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Conservation of Works of Art on Paper: Prints, Drawings and Watercolours

By Catherine Rickman and Stephen Ball

Paper is still the material on which the majority of artists' images are produced. Works of art on paper appear in almost every public collection and cover a vast range of subject matter.

Paper was probably invented in China some time during the second century AD, but it was not until the twelfth century that papermaking reached Europe when the Moors introduced the process into Spain. By the middle of the fifteenth century the invention of printing had fuelled a huge new demand, and paper was in common use as a picture support across the whole of Europe.

Materials

The raw material of paper, whether it carries old master drawings or present-day prints, is cellulose obtained from vegetable fibres. The fibres are combined into a mat and bound with adhesive additives, and may be further treated to provide other desirable qualities such as whiteness. The strongest and most durable papers come from the long fibres of linen, cotton or hemp, often obtained from rags. However, although pure cellulose is extremely durable, the various additives can cause deterioration, usually through acid degradation of the fibres.

Rag-made papers long ago ceased to be used for everyday printing, which is now dominated by papers based on wood pulp, but they remain favourite supports for watercolours and other artworks. Wood-based papers vary widely in quality, from the wholly 'mechanical' varieties suitable for ephemeral applications to the chemically treated 'wood free' varieties designed for longer life. ('Wood free' wood-based paper may sound like a contradiction in terms, but is simply a paper free of untreated mechanical wood.) Some present-day papers may even have plastics added to the mix.

Paper is not chemically inert, is easily soiled or stained, and swells and contracts with the humidity of the environment. Wood-pulp produces more reactive, and thus shorter-lived, papers than rag, with the reactivity increasing with the mechanical wood content. However, the care and conservation requirements are similar for all types of paper.

There is no guarantee that a watercolour, print or other work has been rendered on the best available support. Knowledgeable artists may have chosen wisely, but it is likely that some works - important sketches in notebooks, for example, or prints from some periods - were not created with posterity in mind and may suffer from poor paper. Remember too that other paper materials, especially card or board, may be in contact with the work in the form of mounts or backings.

Media

The media that convey the artwork's image may be unstable too. Pigments can fade or darken, and often unequally because of their varied origins. Some drawing-inks bleed or corrode the paper, and some printing inks, especially soft blacks, are easily abraded. Other media are inherently fragile: pastels and charcoal are easily smudged, and thick paint such as oils and gouache can flake off.

Make sure that you have properly identified the media. If you are unsure whether a work is a print or a watercolour, for example, then contact a conservator for help. Note that a hand-coloured print is an example of a mixed-media work; the added watercolour may or may not be contemporary with the original print.

Damage

Exposure to light - especially ultraviolet light - harms both media and paper, but poor-quality mounting and framing damages more works of art on paper than any other agent. Prints, drawings and watercolours can be ruined through contact with unsuitable framing materials, just as they can by amateur restoration and the use of inappropriate techniques in handling, storage and display.

Atmospheric pollutants, such as acidic gases containing sulphur compounds and particulates, are implicated in the destruction of paper. They can change artists' colours too, for example by reacting with organic pigments or binders such as egg white. Biological agents, like insects and mould, affect paper, but they will only flourish as a result of poorly controlled environmental factors, such as high humidity and temperature. Temperature and humidity are interrelated, and must be monitored and controlled in harmony.

Signs of damage

Most owners of old books, watercolours, drawings or prints are familiar with the disfiguring brown spots called foxing. These stains are caused by the bacteria or mould that generally grow on acidic paper when the humidity is high.

It is not just the nature of the support itself that influences its condition. Even good paper will turn brown and brittle when card containing unpurified wood pulp is pressed against it. This is how so many framed works of art on paper are damaged; they are stained on the back and have a brown or orange line around the edge of the image where the acidic mount has 'burnt' the paper.

Yellow stains on paper, especially in regular patches, can be caused by glue or adhesive tapes used to fix the picture into a mount. Do not reach for the self-adhesive tape dispenser to repair tears - adhesive tapes are particularly damaging because the glue creeps into the paper and becomes impossible to remove.

Too much light is usually to blame where a watercolour painting exhibits a strange colour balance or an ink drawing has lost its detail. The original colouring can often be discovered when the mount is lifted and the protected edges of the picture are revealed.

A certain amount of cockling or undulation is usual in handmade paper, but if the work of art is badly distorted, bowing towards the glass in a frame and perhaps wrinkled or even torn at the corners, then it is probably stuck down around the edges. Paper moves naturally in response to changes in humidity, so it is better not to restrain it. Again, call in a conservator if a stuck-down mounting is causing damage to the work.

Storage and Display

The best way to keep most prints, drawings and watercolours is in a specially designed case called a Solander box. The works of art are first mounted in conservation-quality materials, or placed individually in acid-free paper folders, and protected from light and dirt by the box. Plastic sleeves are not suitable for the long-term storage of artworks on paper. Boxes, folders and portfolios must rest horizontally in drawers or on shelves.

When handling a work of art, touch the paper as little as possible and keep your fingers away from the image. This applies equally to present-day prints - the risk of damage is just as high because their immaculate paper is easily marked by skin moisture and oils, so keep them in a mount or acid-free paper folder. It makes sense to demand, as a matter of museum policy, that all persons handling works of art on paper wear cotton gloves.

Pastel and charcoal drawings need extra care because any pressure or abrasion may offset (smudge) the image. Consider keeping such fragile works permanently framed; but do not use modern spray-type fixatives or other materials to preserve them - instead, refer all preservation issues to a specialist conservator. Another danger for these media is the use of acrylic (such as Perspex) glazing when framing. Plastic glazing can carry a considerable static charge that will literally pull the medium off the paper.

You must specify acid-free mount board for all framing (suitable materials are also known as 'museum quality' or 'conservation quality'), and the framer should follow the guidelines for conservation framing published by the Institute of Paper Conservation.

Protect framed prints, drawings and watercolours from all sources of light. Ultraviolet filters (which need periodic checking and replacement) are desirable for both natural and artificial light sources. Of course, display is not possible without light, so try to control the light falling on works of art by using the minimum comfortable light levels for viewing, and visitor-operated time switches or curtains. Never expose a picture to the relentless glare of a spotlight. Take advice from a conservator on measuring and setting the light exposure of items on display.

Try not to hang works of art against the interior of the outside wall of a building; the comparatively low temperature can cause condensation and mould growth inside a frame. Conversely, a radiator or spotlight will dry the air out, and incidentally concentrate dirt by creating convection currents. When choosing a suitable storage area, avoid damp cellars and uninsulated attics. For all classes of object, it is wise to 'zone' your museum buildings based on the environmental characteristics of the various spaces, and place the collection accordingly.

Cleaning and Repair

When the damage is already done, there is little that the non-specialist can do to clean or repair works of art on paper. Traditional remedies such as bread crumbs to clean off dirt and commercially
produced tapes to repair tears may do more harm than good, unless the alternative to temporary taping is further fragmentation of the separated parts and a serious loss of material. In this latter case, hand the damaged work to a conservator as soon as possible.

If prints and drawings get really wet, for example from a burst pipe, it is better to lay them out separately on blotting paper to dry using a good cool air circulation, rather than use an artificial heat source. In the case of a serious flood or a fire, get help from a conservator as soon as possible. But you must also try to anticipate sources of damage - for example, you would not display watercolours under a ceiling that conceals a water tank and its associated plumbing. Your museum should have a documented and rehearsed disaster policy.

Contact a paper conservator through the Conservation Register and they will advise on the most appropriate treatment for your picture. With professional treatment, the condition of the paper and image can at least be stabilised so that their deterioration won't progress. Most damage can be corrected by a skilled conservator, but remember that faded colours cannot be restored to their original brightness and severe paper staining may only be reduced rather than removed.

Sources of Information and Advice

Further reading/useful contacts:

Anne F. Clapp, Curatorial Care of Works of Art on Paper, 1987.
ISBN 0-941130-31-2

Guidelines for Conservation Framing of Works of Art on Paper is a leaflet for framers and collectors, obtainable from:

Institute of Paper Conservation
Bridge House, Waterside
Upton upon Severn WR8 0HG
Ph: 01684 591150
Fax: 01684 592380
Email: information@ipc.org.uk
Website: http://www.ipc.org.uk

Hermione Sandwith and Sheila Stainton, The National Trust Manual of Housekeeping, Penguin, in association with the National Trust, revised 1993. ISBN 0-14-0123344-X

For more information about private conservation work please contact:

Conservation Register
Tel: 020 7721 8246

Conservation Register (Scotland)
Tel: 0131 668 8668

Copies of this fact sheet can be provided in alternative formats. Please contact Viola Lewis, Information Officer at MLA for further information.

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