How to Preserve Anime Cels
Cel preservation is important and tedious. Below are my two cents based on my own research with actionable links to protect your collection.
Cels Preservation
At a high level…
Environment
Cels are extremely sensitive to high temperature and humidity. Like all things, they are slowly decaying and that process is greatly accelerated through their exposure to UV light or lack of air circulation (whereby the toxins they emit build up and accelerate their decomposition, much like tooth decay).
According to the American Institute of Conservation (link), Walt Disney Company preserves their collection in the following conditions:
“The environmental conditions are set to 62–65 F (16-18 C) and 50% (1/− 2%) relative humidity. Cels are interleaved with 2 mil polyethylene sheets and kept in archival boxes… exposure to light in every storage location has been limited.”
Handling
Keep cels flat and never bend or roll them to avoid cracking the paint. Never handle with your bare hands (because of oils, wear cotton gloves instead). Don’t try cleaning them with chemicals or water, if you must wipe them, use cotton or microfiber.
Storage
The research here is a bit mixed. Several papers suggest Cels can safely be stored in acid-free Glassine envelopes. Another indicates it uses polyethylene. Key takeaways: Cels should never touch other cels because of sticking. All materials used should be acid free. My digging into glassine vs polyethylene (no sources provided) suggests glassine is not recommended for long term storage. Between polyethylene and polypropylene, it appears polypropylene is superior, which is what I’ve decided to go with. Last point: Cels need to air out to release their toxins, so ensure the bags are not sealed and instead cut the corners and the top to allow some flow and air them out at least once a year.
What you need to buy
Below are a few items you should consider buying (these are not affiliate links):
White cotton gloves to handle your cels (link) (~$10)
Acid-aree polypropylene inserts for the cels themselves
BCW Treasury Resealable Comic Book Bags (10.5” x 13.5”) (link) (~$20)
Acid-free storage book / portfolio case (for less valuable cels)
Itoya Portfolio Series Art Presentation Portfolio (11” x 14”) (link) (~$20)
Acid-free tissue to absorb toxins (placed between polypropylene inserts pages)
Acid-free storage case (for more valuable cels; never more than 5x per case)
Temperature and humidity cabinet (more cost effective than worrying / running A/C)
Available on Amazon, find one that fits your cels and meets your budget
Additional Reading Material
For those of you disinclined to trust blogs, forums and Facebook groups (like me), below are two research papers that discuss animation cel conservation and provide detailed descriptions of Disney’s practices:
[1] Animation Cels: Conservation and Storage Issues (2014 by K McCormick, M Schilling, M T Giachet for the American Institute of Conservation)
Environment: “Since 1999, the [Walt Disney Collection] environmental conditions are set to 62–65F and 50% (1/− 2%) relative humidity. Cels are interleaved with 2 mil polyethylene sheets and kept in archival boxes. It is worth noting that exposure to light in every storage location has been limited.
Measuring decay: “Of the many indicators of cellulose acetate degradation, perhaps the most noticeable in cel storage cases is the odor of acetic acid, formed by hydrolysis and off-gassing. A-D strips, developed by The Image Permanence Institute (IPI), are a reliable tool for identifying so-called Vinegar Syndrome in cellulose acetate film and in other forms of cellulose acetate (Image Permanence Institute 2001). A-D strips turn from blue to green to yellow with increased concentration of acetic acid.”
Framing: Passe-partout mounts, typically used for works on paper to produce a microclimate for the artwork inside of a mat package, are used routinely at the ARL for displaying cels on loan to museum exhibits. The mounting process starts with hinging the artwork as desired, generally with Japanese tissue hinges attached using methyl cellulose or wheat starch paste, onto 8-ply acid free mat board. On the verso of the mat board, a sheet of Art-Sorb is applied with 3M ATG 987 Adhesive Transfer Tape. A Sud-Chemie Performance Packaging humidity indicator card is also adhered to a visible corner of the Art-Sorb. A sheet of .003 mil polyester is cut to fix the size of the mat board. The passe-partout package is then assembled placing the layers one by one face down on each other starting with the UV acrylic (Plexiglas), then the matted artwork with the Art-Sorb backing, followed by a sheet of polyester. The layers are sandwiched together using Scotch 845 Book Tape. The tape attaches to the front edge of the acrylic glass and continues along the side of the packet taking in all the layers wrapping around to the polyester sheet on the back. A bone folder is used to press out all air bubbles along the tape to create as airtight of a seal as possible. The passe-partout package is then placed in a frame with an archival foam core backer. A small window is cut out of the foam core to facilitate reading the humidity indicator card. The color changes of the humidity indicator card are recorded periodically. Figure 1 shows the layout of the passe-partout packages.
[2] Management and Preservation of Animation Cels in Archives, Libraries, and Museums in the United States (2018 by Angela René Schwarz at UCLA)
Interesting fact: “As multi-plane cameras had up to seven layers, each layer will have different components for characters and scene action in one picture of a scene that includes twenty-four pictures to complete a scene. In general, the second layer was considered the key element as it had the most action of the scene and would be used more than other cel layers. This makes the key animation cels more valuable than a first or third layer which may have an arm or leg for movement. There are numerous published works that further explain the animation process.”
Handling: “Administer conservative general care practices for animation cels. All repositories suggest wearing gloves when handling animation cels to prevent fingerprints on the plastic support. Should cels need to have fingerprints or dust cleaned from the image, a soft cotton cloth can be used to lightly rub fingerprints and to remove dirt from the plastic support. Never use the cloth on the paint as the cloth can rub the delaminated or fragile paint off. As the paint is water-soluble, using water on or near animation cels should be prohibited to prevent any chance of water spilling onto the cels and re-wetting the paint causing it to dilute or smear. Cels need to remain flat to prevent paint from cracking or otherwise degrading.”
Humidity absorption: “There is no way to prevent the natural deterioration process of organic material like cellulose or ingredients in the paint, but methods can be used to slow the progress of degradation. Repositories can use archival materials that have silica gel in the material, such as Artsorb, to minimize exposure to humidity; archival matboard with molecular traps using zeolites can also be used to reduce the buildup of off-gassing”
Placement: “Animation cels are not like other graphic and art materials and would be best preserved if individual cels were placed in window mats to allow off-gassing to escape and support the animation cel on a flat surface. Then a handful of cels in mats can be placed in flat boxes to be stored on the shelf. This will reduce the pressure and friction on the image of each animation cel. Special care needs to be taken with the paint, in particular when dealing with unstable paint or humid conditions. The paint will absorb the moisture in the air becoming tacky and stick to plastic supports, other painted images and other materials. Interleaving cels with archival paper or folders, a method not typical of other collections, is highly recommended. Disney ARL uses glassine to sleeve individual animation cels and prevent them from sticking to other materials. All materials used should be of archival standard and acid-free.”
Environment: “Regulate proper environmental conditions of storage facilities for storing animation cels. Temperature, relative humidity, light, and ultraviolet energy all have degrading effects on animation cels. And being a composite object made of materials that do not have the same preservation condition requirements can make it difficult to protect animation cels from these effects. In previous years the temperature used for animation cels were the low 60°’s Fahrenheit or below that are used for film and photography to preserve the plastic support. Current research suggests that a higher temperature closer to that for paintings is ideal for animation cels’ multiple components. This temperature range is 68°F to 72°F. While the temperature for paintings is too warm for the plastic, a comparable temperature for animation cels would be a range of 60°F to 65°F, preferably closer to 65°F. Relative humidity (RH) is much the same story. Animation cels have been stored at an RH of 50% or lower all to preserve the plastic support. However, research conducted in the Disney ARL and GCI project indicate that the ideal RH for animation cels to preserve the plastic and the paint is closer to 55% to 60% relative humidity (Beltran, 2017). This allows the air to retain enough moisture to keep the paint from drying out and cracking, but not so moist as to cause the plastic support to start warping. Essential preservation when using temperature and relative humidity is the stability of these conditions as temperature affects relative humidity. However, if a choice has to be made between maintaining the relative humidity or temperature, maintaining the relative humidity is best.”
[3] Animation Cel Storage and Preservation: Caring for a Unique American Art Form (2007 K Saracino JFK University)
“With these standards in mind, Witkowski provides general care guidelines for animation cels. The first step is to properly handle animation cels by wearing cotton gloves and to handle them by their edges, remembering never to roll or bend the cels as this could cause paint to crack and flake off. The second step is to avoid getting water on a painted cel. Because many of the paints used were water-soluble and earlier cels were meant to be washed off, water should never encounter the paint. Witkowski recommends using a soft, dry, cotton cloth to remove any dirt or fingerprints, avoiding painted areas, and applying minimum pressure. Rub the cloth horizontally over the cel, avoiding the use of compressed air as it may blow off paint. The third step in caring for animation cels is to remove cellulose nitrate cels from their storage or framing environment once a year to air out completely, for a period up to 24 – 48 hours.”
“Witkowski goes on to recommend storage for animation cels. Her first recommendation is to store unframed animation cels flat. She also recommends against placing polyester such as Mylar® and Mellinex®, or acetate sheets directly against water-based painted cels. The paint on the cel can stick to the polyester sheet or acetate sheet if it gets too humid. Her second recommendation is to place unframed animation cels between a folded leaf of acid-free glassine, then place the wrapped cel in an acid- free Solander® box or in a similar acid-free box with acid-free tape. She also suggests stacking no more than five cels of the same size on top of each other.”
“In S/R Lab Notes, “No. 1: On the Subject of Caring for Animation Art,” Stark lists general care guidelines. The first guideline is to control light levels by never hanging art in direct sunlight or too close to a light source. The second is to control temperature and RH by never hanging art in extreme temperatures and a constantly changing environment. The third is to examine art at least every three to four months. The fourth guideline is to store art in an envelope, lying flat with no other weight on top. Stark recommends no more than 10 – 15 cels stacked on top of each other, separating the cels with clean paper and avoiding plastic wrap.”
“Specific care for animation cels is also noted by Stark. The first step to cel care is to never roll or flex a cel. He also recommends washing your hands, and handling cels only by their edges. Cotton gloves, he adds, are also a good idea. The next step he highlights is that “cleaning is the most beneficial thing you can do to enhance the appearance and longevity of your cels.” He recommends cleaning surface debris by wiping horizontally with a clean, dry, soft cotton or flannel cloth. Unlike Witkowski, Stark condones wiping over inked or colored areas with very light pressure. The third step Stark recommends is to never use any liquid or compressed air when cleaning a cel. He instead recommends using a brush to remove light dust particles. However, he does not specify what kind of brush to use. His final recommendation is to remove cellulose nitrate cels from their frames and mounts every 12 months and air them out for 24 hours.”
[4] Unboxing Nelvana: Animation Cel Preservation and Storage for the Nelvana Animation Collection