Unless you prefer your stone monuments sooty, you’ll probably agree that it’s important to clean them. But cleaning them is tough, and often involves using solvents or scrubbing, each of which can break off chunks of stone and which may be expensive and time-consuming. A new material could change all that.
Researchers found that by merely coating stone with an agar gel, they could easily remove soot, salts, and other stuff that makes the stone appear dark and dirty. The agar, made up of polysaccharide extracted from red seaweeds, is inexpensive and very safe to work with, unlike some industrial solvents. And it does its thing rather quickly, as reported in Chemistry World. Agar is more commonly used as a substrate for growing microbes, for example in petri dishes, and is also commonly used in desserts like jellies and custards, especially in Asian cuisines.
So far, scientists from Polytechnic University of Milan have used the agar to clean the grand Milan cathedral, and the difference between clean and unclean areas is rather striking. The new cleaning method is described in a study published in the journal _Heritage Science._
How does the gel work? As Chemistry World noted:
Researchers also found that they could add soaps and chelating agents to the gel to tailor it to specific areas of stone.