Petz Scholtus in a June 21, 2012 posting on the Treehugger website has featured an item about nanotechnology and stone (Note: I have removed a link from the excerpt),

Tecnadis PRS Effect is a water-repellent for facades and historical monuments based on nanoparticles. It is being tested on the Cathedral of Santiago de Compostela to prevent the porous stone from absorbing water and humidity, and hence, to make it last longer. What makes this especially suitable for heritage conservation is the fact that it does not close the pores of the stone but instead, lets it breathe.

Here’s a company demonstration of  water being poured on a stone that has been treated with the product (silent with Spanish language titles),

I last posted about Spain, nanotechnology, and heritage conservation efforts in a June 7, 2011 posting about the murals of the Church of Santos Juanes.