Volume 8, Number 4
Jul 1984

More About Gamma Rays

Stuart Kohler recently did a literature search on gamma radiation sterilization of paper. The four references that he found are listed here.

P. Calvini and L. Santucci, "Alcuni dati sugli effetti dell'irradiazione gamma sulla carts." Bollettino Dell'istituto Centrale per la Patologia del Libro 35: 55-62, 1978-79.

Samples of a 17th century rag paper and Whatman No. 1 chromatographic paper were tested for changes in degree of polymerization, alpha-cellulose content, pH, brightness, tensile strength, folding endurance and crystallinity, following irradiation and accelerated aging. Since minimum doses for satisfactory disinfection had been established to be in the whereabouts of 005 Mrad, the results of our chemical tests advise against this kind of application. (from authors' abstract)

Sara C. Pavon Flores, "Gamma Radiation as Fungicide and its Effect on Paper." Bulletin of the AIC 16: 15- 44, Winter 1975-76.

Conclusions [as edited and even interpreted to make it intelligible; best refer to the original if possible -ed.]: The principal purpose of our work was to establish conditions for fungicidal use of gamma rays. Our studies show that the lethal dose for the irradiated fungus is 1.8 Mrad to 500 Krad/h.

As a second objective we studied the effect of this lethal dose on modern papers of different compositions. Even though mechanical resistance of the group of these papers did not present considerables modifications before the gamma rays, the decrease of enough importance of its chemical index specially of those with a high proportion of wood pulp shows that, under experimental conditions, irradiation has a fatal action on the internal structure of those papers. [First five lines of the foregoing sentence are left in their original form, because the meaning was not clear. -ed.] Nevertheless, papers containing a great quantity of noncellulosic products, such as newspaper, reacted very well, especially before artificial aging.

Because of this, and under actual operating conditions, the systematic use of the gamma radiations as fungicidal treatment does not seem adequate.

Nevertheless, we are certain that this technique could find practical applications for the disinfecting of certain types of graphic documents, once the suggested experiments have been completed. For instance, better results might be obtained by irradiating the papers in an atmosphere that contains nitrogen, or else lowering the lethal dose by a combination of temperature and a fungicidal gas, during irradiation.

Finally, this series of tests should be tried on naturally aged and moldy paper.

Jack Hillend and H. Swenson, "Electron Radiation of Aqueous Methyl Cellulose Solutions." Journal of Polymer Science: Part A 2: 4921-4930, 1964. Also of interest, though electron radiation is different from gamma radiation.

T. A. Roberts, "Recovering Spores Damaged by Heat, Ionizing Radiations or Ethylene Oxide." Journal of Applied Bacteriology 33 (1): 74-94, March 1970.