Paintings are usually brought to conservators or restorers only after problems in their structure or state of preservation have become obvious. Aesthetic considerations are also a common reason for consultation. Tears, water damage, heat blisters and smoke damage from a fire are clearly the result of accidents. Other damage, such as flaking, cupping, and planar distortions, may occur with time. Similarly, both varnish and pigments used for retouching, like the colors of the painting itself will discolor and change over the years. If there is a smoker in the house there can be severe discoloration! The term paintings in this context refer to works on canvas, wood panels and academy board with media including oil, acrylic, egg tempera, etc.
Tears and flaking are the two most commonly encountered problems. In both types of problems, it is advisable to call an art conservator. If flakes of paint appear loose, a painting should be removed from the wall and stored flat. It is also important that areas of flaking paint not be touched. When packed for travel to the conservatory, the painting should remain in its frame so that a rigid cover such as a piece of fome-cor or cardboard can be supported by the frame to avoid disturbing the paint.
Flaking paint may indicate one of several different conditions. On occasion, areas of flaking paint have not fully detached but have lifted away from the canvas, ground or lower paint area. This condition is referred to as cleavage. Flaking usually reflects a breakdown in adhesion between the paint layer and the support. The problem may be inherent in the artist's choice of materials or may result from the deterioration of the glue size in the ground. These conditions are aggravated by seasonal changes in temperature and humidity. The canvas or wood expands under humid conditions and contracts under dry conditions. As a paint film age, it loses its elasticity and becomes even more susceptible to flaking, cracking and cupping. In treating flaking paint, a conservator will infuse adhesive into the flaking area and apply weight during the drying period.
Tears are another major cause of the alarm. A conservator should be called immediately and the tear should be left untouched. Distortions in the canvas start to set in almost immediately and the edges become progressively more difficult to repair. Immediate treatment, even if limited is advisable. If emergency mends must be applied to the back of the painting, any pressure-sensitive tape, such as Scotch or masking must be avoided! If the painting has incurred a sizable tear a lining may be required. A lining is also required when a canvas grows too weak to support itself. If a painting has one small tear a lining should not be necessary but in an area with extreme temperature changes, a patch may start to bulge with time and a lining would be advisable.
Bulges can sometimes be eliminated by keying out the stretchers. A painting should always remain taut but it is very important that the painting not be keyed out excessively. A canvas that is too tightly stretched out on a humid day could rip apart when the humidity decreases. Old paintings on wooden frames with no keys or frames of other materials are often replaced with stretchers that can be keyed out.
Mold is usually caused by excessive moisture either in the atmosphere or from flooding. It is most commonly found on the back of the painting, where the mold or fungi feed on the binding medium in the canvas or paste in the lining. A painting with mold should be removed immediately from its damp environment. The painting should be placed in a warm, dry environment or in sunlight to prevent further growth of mold and the conservator called immediately. The painting should be placed in the sunlight, with the back towards the light, for only a short period of time and not at all in the extreme desert heat.
Beetle larvae, termites and silverfish can attack wooden panels and stretchers. I have seen them eat their way through the canvas to eat the sizing, leaving the painting in pieces. If insect damage is found, the piece must be immediately isolated an a conservator consulted about fumigating the piece. Paintings should also be protected from roaches and flies which deposit small acid specks that are nearly impossible to remove from the painted surface and can corrode both the varnish and paint.