Colloidal particles of Ca(OH)(2): Properties and applications to restoration of frescoes

We studied the synthesis and characterization of Ca(OH)(2) colloidal partic les and their application to the restoration of wall paintings. Submicromet er Ca(OH)(2) crystalline particles have been obtained by mixing equal volum es of NaOH and CaCl2 aqueous solutions with different degrees of supersatur ation (from 2 to 10) and in the temperature range 60-90 degreesC. The Ca(OH )(2) particles are crystalline and have the appearance of hexagonal platele ts with thicknesses of a few nanometers, as determined by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and at omic force microscopy techniques. The kinetic stability of dispersions of C a(OH)(2) particles in water and propan-1-ol has also been studied in view o f their possible application in wall painting conservation. A successful ex ample of this application to the restoration of Santi di Tito's wall painti ngs (16th century) in the Santa Maria del Fiore Cathedral in Florence is al so reported.