A team from UNSW Sydney and the University of Bologna have discovered a new approach to preserve marble, with a number of organic solvents found to have enhanced the materials’ resilience.
The team combined computational modelling with experimental methods including ethanol, isopropanol and acetone on carrara marble.
“Most of us are familiar with some iconic marble works of great historical and cultural significance,” says UNSW Science Lecturer and study Senior Author, Martina Lessio.
“We’re working to find ways to help preserve these works for future generations so they can have the chance to enjoy and appreciate them just like us.”
The study was completed after a new treatment was created by conservation scientists that improves the material’s resistance to rain. The treatment, comprising calcium phosphate, forms a protective coating that waterproofs the marble without causing discolouration or aesthetic change.
Lessio says that the improvement in resilience that the marble gained from the treatment was unclear.
“Finding out the reason it’s behaving this way is critical to be able to select the best possible solvent for the treatment and maximise the protective efficacy,” she says.
“Computational tools allow us to investigate the fundamental chemistry behind these observations. Combined with experimental insights, we can better understand how these organic solvents work at the molecular level and develop a rational design for the marble conservation treatment.”
Researchers from the pair of universities tested the adsorption of ethanol, isopropanol and acetone on the calcite surface of a Carrara marble sample. They first simulated the interaction between the different solvents and the surface through computer modelling. Four different conditions were tested: water, ethanol, isopropanol and acetone, with the samples treated by immersion in separate beakers containing 100 mL of an aqueous solution of a phosphate precursor, with and without the organic additives.
Each solvent was unique in the way that it responded to the marble surface. Each improved the protective performance, with the alcohols both forming a water-repellent layer, while the acetone formed a mixed, dynamic layer.
“It was surprising and intriguing to us that all solvents favour the formation of a protective calcium phosphate layer, particularly acetone, which has very different chemical properties from the other solvents tested,” Lessio says.
“It suggests when selecting a solvent to optimise the marble conservation treatment, the solvent behaviour at the surface is not a critical factor to consider like we thought.”
Lessio says the next stage of the research will test other factors and whether there are other aspects of the solvents that are responsible for the marble’s resilience.
“So far, we have only investigated one aspect – the behaviour of the solvent at the surface. But other factors need to be investigated, like the behaviour of the solvent in solution, and computational work is currently in progress in our group to uncover this,” she says.
To read the study, click here.
