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

The application of Ca(OH)2nanoparticles dispersed in short chain alcohols to adjust the pH ofacidic cellulosic substrates (paper, canvas, and wood) has been introduced and largely assessedin conservation practice, and commercial products are available on the market. Recently, someconcerns about this methodology were expressed in a technical note (‘A Note of Caution onthe Use of Calcium Nanoparticle Dispersions as Deacidifying Agents’by Cremonesi (2023)).The main criticism is that carbonation of the hydroxide particles into calcium carbonatecould be too slow, and the Ca(OH)2remaining on thefibers might cause structural damageto cellulose by producing high alkalinityin situ, when water absorbed by the alcoholdispersion 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 thecorrect application of the particles’dispersions results in carbonation and in neutral pHvalues in a few days; and (2) an up-to-date literature survey, in which the Ca(OH)2nanoparticles’carbonation kinetics is studied in detail, and potential structural damage tocellulosic materials in an alkaline environment is evaluated and ruled out