Worldwide film archives contain millions of film reels, including historical artifacts from the early 19th century. Preserving these films, especially considering the fading nature of color films over time, is crucial. All color films fade over time. The three color layers of the film (yellow, magenta, and cyan) lose their original colors. In some films, yellow fades first, while in others, cyan does. The fading of color layers changes the film's color balance and reduces contrast, often resulting in a pinkish tint. Heat and humidity are the main causes of film fading. Using dehumidifiers to provide dry air and maintain low dry-bulb temperatures can slow down the fading process, but this process cannot be reversed for already faded film. Digital restoration can correct the faded colors using color or density adjustment software. While the physical and chemical deterioration of film materials is inevitable, appropriate care and storage methods can slow this process. In this context, using dehumidifiers plays a critical role in preserving film archives.
Acetate film materials are particularly prone to deterioration due to a problem known as "vinegar syndrome." This condition is characterized by the film emitting an acetic acid smell, and using dehumidifiers is an effective method to prevent acetate film deterioration. In acetate-based films, "vinegar syndrome" results from the gradual breakdown of the film in humid environments, producing acetic acid. Once this process starts, the acetic acid released further accelerates deterioration, making it impossible to stop. In this form of degradation, the film base shrinks irregularly and curls horizontally and vertically, losing flexibility. The degradation of the film base also affects the emulsion, causing it to crack and peel off.
Using dehumidifiers is also important for nitrate-based films. Nitrate film bases degrade over time even under the best preservation conditions. The nitrogen dioxide gas emitted from the flammable nitrate combines with moisture in the air to form nitric acid, which degrades the emulsion and separates the base. Nitrate films require special storage conditions due to their flammability and degradation processes, and dehumidifiers ensure these films are stored safely. The ideal storage temperature for nitrate films should be kept low, as higher temperatures lead to faster degradation and increased fire risk. Therefore, the ventilation system should allow for temperature control, and fire suppression systems should be integrated with the ventilation system as part of emergency protocols.
For long-term preservation of color films, optical data, and microfilms, it is recommended to store them in controlled environments with low temperatures and low relative humidity using dehumidifiers. These conditions help prevent film fading by maintaining an indoor environment of<12-18°C dry-bulb temperature and 30% relative humidity.
Similarly, black and white films should be stored in low humidity and temperature conditions (negative b/w film:<18°C dry-bulb temperature and 30% relative humidity). In this case, dehumidifiers provide an ideal solution for long-term preservation without degradation. In general, humidity control in film archives offers advantages such as extending the lifespan of films, preserving historical records, and consuming less energy compared to traditional climate control systems. Therefore, using dehumidifiers is essential for preserving film archives.
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