Oil paintings can be damaged by exposure to extreme heat and humidity. In fact, a painting will lose its vibrant colors in as little as five hours in direct sunlight. This is worse for works on canvas, which are prone to warping and splitting. While special frames are available to prevent these problems, no protection is guaranteed. Excessive heat will also cause smoke to build up on the painting's surface, obstructing the color of the paint.
While the sun is an excellent source of natural light, the sun's ultraviolet rays can cause fading. It's also recommended that you protect your oil paintings from direct sunlight and fireplaces. While direct sunlight doesn't fade the colours of an oil painting, prolonged exposure to heat can weaken the support and lead to cracks. This damage is often irreversible and cannot be reversed once it's done.
Hot or dry temperatures can also damage oil paintings. High temperatures will cause the support to expand and the layers of paint to begin to crack. Relative humidity should be kept at about 55 percent to avoid the risk of mold growth, which can attract bugs and rot the canvas. A warm room will also cause the varnish to bloom. This can make your painting look dingy and unattractive. By keeping your paintings out of the sun, you can protect them from these effects.
