Damage to great monuments is caused by air pollution besides other factors. Pollutants such as sulfur dioxide and nitrogen oxides are the most serious causes of degradation in carbonate stone, which in the form of marble, limestone and similar materials comprises some of the most important monuments and artifacts in the world. The main damage to monuments is that the stonework becomes sulphated through the transformation of calcium carbonate to calcium sulphate owing to the presence of sulphur dioxide. Two forms of deterioration then take place: the constitution of a black film in areas sheltered from the rain and crumbling of the interior of the stone. Scientists in Spain have developed a new nanotechnology material specifically suited to stone-based historical structures in the form of a crack-free gel to be introduced in the pores of the treated stone. Application of a coating to the surface of the stone totally protects it from the effects of the atmosphere around it. The product is applied in liquid form and polymerization takes place in the pores of the deteriorated stone by way of a classic sol-gel process, forming a silica network which is able to stabilize the decaying stone. The coat facilitates a deep and homogeneous penetration into the decayed substrate; humidity present in the rocks produces spontaneous gelification of the product and polymer forms oxygen-silicon bonds similar to the existing bonds in the minerals of the rocks.