Caring for works of art on paper
Paper is a relatively fragile material, so it is not surprising that works of art on paper (prints, drawings, watercolours, and so on) can be easily damaged. Factors in the environment, including damp, and light, as well as handling, and the materials used for mounts and storage folders can all be culprits in causing serious damage. However, if a few fairly simple measures are followed damage can be avoided and works on paper can be both enjoyed, and kept in excellent condition.
Damp and light are the two environmental factors that, in my experience, contribute most harm to paper. A damp environment (above 65% relative humidity) can promote mould growth on paper, with black, white, and coloured spores and stains. Damp may also give rise to the appearance of foxing (small brown spots) which can be very disfiguring. Damp can cause paper to expand, and so create undulations or ripples across the sheet. Perhaps less widely known is that a raised humidity increases the rate of transfer of acids from poor quality mount card, or frame backings, that are in direct contact with paper.
To prevent these problems works on paper should always be kept in a dry environment: around 50% humidity is recommended. You should avoid hanging framed works on walls that may be damp. If this is unavoidable small spacers (for example 5mm slices of a bottle cork) can be adhered to each corner on the back of the frame to create space for air to circulate between the frame and the wall. This inexpensive practical tip could prevent some very disfiguring damage.
Light can damage both the paper support and the media of the image. Good quality papers, usually those with a high cotton fibre content, will fare better on exposure to light than those that are made of cheaper fibres, such as wood pulp. All papers degrade in light, but wood pulp or mixed fibre papers degrade more rapidly and can turn from white or cream to yellow and brown. The degree of damage will vary according to the brightness of the light, and the duration of the exposure. Natural light has an ultraviolet component, and it is these wavelengths, invisible to the naked eye, that are most damaging.
Not all types of media will be affected by light. Many printing inks will be relatively stable in light. But an ink drawing or a watercolour with lightly applied washes could fade badly. When a window mount is removed it is always interesting to compare the area that has been hidden from light with that which has been exposed, to check for faded media, and a change in paper tone. You may be surprised by what you find!
To prevent damage from light I recommend that works on paper should be displayed on walls that do not receive direct or strong light. Long periods of display, especially for the most vulnerable works (ink drawings, watercolours, and works on poorer quality papers) should be avoided. The ultraviolet content of light can be cut out both by high quality frame glazing, and by screening on windows.
The quality of the board that is used for the window and back mounts when a work on paper is framed is crucial to the preservation of the work. If a work is mounted with poor quality board the acidity from that board will transfer to the paper of the art work and cause discolouration of the paper. Even worse than poor quality board is the lack of board at all: if a work has been given a window mount, but no card covering the back, it is in direct contact with the highly acidic wood backing of the frame, and after a period of years the consequences are visible in strong discolouration of the paper. Of course if adhesive tapes such as Sellotape or Masking tape are used to attach the artwork to the mount bad staining will result. A great deal of my work as a paper conservator has been created by framers!
A good quality mount board is made from 100% rag fibres, and has a buffering agent to bring the alkalinity of the board to about pH8. It is marketed as ‘Museum quality’ board, and is usually a cream or off- white tone. You can recognise it by looking at the cut bevel edge of the window. If the quality of the card is the same all the way through, with no laminated surface papers, it is likely that the card is of a good quality. The Fine Art Trade Guild run an accreditation scheme for framers, and a list of framers who have achieved this qualification, and can carry out mounting and framing to conservation standards, can be found at www.fineart.co.uk.
Physical protection for works on paper is crucial to preserving them in a good condition. If a work is mounted in good quality board, and framed, it will be physically very well protected. A work that is not framed is vulnerable to damage from handling, as paper can easily become dog-eared, soiled or torn from handling. It will also be subjected to damage from dust and dirt, and other air pollution from the atmosphere. It is therefore essential to keep unframed works covered and protected. Simple acid free card folders are very useful for storing and transporting works. Do make sure that the folder is larger than the art work: if one end is sticking out is almost sure to get creased and soiled.
For an outline of the conservation treatment of some examples of works of art on paper please visit our ‘Case Studies’ page.