Integrating experimental paper analysis into traditional ancient book restoration: A case study of the Chinese medical text Yi Men Pu Du

Background Ancient Chinese books represent irreplaceable cultural heritage, yet many suffer severe deterioration from acidification, insect damage, and mechanical degradation. Traditional restoration practices rely heavily on empirical experience, with limited integration of scientific testing. This study demonstrates how systematic experimental paper analysis can be embedded into the traditional restoration workflow of a critically damaged ancient Chinese medical book. Methods The ancient medical text Yi Men Pu Du (1739), classified as Grade 1 (critical) damage under Chinese heritage conservation standards, underwent comprehensive paper characterization before, during, and after restoration. Fiber composition was identified by optical microscopy (GB/T 4688–2020). Physical properties—grammage (ISO 536:2012), thickness (GB/T 451.3-2008), and tensile strength (GB/T 22898–2008)—were measured for both original and repair papers. Surface and cold-extraction pH were determined (GB/T 13528–2015; GB/T 1545–2008). A Ca(OH) 2 deacidification protocol (1 g:200 ml) was applied in three successive stages. Results Fiber analysis revealed 100% bark fiber in the cover and 100% bamboo fiber in the text leaves, directly guiding repair paper selection. Pre-restoration surface pH ranged from 5.1 to 5.4, confirming severe acidification. Progressive deacidification raised pH to 7.4–7.7. Thickness monitoring identified excessive post-restoration thickness (195 μm) caused by overly concentrated pulp, which was resolved by reducing the pulp ratio from 5 g/400 ml to 0.5 g/400 ml. Bamboo repair paper exhibited 29.95%–36.66% higher longitudinal tensile strength than bark papers. Conclusion Systematic experimental analysis transformed an experience-based restoration into an evidence-based practice, providing quantitative guidance for material selection, deacidification, and process optimization. This methodological framework is transferable to other ancient book conservation projects.