Conservation Department

Preventive Conservation

Works on Paper

Reducing deterioration
Works on paper encompass a wide variety of media – watercolours, prints, drawings, maps, documents, screens and scrolls, to name a few. This range of media is found on many types of paper support. Works on paper will deteriorate at different rates, depending on when they were made and the materials and techniques that were used. However all processes of deterioration are affected by the environment – control of light, heat and humidity levels can significantly slow down the rate of deterioration. Museums and galleries have strictly monitored environments in order to minimise damage to collections.

Inherent instability
A high level of acidity is probably the single most damaging factor for paper. Paper can become acidic for a number of reasons. Prior to the late eighteenth century, paper was usually made from fibres such as linen and utilising processes that resulted in a chemically stable product. However, many papers made after this date are subject to the use of bleaches, loaders, fillers and acidic sizes. In the nineteenth century the inclusion of woodpulp became commonplace. These changes led to the production of paper that were of generally poorer quality. When paper deteriorates there are a number of clear visual signals that indicate problems – typically it may become discoloured, brittle and develop disfiguring brown spot stains, known as foxing. Foxing usually evolves as a result of metallic impurities and micro-organisms in the paper. Sometimes the inks and pigments applied to the paper are acidic, resulting in localised loss or fragmentation of inscriptions or images where the paper is attacked. Acidity can also migrate into a work on paper from poor quality mounting and framing materials. Some of these problems can be dealt with through professional framing and conservation treatment.

The environment

Light
All light causes irreversible damage to works on paper. Natural light and fluorescent light sources are rich in ultra-violet radiation, the most active and damaging part of the spectrum. Sustained exposure to light can cause paper to become brown and brittle; pigments and inks can fade rapidly. The combined effect of darkened paper and dulled image can alter the appearance of a work beyond recognition.

• Display works on paper in low light levels, well away from windows and strong light sources. The recommended museum level is 50 lux.
• Reduce light levels by drawing the curtains during the brightest part of the day. Prevent sunlight from falling directly on works. Install UV filters on fluorescent tubes. Never spotlight a work on paper.
• UV filters can be used on windows and glazing in frames.

Relative humidity and temperature
Excessive levels of heat and moisture in the air can be extremely damaging to works on paper. High humidity and temperature will accelerate the rate of acidic degradation of paper, in addition to encouraging mould growth. In an environment where the humidity and temperature fluctuate dramatically, a cycle of expansion and contraction can be generated in the work o art, causing the support to cockle and the pigments to flake and crack.

• Display and store works on paper in a cool, dry environment. The recommended museum levels are 20ºC and 50%RH.
• Try to avoid marked fluctuations in temperature and humidity – hang framed works on paper on inside walls, well away from direct sources of heat such as fires and radiators.
• External walls tend to be damper. A stopper placed behind a framed work, at each corner, will allow air circulation and reduce the risk of mould growth.
• Avoid hanging works on paper on walls in close proximity to kitchens and bathrooms.

Dust, insects and pollutants
Insects will thrive in an undisturbed, dusty environment. Paper, together with sizes, adhesives and binders provide an ideal food source for insects. Dust can be abrasive and can retain chemical contaminants, which will degrade works on paper. Airborne pollutants found in city atmospheres compound acidic degradation problems in paper and can engender colour changes and fading in pigments. Unsealed wooden furniture and fresh paint and varnish also emit pollutants.

• Keep works on paper in a clean, dust-free environment. Inspect stored material regularly for signs of insect activity or other damage. Isolate any suspect material from the rest of the collection.
• Restrict dust, insects and pollutants by using well-made storage boxes and frames that provide a good seal against the environment.
• Always use archival quality, acid-free framing and storage materials.

Handling
Paper is easily torn, creased and punctured. A great deal of damage has been caused to works on paper through rough handling and inappropriate repair.

• Always handling unframed works on paper carefully, preferably using clean cotton gloves. Support unmounted works on rigid board.
• Never repair tears or punctures with pressure-sensitive tape, animal glue or rubber cement. These quickly degrade, causing repairs to fail. Adhesive can migrate into the paper causing staining and embrittlement.
• Archival quality repair adhesives and tapes are available from conservation suppliers – these are useful for some simple tear repairs on archival material, but are not always appropriate for works on paper.

Storage
Works on paper should be stored in a clean, cool, dry environment, using archival quality materials. Storage systems depend on the media and whether the works are framed, mounted or loose.

• Store framed works, vertically and with the image the right way up. Separate frames with rigid cardboard and protect intricate mouldings with bubble-wrap.
• Mounted, unframed works should be stored horizontally in rigid, acid-free folders or archival boxes. Store similar sizes together or larger works on the bottom. Do not over fill boxes. Interleave works with acid-free tissue. Attach an inventory to the lid of the box or the front of the folder.

Mounting and framing
Poor quality mounting and framing materials become acidic. When works on paper are placed in close proximity to sub-standard materials, acidity will migrate into the paper engendering discolouration, staining and embrittlement. There may also be tonal changes and fading of certain pigments. Fixatives and varnishes are sometimes suggested as a means of sealing the surface of friable media such as pastel, chalk and charcoal drawings on paper. Unfortunately, fixatives cause irreversible texture and colour changes – delicate matte surfaces can become shiny and compacted and colours can take on a harsh, saturated appearance. Tonal balance can be further altered by the darkening effect of the varnishes and fixatives on the paper support. Both fixatives and varnishes will discolour on ageing.

• Mount works on paper using 4 ply, 100% rag board, buffered with an alkaline reserve. The mount should comprise a backboard, to which the work is hinged, together with a window to separate the surface of the work from the interior of the glazing. Archival quality tape or paper hinges should be used to secure the work to the backboard. Never attach a work to the underside of the window.
• The frame moulding should be sturdy enough to support the glazing, the mounted work and a backboard. Seal the backboard in the frame using brown-gummed tape or similar to restrict dust and insects.
• Never use fixatives or varnishes on your work on paper. The best protection for woks in friable media is to mount and frame them to conservation standards. Always use glass in the frame and a window mount to separate the delicate surface of the drawing from the glazing. Never roll a work with a friable surface.
• Never use acrylic glazing such as Perspex or Plexiglas when framing works with a friable surface. Acrylic glazing carries an electrostatic charge and will attract and disrupt loosely bound particles of media.

Never attempt to treat a damaged work of art on paper yourself. Consult a conservator, who will be happy to provide advice and information.