In restoration of the masonry, it is important to maintain its original composition and appearance by matching historical materials with appropriate material which is consistent both visually and in accordance with physical and chemical properties. Materials of historic-cultural and artistic monuments are constantly exposed to disintegration processes which are accelerated by everincreasing environmental pollution (NxOy, SO2, CO and CO2). This environmental pollution reacts with moisture from air and causes acid rain. As a result, watersoluble salts (most commonly sodium, potassium and magnesium sulphates, and gypsum) are formed, causing the chemical corrosion of the masonry, which can cause its disintegration. The earliest research on corrosion of masonry and of natural stone materials in Latvia was conducted in 1984 at the Department of Silicate Technologies, Riga Technical University. In 1995 the Center for Conservation and Restoration of Stone Materials was established at the Institute of Silicate Materials, Riga Technical University. Research by the Center includes scientific analyses of cultural-historical monuments – the study of the composition, structure, physical, and mechanical properties of corroding materials.