This Seaweed Gel May Be The Best Way To Clean Old Buildings

It's amazing what a little agar can do.

Clean stone

(A) shows the border between cleaned and uncleaned stone surface. The location of the area is shown by the white arrow in (B).Gulotta et al. / Heritage Science

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:

[Study author Davide] Gulotta explains that the agar gel works so well because it has a well-ordered microstructure with a high number of pores that are evenly distributed, which enhance water retention and allow liquid water migration within the gel. When agar is applied as a water-based poultice, the solvent effect of water is promoted: in the presence of soluble deposits the dissolution is favoured and the dissolved material is drained into the gel structure, effectively soaking it up like sponge.

Researchers also found that they could add soaps and chelating agents to the gel to tailor it to specific areas of stone.

Microscopic cleaning

Gulotta et al. Heritage Science