudden damage to, a painting. Paintings in art galleries and museums are kept in conditions which protect them from those things which cause material deterioration.
Light causes chemical changes in many materials used in paintings. The most obvious are the yellowing and darkening of varnishes and the discolouration of certain pigments. Sustained exposure to ultra violet rays found in natural light is the most damaging. Museums and galleries minimise natural daylight and use light which filters out UV to display works.
Temperature and relative humidity
Paintings are essentially layered objects, built up from canvas, ground layer, paint layers and varnish layers. The layers contain materials which have differing physical characteristics including the rate at which they expand and contract at varying temperatures and the rate at which they take up moisture from the surrounding air. A constant climate is therefore the ideal situation for keeping works of art stable. The museum standard temperature for keeping paintings safe is 20ºC ± 1ºC. The accepted museum standard for relative humidity is 50% ± 3%. Fluctuations in temperature and humidity set up cycles of expansion and contraction which will inexorably lead to the deterioration of paintings. Museums and galleries have sophisticated airconditioning systems in place to maintain constant environmental conditions.
Dust, dirt, air pollutants, insects
Dust is composed of minute particles including some hard substances that can scratch paint or varnish if rubbed against the surface of a painting. Some types of dirt, including insect debris, can contain acidic components which eat into the paint surface. Similarly, industrial air pollutants can affect the paint or the finish on a frame. It is important to keep paintings free from dust and dirt and away from air pollutants.
Physical vibration or impact
Many paintings are on stretched canvas which is very susceptible to vibrational forces. Paint loss can eventuate from continual or excessive vibration. Paintings which travel from gallery to gallery are always transported in protective crates with foam padding to reduce vibration from movement and shock. Poor handling can result in severe damage to an artwork. Museums and galleries have guidelines and standards for moving works of art.
Damage resulting from physical impact – image shows a rupture through the paint layers and canvas.
Caring for paintings at home
Most homes are not fitted out to resemble art galleries. Domestic activities such as cooking, bathing and heating produce areas of climate change across the average home. However, there are many strategies you can adopt to keep your paintings as safe as possible.
Stretching and framing
Make sure that your painting is stretched and framed correctly and fitted with a safe hanging system which is appropriate for the weight of the work. Poor stretching can result in an inappropriate degree of tautness and deformation of the canvas support which can exert pressure on the paint layers and lead to paint loss. If it is on a rigid support or unframed, ensure that the hanging system does not endanger the paint or the support. Frames generally protect works of art. It is important that a conservation standard backboard be fitted to the frame. This will reduce damage from changes in the environment, poor handling and airborne pollutants and dust. You may want to protect the surface with a sheet of acrylic or glass. Professional conservators and conservation framers can advise you on specific requirements for your work of art.
Once your painting is suitably framed you must decide where to hang it. Keep in mind the museum conditions discussed and try to emulate them in your home. For example, a painting hanging in a bathroom will be subjected to fluctuating conditions of temperature and humidity. If the moisture content of the air is high enough mould growth will flourish, resulting in disfigurement of the image and in many cases a permanent change in the paint surface. Not all damage is treatable, so it is best to take preventive action and hang your painting away from:
• outside walls
• direct sunlight or spotlighting
• water pipes and splashing
• wet or very dry areas
• high traffic areas such as hallways where contact with the painting may occur
• open fires, gas fires and heating/cooling ducts
• tobacco smoke
• food preparation areas
Moving paintings provides a prime opportunity for damage to occur. Paintings can be wrapped but take care not to place wrapping against the paint surface. The best option if you are going long distances or have large paintings is to use a removal company specialising in art transport. If you have any queries a professional conservator will be able to advise you.
Deteriorated or damaged paintings
If your painting does sustain damage or is in a deteriorated or dirty condition, don’t attempt to repair or clean it yourself. Paint surfaces are especially vulnerable to water and other cleaning agents which may damage them irreparably. Seek advice from a professional conservator.