Conservators support the Tate's core purpose to care for the National Collection of British, Modern and Contemporary art, and artworks on loan to Tate. In addition to restoring artworks, they examine and document the artist's materials and techniques used to make each work. This may involve detective work to discover old techniques and materials no longer used today. Or it may necessitate research into new materials to assess their possible long term behaviour. Conservators and conservation scientists predict long term change in artworks by recording their condition and logging any subtle shifts in their structure or appearance over time. They assess ways of slowing down the aging process. This includes making recommendations for best practice in the lighting and environmental conditions of display galleries, storage and transportation.
Conservators also track the condition of artworks while on display at Tate and when on loan to other venues. They encourage best practice by researching and specifying low risk methods to handle, pack, store and transport artworks. They search for new ways of preserving art while making it as accessible as possible, and increasing knowledge and understanding of the material history and concepts inherent in an artwork.
For more information on the care of paintings see the ICON (Institute for Conservation) website at http://www.icon.org.uk/.
To store a painting, consider protection from dust, mould, insects and from abrasion or impact. Ideal conditions are those that are stable - neither too dry nor too damp. 50% relative humidity, and 20°C are standard environmental conditions for storage. Exclude light to reduce fading and discolouration. Protect from dust with a suitable covering; this could be tissue paper or polythene. For modern paintings and unframed works, consider providing a carrying frame, or L-section wooden frame, that projects far enough beyond the front of the painting to allow the frame to be wrapped in polythene without touching the paint surface (see packing methods).
Painting Conservators can answer questions or direct you to other sources of advice. See the 'Contact us' section of the website.
Tate's Collection is available for display at all of its four sites, therefore artworks must be
moveable. For paintings, the display frame is the most vulnerable part of the work. It is the
means by which the work is handled and may be exposed to the occasional unintended contact with
objects and surfaces. A simple L-section wooden frame, or 'carrying frame' is often supplied to fit
the painting into for extra protection:
Transit Frame
Specification (PDF)
The L-section projects out in front of the painting and its frame.
There is a gap on all four sides so the work can be secured. A carrying frame is especially useful
for works without display frames. It is a simple measure, but a very effective one for reducing
wear and tear. It can also be wrapped in polyethylene sheeting which, when overlapped and taped,
provides a stable atmosphere around the painting for storage. The only risk comes if the painting
itself is in a damp environment. The high moisture content in the framed painting will make the
trapped air humid and in time mould could form. Tate stores its paintings in air conditioned
buildings so this is not a concern.
For national transport Tate uses air-ride suspension temperature-controlled vehicles. Because the temperature in these vehicles is kept similar to that in the museum, the painting in its wrapped carrying frame is considered adequately protected. Blankets are often used to absorb shocks when a painting is put down. Straps are then used to hold the work against the inside of the lorry and to secure any other items in the vehicle.
For international loans requiring transit through an airport, the rigours of cargo handling make the
provision of a packing case with cushioning and a resilient external shell essential. Packing cases
are made by outside firms to Tate specifications. A typical set of packing specifications is provided
as an example here:
Specification for a Single Painting (PDF)
Very large paintings may have to be taken off their stretcher and rolled for transportation, but this should always be avoided where possible since removing and re-applying the attachments damages the tacking edge of the canvas. Furthermore, rolling may crack the paint. One absolute rule if rolling is necessary is that the paint surface must be face out or the paint will be creased and compressed, with ultimate adverse effects. A roller with as wide a diameter as possible should be used, with a minimum diameter of 1foot (31cm). If the painting is thickly and recently painted, it is highly likely that it is still wet. This obviously has to be carefully checked for. An interlayer of Glassine paper is a useful safeguard generally. Care should be taken to keep the roll off the ground by putting strips of foam or similar padding around each end, otherwise the weight will cause distortion and possibly cracking. Wrap the rolled up painting with polyethylene sheeting and seal. The painting on its roll should not be stored for long periods; problems may be developing.
It is not unusual for a painting to exhibit cracks. These occur when the stress applied to paint is greater than the force holding the paint film intact. Cracks are caused by stresses inherent within the painting or by external forces. An example of the latter would be if a painting is struck by an object, such as a swinging handbag or rucksack. This sudden force applied to the surface might cause the paint film to deform and crack quickly. Other cracks develop slowly over time, as a result of minute changes due to varying temperature and relative humidity levels. The different materials that make up a painting: the support, size, ground, paint, other media and resin layers all absorb and desorb moisture at different rates. Minute difference in expansion of materials can cause stress fractures that develop and grow more apparent over time.
Inherent stresses within the painting may be caused by the nature of the paint itself. Paint that is brittle is obviously more prone to cracking than paint that is flexible. Paint tends to become more brittle over time so most oil paintings over eighty years old exhibit cracks. There are many factors which influence the brittleness of paint: the type of media, the amount of pigment, whether the paint is thinned on application and how it is applied to the support. Ductile or alligator cracks occur as the paint dries, if the media shrinks and retracts. These distinctive cracks have soft edges and open networks, exposing underlying paint or ground layers.
The best way to reduce the chances of cracks forming is to control the moisture in the air, aiming to keep it stable and at a moderate level, ideally 55%RH. Where possible, extremely stable conditions can be achieved when the painting is sealed by surrounding it with moisture barriers; moisture impermeable backboards and having glazing fitted achieve this. When the painting is sympathetically lit, so that bright lights or windows are not reflected in its surface, low reflecting glass can be almost invisible.
Mary Bustin, Paintings Conservator and Tim Green, Paintings Conservator
February 2007
