Paintings can be adversely affected by sunlight, heat and air pollution. With one or two obvious exceptions, such as not siting pictures above an open coal or log fire, there is not much that can be done about the last of these. But care can be taken with the first two.
Protection against sunlight. When hanging pictures, make sure they are not going to be hit by direct sunlight. Watercolors and pastels are particularly vulnerable to fading; oils, to a lesser extent. Once faded, the color cannot be restored. A good place to hang pictures is on a wall between two windows, as long as shafts of sunlight cannot hit the painting through gaps at the sides of curtains or blinds.
If a room is very sunny, hang only one picture in it and move pictures either round a room or from room to room so that they get equal exposure.
Draw the curtains when you go out or when you are not using the room, to minimize exposure to sunlight. Somebody once said that this makes a room ‘gloomy’, but what does it matter if you are not there?
If you have several paintings of actual or sentimental value, you might put them all in the darkest part of the house, which is usually the stairwell, and turn it into a mini gallery.
Delicate, light-sensitive pictures are better glazed. Choose a low-reflecting glass with a UV filter (sometimes called ‘museum glass’). This is more expensive than ordinary glass but will protect the painting from sunlight very effectively. Some of it is virtually unbreakable, too.
Protection against heat. Central heating can cause damage to paintings – not just because of the heat but because of the dry atmosphere in creates. Problems arise when the heating is turned on once or twice a day – as most of us tend to do – because it causes fluctuations in temperature. When a room is warm, the humidity falls; as the temperature drops, the humidity rises. Pictures are particularly prone to damage from these fluctuations in heat and humidity because their constituent parts are affected by heat and moisture at different rates. This applies even to the canvas itself and the paints upon it. Too many changes in temperature can cause the paint to crack and even flake off the canvas. In some cases, wooden frames can expand and contract and break the glass in a picture.
Do not place pictures directly above a radiator or any other source of heat. And do not hang them on walls carrying internal hot pipes. Do not site picture lights too close to the top of a painting. The danger comes not so much from the light as from the heat of the light, which can scorch the painting.
Conversely, cold and damp do not do pictures much good either. In these conditions, pictures are likely to develop mould (the light brown spots known as ‘foxing’).
If you want to use a picture light, make sure it is placed far enough away so as not to cause damage, but near enough to give a reasonable pool of light. Make sure, too, that the covers on the lights are long enough to ensure the painting does not get too hot.
Protection against air pollution. Fewer of us have open fires these days, but if you do, have pictures glazed to stop soot damaging the surface. The same applies if there are heavy smokers in the house. It is far easier to clean the glass than to clean the surface of a painting. Do not hang pictures directly above a fireplace that is used frequently.