BIOLOGICAL INVESTIGATION ON SIZINGS FOR PERMANENT PAPERS

We have conducted a research on the biodegradability of papers conform ing to UNI 10332 ''Carta per documenti - requisiti per la massima perm anenza e durabilita'' (Paper for documents - requirements far maximum permanence and durability) caused by the cellulolytic fungi. A particu lar importance was given to the effect of three sizings most widely us ed in the manufacture of papers intended for printing of documents, bo oks and any printed matter that for its historical, legal importance h as to be preserved for a long time. We prepared samples of paper in ac cordance with the Standard different only for the sizings. Successivel y we tested the biodegradability both of the sizings on an inert backi ng and of the samples of paper left in incubation at ranging temperatu res (20 degrees C and 30 degrees C) and relative humidity (100%, 92%, 85%, 75%, 63%, 53%) for twenty weeks. We used for the tests fungus str ains of the types most frequently isolated from paper materials. We th en studied the effect of the sizings on paper hygroscopicity and the e xisting relationships between the thermo-hygrometric values of paper i ncubation and the incidence of the spore's survival. The results obtai ned were summarized as follows: The paper conforming to UNI 10332 supp orted the fungus attack only under particularly critical thermo-hygrom etric conditions. Its neutral alkaline pH value has inhibited the grow th of most cellulolytic fungi; The accelerated ageing helped celluloly tic fungi attack because of the degrading action on the cellulose fibr es and on the sizings, despite the reduction of the moisture content a vailable to micro-organisms; The thermo-hygrometric conditions of incu bation and the accelerated ageing deeply affected the spore's life: in particular, it was pointed out that the spores survived for a longer time under the thermo-hygrometric conditions suggested for paper conse rvation; The choice of the sizings has sometimes strongly affected the paper biodegradability and its hygroscopicity: one sizing, in particu lar, was suited for the manufacture of the ''permanent paper'': paper sized with it has supported the fungus development at only 100% relati ve humidity, both before and after the accelerated ageing. We hope thi s work is a practical contribution to the choice of the sizings that f rom biological view point, are best suited for the manufacture of pape r to be preserved as long as possible.