Paper and paper-based cultural artifacts gradually undergo acid hydrolysis degradation during prolonged use or storage, ultimately leading to structural failure and loss of value. Assessing the condition of paper based on its acidification level and degradation trends facilitates targeted deacidification conservation strategies. Given that the inherent pH of paper is a critical factor influencing its degradation, this study focuses on 1990s machine-made paper as the research subject, employing gel permeation chromatography (GPC) to investigate the acidification tendencies and degradation rate constants of papers with varying initial pH values under artificial dry-heat accelerated aging conditions. Non-destructive characterization methods were further employed to analyze changes in comprehensive paper properties, including pH, oxidation degree, and color difference. Results from the 90 d accelerated dry-heat aging experiment revealed that the degradation of the studied machine-made paper follows first-order degradation kinetics. Alkaline paper exhibited smaller degradation rate constants and slower degradation rates. Acidic machine-made paper demonstrated rapid pH decline, significant oxidation and visible darkening/yellowing, while alkaline machine-made paper maintained an alkaline to nearly neutral state, with a lower oxidation degree and a smaller color difference. However, regardless of whether it is subjected to strong alkaline or strong acidic treatment, extreme acidic or alkaline environments will lead to a decline in the degree of polymerization of cellulose in the paper. The optimal pH range for this machine-made paper was identified as 7~8.5. Building on these findings, a theoretical calculation method for alkali dosage in deacidification is proposed. By considering the appropriate pH range under acidifica- tion degradation trends, the alkali dosage is decomposed into acid neutralization amount and alkali retention amount for analysis, with calculation formulas provided for different deacidification targets. This research can be extended to degradation trend analyses of other paper types, while the alkali dosage calculation provides a reference for practical deacidification processes to avoid secondary damage caused by excessive alkalinity.

Key words: machine-made paper, pH, acidizing degradation rate constant, suitable pH value for deacidification, calculation of alkali dosage in deacidification