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Articles and whitepapers on conservation and restoration.

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Taking care of tortoise shell artworks
Taking care of oil paintings
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LA Times Story

Care of Paintings – Oil on Canvas

By Rafail Golberg and Alexander Golberg.
June 26, 2009.

This article is for information purposes only, and is not intended as restoration advice. We recommend consulting with a professional restorer regarding your specific paintings and your particular display and/or storage conditions.

There are a number of different types of painted media and they are generally described by type of paint used and the surface on which is painted. For example: Oil on Canvas or Watercolor on Paper. Paintings can be as vast of the Ceiling of the Sistine Chapel or as tiny as a grain of rice. The diverse possible combinations limit ability to generalize, this article will focus on one of the most common: oil on canvas, unless expressly noted.

Hazards to Paintings

A variety of the environmental variables can cause problems for paintings.


One of the most important variables affecting the well-being of the painting is humidity level. Extremely high, as well as extremely low humidity levels can wreak havoc on paintings. Air saturated with moisture often leads to insidious mold growth or cause the paint layer to break and then pop-off. Excessively dry air can cause paintings to warp and crack.

Most humidity related problems can be avoided by maintaining a constant level of appropriate humidity between 40% and 60%.

Airborne particles

Candles, fires, and smoke (including tobacco) can cause acidic oily layers on a painting’s surface. Such layers can cause discoloration, and lead to paint layer loss. As a protection against these particles, a layer of varnish is applied to paintings to protect the paint layer. Varnish has a useful life of around 50 years, at which point, visible signs of airborne particles may appear on the varnish, which must be replaced as needed.

Exposure to airborne particles shortens the lifespan of the varnish layer. This protective layer should be replaced as it weakens, in order to offer protection to the paint layer. Additionally, a painting’s exposure to smoke from candles, cigarettes, or other burning or smoldering items should be avoided Lastly, air filtration systems can offer additional protection by removing most of particles from the air.

Light and Heat

Sunlight and working fireplaces (especially when a painting is hung above them) can cause flaking and cracking of the paint layer. Sunlight, via invisible ultraviolet radiation, can cause varnishes to yellow and pigments to fade.

These damages can be prevented with the installation of heat reducing UV block window coating. Also avoid turning off and on the air conditioning as artworks can be exposed to ruinous spot heating; it is best to maintain consistent air temperature level.

Canvas Issues

Paintings on canvas can exhibit problems with textile support. As part of the aging process, the canvas looses its firmness and elasticity. The most common damages to the textile support are as follows:

  • 1. Oxidization due to long-term absorption of atmospheric oxygen,
  • 2. Atmospheric acids attack the canvas,
  • 3. Damage causing mechanical stresses, including man-made tears,
  • 4. Mildew and bacteria.

These damages can slowly occur over time, often taking centuries before posing any serious problem. To prolong the health of original canvas, the painting should be in climate controlled atmosphere, as described above. If any signs to the canvas are noticed in the back of the painting, advice of a professional conservator should be sought.

Display and Storage

Most of the previously described damages can be avoided with proper display and storage conditions.

When a painting is not on display, proper storage is imperative. Always store paintings in a climate controlled environment and never place paintings in bubble wrap or brown paper. It is also advisable to interleaf the paintings with strong cardboard on a foam core board.

Routine cleaning, using a soft sable brush or lint-free cloth, should be attempted for removal of dust particles lightly attached to the paint layer but only if there are no loose paint layer chips.

Varnishes act as a protective layer over the paint layer; however, they also absorb airborne particles, causing them to darken over time. Cleaning of varnish by a professional is recommended approximately every fifty years, depending on the environment in which the painting has been stored. This treatment not only restores the vibrancy of colors, but is an important conservation procedure vital for longevity of the paint layer. Darkening of the paint layer is a sign of a need for professional cleaning and can only be properly and safely addressed by a professional restorer.

Oil paintings are subject to yellowing caused by dampness in the air, exposure to light and simply due to time. One of the signs that a painting needs attention, is craquelure: cracks formed because of oxidation, drying and aging.

Following the general guidelines will ensure the longevity of the painting without a need for frequent conservation work. These guidelines are as follows:

  • 1. Carefully hanging the paintings in a climate controlled environment,
  • 2. Avoiding direct sunlight and sources of smoke,
  • 3. Very careful dusting.
If damage does occur, it is usually best to address it right away; postponing treatment can lead to further deterioration.

Due to the delicate nature of paintings, restoration attempts should only be made by a professional restorer. Golberg Restoration Co offers a variety of restoration services for paintings. Please visit www.restorationworld.com/paintings.htm for more information.

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