Assessment of chromatic changes due to artificial ageing and/or conservation treatments of sandstones

Abstract

Villamayor sandstone (also known as ‘‘golden the construction of modern buildings. This stone has interesting ornamental properties, but its use also involves sandstone’’) has been widely used for construction in the city of Salamanca since Roman times. In the present certain drawbacks (a high degree of porosity, a high water imbibition coefficient, low mechanical resistance, etc.). study, the four most characteristic varieties of this material were used, considering the chromatic changes The aim of the chemical treatments to which it is sometimes subjected is to improve the properties that render brought about by consolidation and/or waterproofing treatments and by cycles of artificial ageing of natural it crumbly when challenged with humidity but without affecting its original aspect (colour, texture, etc.), thus stone and of stone subjected to these treatments. The treatments consisted of application of a consolidant at enabling it to be used in situations not normally possible, such as in window sills or any other parts of buildings different concentrations (RC 70 and 40% RC 70) and two consolidants plus waterproofing agents (RC 80 and RC where it would be exposed to frequent humidity or where 90). Artificial ageing was induced by 10 cycles of wetting/ the accumulation of water might lead to waterlogging. drying and freezing/thawing. The chromatic variations In the authors’ opinion, the treatment of this stone observed considering the E*, L*, a*, and b* parameters should not be undertaken unless absolutely necessary. were subjected to statistical analysis. q 1998 John Wiley & Their own experience and the abundant references in the Sons, Inc. Col Res Appl, 23, 46–51, 1998 literature suggest that in Mediterranean climates with a continental trend this sandstone, when properly used, gen