Nanoparticles for Cultural Heritage Conservation: Calcium and Barium Hydroxide Nanoparticles for Wall Painting Consolidation

Abstract

Nanotechnology provides new concepts and materials for the consolidation and protection of wall paintings. In particular, humble calcium and barium hydroxide nanoparticles offer a versatile and highly efficient tool to combat the main degradation processes altering wall paintings. Clear example of the efficacy and potentiality of nanotechnology is represented by the conservation in situ of Maya wall paintings in the archaeological area in Calakmul (Mexico).

Performance evaluation of commercial nanolime as a consolidant for friable lime-based plaster

“…Although ideal particle size distribution could be obtained through a different synthesis process, the nano calcium hydroxide is generally highly unstable in water because of its tendency to aggregate in water (Giorgi et al, 2010). Whereas in short chain alcohol solvents, the nano calcium hydroxide obtains a kinetically stable dispersion (Giorgi et al, 2010).…”

“…Whereas in short chain alcohol solvents, the nano calcium hydroxide obtains a kinetically stable dispersion (Giorgi et al, 2010). The kinetic stability of the dispersion is generally proportional to the thickness of the hydrophobic layer on the calcium hydroxide particles with adsorbed alcohol, which is enhanced by n-propanol, ethanol, and isopropanol (Ambrosi et al, 2001 b).…”

“…Nanolime can be successfully used in a humid environment and consolidation using a commercial nanolime may have a moderate effect on the deterioration of historic materials caused by salt crystallization (Giorgi et al, 2010;Zornona-Indart et al, 2012;Ruffolo et al, 2014). To enhance the consolidation efficiency of the nanolime, it is recommended to identify salts and treat them accordingly using barium hydroxide nanoparticles (Giorgi et al, 2010), or alcoholic dispersion of strontium hydroxide (Gregorio, 2010).…”

“…To enhance the consolidation efficiency of the nanolime, it is recommended to identify salts and treat them accordingly using barium hydroxide nanoparticles (Giorgi et al, 2010), or alcoholic dispersion of strontium hydroxide (Gregorio, 2010).…”

Barium bright and heavy

“…On mixing it with an ammonium salt, for example ammonium chloride, a strongly endothermic reaction occurs between the two solids that produces a liquid (BaCl 2 and water) and gaseous ammonia; water placed under the reaction vessel will freeze -making for a striking demonstration experiment. Ba(OH) 2 is also used as a strong base (pK B of -2) in organic synthesis to hydrolyse esters and nitriles 4 ; as nanoparticles it is used to restore old wall frescoes by combating gypsum (calcium sulfate) through barium sulfate formation 5 . This method, developed after a catastrophic flood in Florence in 1966, has been used successfully on fourteenth-to eighteenthcentury frescoes, for example in Venice, and in the cloister of Brixen in South Tyrol, Italy.…”