CO2 snow microblasting of submicron particles from cellulose-based cultural heritage objects: Comparison with traditional dry cleaning methods

Indoor air pollution in libraries and archives can pose a serious risk to the objects stored there. The harmful effects of most gaseous pollutants are well described; however, much less is known about particles. Aerosol particles cover an extensive range of sizes and have variable compositions. These properties then determine their possible influence on the degradation of materials. Coarse particles (> 1 μm) can be generated directly indoors. These sources are mainly visitors, object handling, cleaning, and construction work. Fine particles (< 1 μm) penetrate dominantly from the outdoor air and originate primarily from diesel engine emissions and domestic heating. Particulate matter poses a significant risk to library collections, mostly made from porous cellulose-based materials such as paper and textiles. Fine particles, representing up to 90% of the particle mass in libraries and archives, deposit on the book surfaces and penetrate small openings, including inter-fibre spaces. These particles primarily cause soiling and darkening of surfaces, but they can also cause chemical degradation or moistening; therefore, cleaning them is necessary.

Our study aimed to verify a newly developed automatic cleaning method using a two-phase spray of CO₂ microparticles in a carrier gas stream. The results were compared with six traditional mechanical cleaning techniques. Measurements included an assessment of particle removal efficiency and possible degradation of library materials. The method was subsequently verified using real archival documents. The results showed that the spray effectively removed fine particles, including those deposited on the fibrous surface. The treatment did not change the surface properties of uncoated papers and textiles. In contrast, all studied traditional mechanical cleaning methods were ineffective for fine particles. Moreover, the mechanical techniques alter the surface by leaving visible crumbs of the cleaning material, releasing fibers, and changing the fiber’s structure. The results indicate that cleaning using the automatic system suits common types of paper and textiles stored in library collections.

• Mašková L.*, Smolík J., Vávrová P., Neoralová J., Novotná D., Jandová V., Ondráček J., Kocová K., Marešová A., Zedníková M., Schwarz J. CO2 snow microblasting of submicron particles from cellulose-based cultural heritage objects: Comparison with traditional dry cleaning methods. J. Cult. Herit. 2024, 70(Nov-Dec 2024), 1-11. doi: 10.1016/j.culher.2024.08.008