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After you have owned a painting for a while, you may begin to notice that the image longer appears as clear or sharp as you remember. If the painting has been properly handled and displayed then the changes are probably due to the natural aging of the painting. Described below are aspects of the natural aging process of paintings.
Dirt, Grime, Soot and Smoke Collect
Paintings do accumulate dust over time and dust alone can obscure the image. However, grime from other sources such as soot and tobacco tars will also accumulate on a painting surface. Although most grime can be carefully removed, soot and smoke damage may permanently alter the tone of the painting, especially if the support is unprimed or the painting unvarnished.
The Varnish Layer Ages
Traditional oil paintings usually have a final coat of varnish over the paint layers to provide the saturation of colors and to protect the painting from dust and atmospheric pollution. Traditional varnishes are natural resins which, when applied in a thin coat on a surface, dries to a hard, glossy, and transparent film. Natural resins darken with time and the image on a painting may become difficult to see and the tonal balance altered.
The Materials of the Painting Age
From the moment a painting is made, it begins to age. Depending upon the quality, combination and nature of the materials which have gone into its construction as well as its environment, a painting may age well or not. A new painting in good condition will begin to deteriorate as a result of time alone. Its materials go through a drying process which sets up internal stresses in the structure. This may continue for a period of years, decades, or centuries. As the paint films dry they shrink and the films rupture or pull apart in cracks. If the painting has been well constructed and the artist has used sound techniques, the painting does not suffer in appearance. Small cracks may catch and hold dirt, but the removal of the dirt by a superficial cleaning in many cases eliminates the disfiguring effect.
If the paint film is thick and contains too much oil, the surface may wrinkle. An improperly prepared ground layer can also cause disciguring cracks on the surface. As the painting continues to age, both the paint film and priming lose flexibility and become brittle. Expansion and contraction of the fabric support, due to absorption and release of moisture from the air, adds further strain which leads to crack formation.
Some Pigments Change
Some pigments are naturally sensitive to ultraviolet light, acids or bases. Exposure of these sensitive pigments to any of these conditions will cause them to fade. Sunlight naturally contains ultraviolet light, so exposure of a painting with sensitive pigments to direct sunlight can cause those sensitive pigments to fade. Also, treatment of a painting with either acidic or basic cleaning solutions can cause some sensitive pigments to discolor.
Physical Damage Happens
Cracks can also be caused by mechanical means, such as pressure, large or small, on either the front or back of the painting. Almost any marks placed on the revers of a canvas will, in the course of time, affect the surface. Writing on the back can cause the paint to flake off ont the front of the canvas, wetting of the canvas from the application of labels can cause cracks, and any sharp blow will inevitably leave its mark even if it does not rupture the canvas.
What To Do?
Beyond conscientious care and careful handling of your paintings, there is little you can do to prevent natural aging. Paintings conservators can aid in preserving you paintings for the greatest time. Paintings conservators are professionally trained individuals with years of experience. You should solicit the advice of services of a conservator any time that you have questions of concerns regarding a painting. They can help you with the general upkeep of your paintings (dust and grime removal) as well as handling any unfortunate mishaps (paintings that fall from their hooks, fire, flood, insect damage, etc.).
Conservators are committed to the preservation of the original artwork. They will do everything in their power to regain and preserve the artist's original intent. They will not alter or modify a painting to indulge an individual's personal taste. The goal of a paintings conservator is the preservation of cultural heritage.