Oil paintings can be maintained for years of use and enjoyment provided that some basic care and attention is given to their preservation. By avoiding the following basic causes of damage, your art can by enjoyed for many generations to come:
The basic causes of damage are:
Excessive high light levels
Extremes and fluctuations in temperature and humidity
Excessively high light levels can cause fading and/or darkening of paintings. In order to avoid light damage, fine paintings should be displayed in dim areas where no direct sunlight is allowed to fall on them. The suggested light level for paintings is 200 lux. Light levels can be measured using the light meter in a 35-mm camera.
High light levels also can cause damage due to excessive heat build up. Avoid positioning lights too close to the paintings, such as lighting mounted to the frame or directly above it. Diffused spotlights should be mounted at least 10 feet from the painting to avoid potentially damaging heat buildup.
Temperature and Humidity Levels:
Extremes and fluctuations in temperature and humidity can cause damage to paintings due to the expansion and contraction of the wood and fabric components of the painting. Wood and fabric absorb moisture wich causes them to swell on humid days and conversely shrink on dry days. Paint, however, is not as resillient and can crack and flake off as a result. These dimensional changes can cause the canvas to become slack and sag during the winter months in some areas.
The proper display and storage of fine paintings can be achieved by monitoring the environment in various rooms in order to identify the best area for display or storage. Acceptable temperature and humidity levels for paintings are as follows.
Winter: Temperature 65-70 degrees F
Relative Humidity 40%-45%
Summer: Temperature 70-75 degrees F
Relative Humidity 45-55%
Inexpensive temperature and humidity snesors can be purchased from conservation suppliers. While precise control of temperature and humidity is not always practical in homes, simply keeping paintings away from heat sources such as furnace vents, fire places, warm lights or direct sunlight are easy ways to avoid damage.
Excessive humidity can be found in some basements, which can lead to mold growth and staining of the painting, so avoid this as a storage option.
Aside from the unsightly appearance of dirt on a painting, dirt also serves as a host for mold growth and the absorption of pollutants and moisture onto the surface of a painting.
Smoking, close proximitiy to candles or fireplaces can deposit nicotine and soot onto the surface of the painting.
Soft brushes can be used to remove surface dirt from paintings and frames. If surface dirt cannot be removed by dusting, cotton swabs that have been dampened with distilled water can be lightly rolled on the surface to remove dirt. If there is flaking paint, no attempt at cleaning should be made.
Insects that can cause damage to oil paintings include carpet beetles and powder post beetles.
Carpet beetles generally subsist on protein-based materials that may be included as a sizing material on canvas paintings. Insects are most often found at the back of the painting betweent the canvas and stretcher. Holes in the canvas, or the presence of worm-like insects or furry carcasses are an indication of carpet beetle problems.
Powder post beetles characteristically bore small holes into wooden materials. Frass, a substance that looks like saw dust, is also a good indication of an active infestatation.
If insect infestation evidence is found, the painting should be placed in a plastic bag and isolated until it can be examined by a professional convervator.
The greatest amount of damage to artifacts is caused by careless handling. Prior to moving a painting, be sure to remove all jewelry, belt buckles, etc. so that the painting is not accidentally torn or scratched while being moved. When moving a painting, always be sure to grasp the painting from both vertical sides. Do not hold a painting at the top of the frame or y its hanging wire. Avoid bumping canvas paintings, as even the slightest bump can cause future cracking of the paint surface.
Source: The Care and Preservation of Oil Paintings by Mary Fahey