Condition is one of the most important considerations to a print collector. Below are several common condition problems and their causes. Many of these problems can be lessened or eliminated by a qualified paper conservator. The American Institute for Conservation offers a free referral service to help you find a conservator in your area.
Toning, or browning, occurs when a print comes into contact with an acidic material, such as non-archival matboard. Over time, the acids present in non-archival framing materials will migrate into a print. These acids react with the paper fibers, turning them brown and weakening the chemical bonds that hold the paper together. After extensive acid damage, the paper will not only become brown, but also very brittle. Toning is heightened by sunlight exposure, because the energy in light accelerates this acidic reaction.
A common type of toning damage is "matburn", or brown staining around the edges of a print where it was covered by a mat. (ex. 1) You may also see prints with the opposite pattern, in which the entire image is browned except the mat-covered edges. (ex. 2) In this case, which has no convenient name, the acids in the backing board are responsible for the toning. The reverse side of the paper will also be toned, because the acids migrated through the back to the front.
It is important to use only archival framing materials to prevent toning. If the edge of a mat is starting to turn brown, that indicates that the mat is not acid-free. The print should be reframed with acid-free materials to preserve the print and prevent further damage.
Foxing is caused by the growth of mold on paper. It consists of tiny spots which can range in color from light brown to black. (ex. 3) Mold spores are always present in the atmosphere, but they will not attack paper unless the conditions are favorable for growth, including high relative humidity. Prints should be kept in a room with less than 50% relative humidity to prevent mold growth. In addition, prints should not be framed directly against glass as moisture can accumulate causing foxing and other damage. It is important to use a mat for proper air circulation. For more information about mold, read "Mold and Mildew: Prevention of Microorganism Growth" by the National Park Service.
Fading is caused by exposure to sunlight. The energy in light breaks down many pigments, causing them to change color and lose their intensity over time. Certain green inks tend to turn blue, while reds and yellows lighten. Some colors are particularly "fugitive", or unstable, and fade after only a short exposure to light. Once a print has been faded, there is no way to restore the original colors. For an example of fading over a relatively short period of time, check out The Fading of a Yoshitaki Print.
Some of the more dangerous UV wavelengths can be filtered out using special UV glass, and it is recommended if the print is going to be displayed. However, no glass offers complete protection. It is advisable to rotate prints in and out of display, and never to hang prints in direct sunlight.
A print with creases can often be flattened by relaxing the paper with controlled humidification and then pressing it with weights. For more information on this procedure, read "How to Flatten Folded or Rolled Paper Documents" by the National Park Service.
Do not try to flatten a creased area by directly rubbing the humidified print with a metal tool. This will compress the paper fibers and create an undesirable shiny spot. If you attempt this procedure, always use a piece of cloth or woven polyester in between the flattening tool and the paper. In most cases, creasing can only be reduced and not eliminated.
Tape residue from a non-archival mounting is commonly found on the back or front margins of a print. It can leave a permanent stain on the paper and is often difficult to remove. In most cases, it is best to leave tape removal to a qualified restorer. Tape should not be pulled off by force because this will invariably remove part of the paper, resulting in a "skinned" print. If the tape is still sticky, you may be able to gently remove it with a rubber cement eraser, also called a rubber cement pick-up. You can buy these for about a dollar at most art supply stores.
Do not use masking tape or transparent tape to mount a print because these are not archival. The recommended way to mount a print is with Japanese paper hinges and wheat paste. This causes the least harm to the print and is easily reversible. Dry mounting and wet mounting are not recommended because these methods are not easily reversed and may cause damage to the print. Not all framers use archival methods and materials, so be sure to ask questions.