Thinking of investing into some fine art?
From the moment an artist completes an oil painting---the painting begins to change color. The shift is gradual, taking decades, even centuries. But eventually some colors fade, others darken and many become more transparent over time.
Oil paint is made of pigment particles suspended in an oil binder. Certain colors are more susceptible to aging, depending on what was used to make the pigment.
For example, mineral-based pigments such as verdigris—a green color made from copper and common in oil paintings from the 15th Century—changes to a dark brown over time. This turns forests and flora darker, or even dreary.
Pigments produced from organic dyes, such as rose madder and indigo, are susceptible to fading when exposed to light. And the loss of color from a yellow gamboges glaze, based on plant resins, can make green foliage in Dutch flower paintings appear blue.
Environmental contaminants can also be damaging to colors. Hydrogen sulphide in the air converts white-colored lead-based paint to black-colored lead sulphide. And if that weren't enough to keep restoration experts busy, natural resin varnishes meant to protect paintings turn yellow with age. This makes an artist's white highlights in the paint underneath seem stained, and causes blues to appear green and reds to appear orange. Proper storage, out of direct sunlight, and in particular, with controlled temperature and humidity, can slow aging processes.
Preservation is important because shifts in color and opacity change the way we perceive paintings. The illusions of depth and three-dimensional form depend on subtle transitions in color and tone that are often obscured, and sometimes lost, as a painting ages.
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