Microfilm must be exposed, processed, and stored according to international standards (see Reformatting). Housing begins with the film being wound onto noncorrosive metal or plastic reels covered with a strip of acid-free paper secured by string ties or Velcro strips. Rubber bands should not be used. The boxes in which the full reel is stored should be made from acid-free board/paper and designed like those recommended for paper. Inert plastic containers are also acceptable storage boxes.

International standards

Most funding agencies require that international standards be followed when research materials are microfilmed with their support. Among other requirements, three generations of film must be produced: the camera or "master" negative, the print negative, and a positive copy. The camera negative must be stored in a low, even temperature and low humidity, ideally in a location remote from the other film generations, and should not be used except under emergency conditions. The filming library or archive should maintain the print negative in good storage conditions and use it for making positive copies on demand. The positive copies are for reader use.

Film deterioration

The inability of many libraries and archives in tropical regions to provide appropriate storage conditions of microfilm negatives is of great concern. Although film produced and stored correctly is known to last for a minimum of 500 years, film in some countries has become unreadable after only twenty years in conditions of high temperature and humidity. In some cases, governments and institutions are reluctant to allow film negatives or copies to leave the country, even though this can spell the end of the film. The solution may be for institutions to cooperate on film storage, perhaps with a commercial company or institution in a temperate country, or through a regional consortium of institutions.

One system is hermetic sealing, which is under stringent investigation by the Image Permanence Institute and Cornell University. This process involves sealing packaged microfilm in a pouch purged of oxygen in a system similar to the sealing of dried food. The research will help to determine whether hermetic sealing can be designed to preserve and protect microfilm for long periods without a cold storage vault.