Conserving Works of Art on Paper
by Joelle Steele
If you are an artist or you collect art, you’re probably aware of the damage that can occur if your drawings, prints, and watercolors are exposed to extremes in temperature and humidity, or if they are stored improperly and come in contact with pests or fungus. You can learn to conserve and store works of art on paper so that they are less likely to deteriorate and lose their appearance as well as their value.
Paper Content
Paper has been around for centuries. The best and longest-lived papers are those made from long linen or cotton fibers. These were originally made from rags, and so that paper is still called rag, and rag is the paper most desirable for creating original works on paper such as watercolors or pastels. But most papers are made of highly durable cellulose obtained from plant fibers and bound together with chemical adhesives, as well as whiteners or dyes. It is the chemicals used in making cellulose-based papers that cause the paper to be acid-reactive and to break down over time, thus shortening the life of the paper. This is particularly true of older works and those made at any time on lesser quality papers. Today, there are some cellulose-based papers that are designed to have a longer and healthier life, and they are made of “wood-free” materials (meaning they do not contain untreated wood fibers) and may even contain plastics. But even if an artist uses a high-quality rag paper, it is no guarantee that it will stand the test of time, because the very nature of paper makes it highly reactive to its environment. And how a work of art on paper is handled, stored, and displayed over a period of time can have a great impact on its longevity and its value.
Types of Damage to Works on Paper
Most people have seen the damage that can occur to paper. Recognizing the cause of the damage is important in understanding how to prevent it and how to combat it should it occur.
Foxing. These familiar brown spots on paper are the result of mold that thrives in cool environments under high humidity. It can also happen when a water media piece of art work is framed before it is fully dry. Even a small amount of dampness under glass can invite the growth of mildews and molds. Any kind of paper can become subject to this kind of damage, and the only way to prevent it is to follow the proper storage and display methods explained later in this article.
Stains. These come in many varieties, ranging from water stains to glue remnants. To prevent them, don’t store or display art in any location where there is a danger from roof or wall leaks, or where water could be splashed on it. Do not use self-adhesive tape or any kind of glue on a piece of art — it can be absorbed into the paper and cannot be removed. Some of these stains can also occur during the creation of the art itself, such as when an artist creates a collage using a glue or paste that is not archival and is therefore prone to deterioration.
Fading and Discoloration. Any paper can fade and discolor when it is exposed to light or the acids in wood. One of the most common forms this takes is that of a piece of art that has been displayed under a mat that is not acid-free, resulting in a discolored area on the part of the art that was under the mat and a dark rim or line around the mat’s opening (“mount burn”) where the wood acids burned the paper. Exposure of the paper to the wood in a frame or in a storage cabinet can result in the same problem. The pigments in a work on paper can also fade, sometimes to such a degree that the image is only barely visible.
Buckling. This is when the paper is distorted in such a way that it appears to be bubbling upwards towards the glass in a frame, or it will not lie flat in some way. Paper moves ever so slightly, expanding and contracting as it responds to changes in humidity, and in doing so, it can buckle in this way, especially if the attachment to the mat was done poorly. In the case of water media used on paper, buckling can also occur during the artistic process, and sometimes the only way to fix the problem is to very carefully flatten the paper and then reframe the art. To prevent most buckling, follow the proper storage and display methods explained later in this article.
Brittleness and Browning. When paper is exposed to high temperatures, it speeds up the acid reactions in the paper, which results in the paper becoming stiff and brittle, usually with “browning,” a darkening of the paper. Brittle paper is extremely prone to cracking and tearing, sometimes to the extent that the art work falls apart in your hands and cannot be saved or restored.
Insects. There are several pests that can easily destroy a work on paper. Among them are the following: Woodworms (Anobium punctatum) can literally bore through piles of paper or layers of paper and cardboard. Silverfish (Ctenolepisma longicaudata or Lepisma saccharina) eat paper and glues that contain starches, cellulose, linen, cotton, and silk. They live in dark, cool, and humid environments. Carpet beetle larvae (Attagenus unicolor or Anthrenus verbasci) are also destroyers of paper. They only do damage at the larval stage and prefer the rag and linen papers, but will eat what is available. They prefer to live in dirty carpets and upholstered furniture, and that is usually how they find their way to your works on paper.
Book lice. These pests (Trogium pulsatorium or Liposcelis divinatorius) like old paper in particular, especially if it has any old starchy vegetable-based glues in or on it. And termites and ants can migrate from the walls of an already infested building directly to any paper they find in it.
Media. Inks and paints and other media can be unstable or inconsistent in their own chemical composition. They can darken, fade, or in other ways discolor due to exposure to light or changes in humidity. This means that as the media rests on the paper or breaks down on the paper, it can also interact chemically with the paper and damage it or weaken it further. Artists, student artists in particular, are not always mindful of this fact when they select the type and brand of media and paper to use when they create their early works, so if there is media damage, it is often best left to a professional to restore the art work.
Manmade. Atmospheric pollutants contain acidic gases, such as sulfur, which can contribute to the destruction of paper and can additionally alter any organic pigments used when they chemically react with them. In addition, manmade damage can consist of such things as holes in the corners and sometimes other areas that were made by staples and tacks; pressure-sensitive, cellophane, and other adhesive tapes adhered to the paper; creases from folding; abrasions and tears from careless handling; dust and dirt; and writing or other marks made by someone other than the artist. Careful handling eliminates most of these problems, but if they occurred before you acquired the art work, you may have to just make the best of it and hide what damage you can under matting and have any visible tears or other damage addressed by a professional.
Preventing Damage
In general, it is best to not try to restore works of art on paper unless you are a professional. There is so much misinformation about how to correctly repair and restore these fragile works of art, and if you try to do it yourself, you may end up doing further damage that could completely devalue and even destroy the work. Some damages can never be repaired. Even a professional conservator cannot bring back faded pigments to their original brilliance or do more than minimize a severe amount of staining. So it is important for anyone who owns works on paper to do their part in preventing these common types of irreparable damage.
Handling. As much as possible, do not handle the work of art on paper unless you are in the process of framing it, and then hold it carefully by the edges. Wear gloves when possible to prevent finger prints and the transfer of moisture and oils from your skin that can damage the paper and the art. In particular, do not touch the surface of pastel or charcoal drawings, as they can be easily smudged and damaged.
Mounting. Select a mat (window mount) in a size that is at least two inches larger all around than the work on paper itself. This will make the mounting easier while preventing the art from coming into direct contact with the wood in the frame. The mat and its backing (the under mount between the art and the backboard of the frame) should be made of 100% cotton museum board or conservation board. If you are not going to use a mat (close framing), you will still need some kind of spacer to keep the art from coming into contact with the glass. Be sure that the art is attached to the backing and not to the mat, and attach it with Japanese white paper hinges, on the top edge only, using wheat or rice starch paste or sodium carboxymethylcellulose (sodium CMC). Do not use any form of pressure-sensitive or self-adhesive tape such as cellophane tape, as these cause permanent damage to works on paper.
Framing. Frames should always be deep enough (have a deep enough rebate) to accommodate all the various layers of glass, mats, backings, and the art work that they hold. Use UV filtering glass or Plexiglas. Glass is preferred because it does not scratch the way Plexiglas and acrylic glazes do. Plexiglas and other plastic glazes should not be used when framing charcoal or pastel drawings, as the static these materials produce can damage the work. The backboard should be acid-free conservation backboard, held in place with framer’s points, and sealed with gummed paper tape. To protect the wall from damage by the frame, pads can be applied at the lower corners. Any identifying information or provenance should be attached to the backboard. Whatever type of hardware you use to hang your framed art should be strong enough to hold the weight of the frame and its contents.
Displaying. Always keep your framed works on paper away from daylight, in particular the harsh southern exposure. Avoid using spotlights on the work and instead use minimal lighting with UV filtering that is on only while viewing. You can also use LED lighting at low wattage. Do not hang art on the inside of an outer wall where the cooler wall temperature can create an environment for the growth of mildew and mold within the frame. At the same time, don’t hang near heating vents or harsh indoor lighting that will make the room too dry and warm, causing the paper to become brittle. In general, the ideal conditions for works on paper are temperatures somewhere in the range of 62°-68°F (16°-20°C), and relative humidity of about 50-60% — probably a little too cool and too dry for optimum human comfort. But, if a room is reasonably comfortable for a human being, it will probably be suitable for most works on paper. Just do your best to keep the temperature and humidity in the same range, all day, every day, and avoid any extreme highs or lows such as turning off the heat at night or when you’re away from home, or cranking it up full blast to take the chill off the room when you return.
Storing. Any works on paper that are not being framed or displayed should be stored flat in an architectural file cabinet or in custom-sized Solander boxes. The latter are composed of acid-free archival materials and some come with polyethylene (polythene) barriers between their wood frames and acid-free linings. In addition, the individual items stored in the cabinet or boxes can be mounted or matted and/or placed in their own protective folders (not plastic sleeves) or between sheets of acid-free tissue. Charcoal and pastel drawings are best stored framed. The cabinet and the boxes should be stored horizontally (flat) in the same environmental conditions as their framed and displayed counterparts. Avoid storing them in attics, basements, or garages, and check on them regularly to make sure no damage is occurring.
Summary
Prevent damage to your works of art on paper by proper handling, framing, and storage, and you will ensure the preservation of both the beauty and the value of your art investment.
This article last updated: 03/10/2015.
