A Reply to ‘A Note of Caution on the Use of Calcium Nanoparticle Dispersions as Deacidifying Agents’

ABSTRACTThe application of Ca(OH)2 nanoparticles dispersed in short chain alcohols to adjust the pH of acidic cellulosic substrates (paper, canvas, and wood) has been introduced and largely assessed in conservation practice, and commercial products are available on the market. Recently, some concerns about this methodology were expressed in a technical note (‘A Note of Caution on the Use of Calcium Nanoparticle Dispersions as Deacidifying Agents’ by Cremonesi (2023)). The main criticism is that carbonation of the hydroxide particles into calcium carbonate could be too slow, and the Ca(OH)2 remaining on the fibers might cause structural damage to cellulose by producing high alkalinity in situ, when water absorbed by the alcohol dispersion or by the cellulose-based support causes dissociation in the nanoparticles. However, in Cremonesi’s note, no accurate description of the application method was given, and some fundamental information already present in the literature was overlooked. Here, we give a rebuttal of Cremonesi’s conclusions, providing: (1) further evidence that the correct application of the particles’ dispersions results in carbonation and in neutral pH values in a few days; and (2) an up-to-date literature survey, in which the Ca(OH)2 nanoparticles’ carbonation kinetics is studied in detail, and potential structural damage to cellulosic materials in an alkaline environment is evaluated and ruled out.KEYWORDS: DeacidificationpH adjustmentpaper restorationcalcium hydroxide nanoparticles AcknowledgementsThe Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase, CSGI (Center for Colloid and Surface Science) is gratefully acknowledged for financial support.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was supported by CSGI.