| Papers are used as carrier of documents, recording knowledge by writing, printing, etc. Its durability is an important issue requiring our close attention. The main factor affecting papers'durability is acid, which makes papers brittle, yellow or dark, with significantly lower mechanical strength, unable to flip over in a more serious condition, even broken to scraps. Deacidification of acidulated documents is one of the primary problems of protection and restoration of paper documents.In this paper, natural plant extracts were taken as paper deacdification agents, which were mild and harmless to documents, environment and humans. It was observed that the pH values of natural deacidification agents were changing, and the deacidification effects were not stable during long term storage of natural deacdification agents. Mildew inhibitors were added to natural deacdification agents to stabilize natural deacidification agents. The stabilities were characterized by determination of pH values of deacidfication agents changing along with time. It showed that the natural deacidification agents added with mildew inhibitors were of more stable pH values, with a little change.Acidulated papers were immersed in natural deacidification agents, such as TS1, TS2, TS3, TS4, to be deacidfied. The deacidification effects of these four natural deacidfication agents were compared. The colors of papers before and after deacidification were measured. The impacts of temperature, time, dilution ratio on deacidification effects and color changes of paper after deacidification were investigated. The results showed that in the same conditions of times, temperatures, dilution ratios, the deacidification effects of TS3, TS4 were better. The papers turned brown slightly after deacidification with TS1, TS2, and turned grey slightly after deacidification with TS3, TS4. The deacidification effects were enhanced in higher temperature and longer deacidification time, in which the colors changed little. The deacidification effects of TS1, TS2, TS3, TS4 diluted were decreased. The deacidification effects of TS2, TS3, TS4 were sharply decreased. When the dilution ratio of water and natural deacidification agents reached 4:1, the effictivenesses were lost. The natural deacidification agents, TS1, TS2, TS3, TS4, TS6, and lime water were mixed in certain proportions. Mixture uniform design method was employed to obtain the optimal formula with the best effictiveness. It was suggested that the optimal formula was the mixture of TS1 and TS4, and TS1:TS4=0.2456:0.7544. The alkali residue of paper afer deacidification with the optimal formula was determined as 0.08mol/kg.Pressure atomized method was applied for the deacidification. The impacts of usages of natural deacidification agents on deacidification effects were studied. Various deacidification agents, such as aqueous solutions of Ca(OH)2, calcium propionate, alcohol solution of calcium propionate, iso-butylamine and TS4 were employed using pressure atomized method for deacidification, and their deacidification effects were compared. The results suggested that within small dosages ranges, the deacidification effects of natural deacidification agents increased with the dosages increased. The effectivenesses were different with different deacidification agents, among which the organic solutions were the best. Meanwhile, the advantages of pressure atomized method were as follow:non-distortion and non-adhesive of paper, non-affection on ink, fast-dried paper after deacidification; the pressure atomized method was operated in room temperature to obtain mild vapors with high content of effective components, fruitful, suitable for different types of deacidification agents; and the operation was simple.
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