1.1 This specification covers file folders used in the storage of records and documents that are expected to have maximum, or substantial, life expectancy.
1.2 It has been shown (1, 2, 3, 4, 5) that the life expectancy of paper is at least an approximate function of the pH of an aqueous extract of the paper. Three pH levels, reflecting three levels of life expectancy, are specified.
1.3 The following would be expected to contribute significantly to the life and usefulness of folders: the use of folders with controlled acidity, or of folders manufactured under neutral or alkaline conditions, especially with an alkaline filler, such as calcium carbonate, that absorbs acidic gases from the atmosphere and can neutralize acidic materials formed during aging.
1.4 This specification is based on fiber sources used in the production of paper that contains no more than 1% lignin, for papers used in archives, libraries, and other permanent records. However, under proper conditions, (see X1.5), fiber sources containing more than 1% lignin may be employed for many other end uses in paper for records that are required to have a substantial life expectancy.