Nanoparticle Protection

New inorganic nanoparticles that simultaneously restore and preserve ancient artworks have been developed by researchers in Italy. Many types of cultural heritage could be treated using this method, without causing further damage over time unlike some currently used restoration techniques and polymer coatings.

Preserving history

Preservation and restoration of artwork is important, as paintings such as frescos – Italian wall paintings applied straight onto plaster – give us important glimpses into history. A standard method used by conservators for protecting frescos is to apply an acrylic polymer coating, but such coatings can turn yellow, giving the surface a plastic appearance and damaging the artwork in the long term.

Piero Baglioni and colleagues at the University of Florence in Italy, have developed alkali metal hydroxide nanoparticles that can be applied to frescos and other pieces of art that not only provide a protective barrier against further damage, but can also help restore them to their former glory.

Baglioni explains that most wall paintings and monuments are made out of limestone – a sedimentary rock composed largely of calcium carbonate. When damaged by water, ‘calcium carbonate is chemically converted into calcium sulfate and during this reaction you lose the painting,’ Baglioni continues.

Baglioni’s team has developed calcium hydroxide nanoparticles that react with carbon dioxide in the air to form calcium carbonate, replacing the calcium carbonate that has been lost due to water damage. This extra calcium carbonate can also help to reverse some of the damage caused by the calcium sulphate, something that none of the current coatings are able to do.

The nanoparticle coating that Baglioni’s team has developed is very easy to use. The nanoparticles are first dispersed in propanol and then the propanol suspension is sprayed or brushed onto the surface of the artwork. In cases where the surface is very fragile, Japanese paper – a fine paper with pores – is laid on top of the painting to protect it from damage, allowing a thin coating to be applied through the paper onto the fragile image beneath.

Large potential

‘We produced calcium, strontium, barium and magnesium hydroxide nanoparticles, and each of these are useful for different purposes. For example, you can use magnesium and calcium hydroxide for the conservation of paper, wood or cellulosic based materials,’ Baglioni states. He believes the nanoparticle method can be used to protect most surfaces, apart from metal.

The spray can also be used in remote places where there is no electricity, and Baglioni has used his method in the jungle in Mexico. ‘Hopefully, eventually all conservators will use this method as it is simpler and safer for the works of art and the conservator,’ Baglioni concludes.

Originally published in Infochem