Pictures should be hung securely using nylon cord for preference. There are various strengths of cord so check with your dealer for the most suitable. Brass or copper picture wire can also be used but it can corrode over time. String is not normally strong enough and it can also stretch and be prone to rotting. Eyehooks should be screwed into the frame only and not the stretcher or backboard. For smaller works,'D hooks' can be attached to the backboard provided a barrier board is also used to prevent contact with the work. Both the strength of the hook and its fixing into the wall must be commensurate with the weight of the picture. For very hard walls special hooks are available or alternatively the wall may need drilling. It is usually advisable to use two hooks, not only for additional safety but also to prevent the picture 'swinging'. Very heavy paintings may also need to be supported at their base by brackets fixed to the wall, or by two short lengths of chain hung vertically from secure fixings and hooked onto brass plate hooks screwed into the frame.
Avoid hanging pictures over a fire or radiator, unless there is a mantelpiece or radiator shelf, as dirt and smoke in the warm airstream will be carried up and could mark the picture. Watercolours will fade if hung in strong light, especially sunlight, and some types of paper may discolour; it is best to hang them on a wall which receives indirect light. Consider covering vulnerable works on paper with a cloth when away on holiday, especially in the summer, or draw the curtains in the room. Alternatively roller sun-blinds cut out the rays of the sun without darkening the room. Because of their sensitivity to light, valuable works on paper should never be photocopied. Oil paint is less likely to fade but will sometimes dry and crack in high temperatures caused by central heating, fires, direct sunlight or even picture lights. Panels too may warp or crack as a result of heat or extremes of temperature. Wide variations in temperature and humidity are not good for any works of art. Do not hang pictures on damp walls.To help air circulate and avoid the build-up of any damp, especially if hung on an outside wall, allow a picture to lean away from the wall at the top and also glue a thin sliver of cork from a wine bottle or a corn pad on to the bottom corners of the back of the frame. While damp can leave brown tidemarks or cause paper to ripple when it dries out, very dry conditions, often caused by central heating, can make paper dehydrate and become brittle. Humidifiers and dehumidifiers can solve these problems.
Framing & Mounting
Traditionally, oil paintings are framed without glass as they already have the protection of their coat of varnish. However works on paper -watercolours, drawings and prints -must be glazed to protect them from surface damage and dirt. While perspex sheeting can be used and is lighter and less fragile than glass, it scratches easily and attracts dust. For valuable works on paper, consider glazing with one of the modern UV filter glasses which are expensive but can filter out up to 95% of harmful UV rays.
It is important for works on paper to be set behind a card 'window' mount as this separates the glass from the artwork, preventing any rubbing and providing some circulation of air to deter mould. Both the bevel top window mount and the undermount must be acid-free as acidic paper will eventually discolour and in damp conditions it can develop mould or brown spots known as 'foxing'. You can check whether an existing card mount is acidic by looking to see if there is a brown stain around the inner edge of the 'window': if there is then the mount should be replaced. In order to allow paper to expand and contract, it should not be taped directly to the undermount but attached to it with T-shaped paper hinges fixed to the back or held by conservation-quality paper corners. With valuable works on paper, it is worth considering changing the mount and backing every ten years or so.
When fitting the work into a frame, the whole should be backed with modern double-sided smooth hardboard. Never use a wooden backboard as it is acidic, nor grey pulp board. Pin the backing into the frame and seal the edges with gummed paper tape to help keep our dust and insects. It is not advisable to have works 'drylaid' onto an undermount.
It is important to store oil painting and works on paper in clean, dry conditions, preferably somewhere dark and where the temperature is cool and fairly constant. Paintings should be placed upright on blocks to keep them off the floor with acid-free board between each one. The largest and heaviest should be at the back of the stack and picture hooks should be removed to prevent them damaging the next frame or canvas. Cover the stack with a clean dustsheet but do not use plastic as this can cause mould. Unframed works on paper, such as maps or prints, are best kept flat in acid-free boxes or folders with acid-free tissue between each work.
Cleaning and Conservation
Apart from dusting frames and the glass protecting works on paper, picture cleaning should only be done by a skilled professional. Never clean gilded frames with a damp cloth or sponge as this will eventually remove the gold leaf. Flaking oil paint, dirty varnish and a whitish bloom on the surface of an oil painting caused by damp can all be treated without too much difficulty by a professional restorer. Stains and foxing on works on paper can also usually be dealt with by a paper conservator. Inspect your pictures regularly as any signs of damage or staining should be dealt with as soon as possible to prevent further deterioration which will make the problem more difficult and expensive to deal with.