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Original protective renderings have been the focus of numerous studies in recent years. Relevant literature, archival research and archaeological findings reveal that a number of mortar mixes or liquid substances were brushed on to protect and colour-unify the exterior ashlar-stone of many historic buildings. These coatings were of two types: common mortars, particularly improved with organic additives, and water-resistant filmforming substances. Economic cost, local supply, traditional practices and technological development are vital to an understanding of regional preferences for one mortar mix or material over another. The Cathedral of Leon is a mediaeval gothic temple from the thirteenth century, profusely remodelled throughout its history. In the sixteenth century, a new design of the courtyard partially enclosed a fifteenth-century exterior wall. Samples from the enclosed and exposed parts of this wall were examined. Analytical research suggests that the stone surface of this element received a treatment based on gypsum with organic additives. These organic products were fatty materials of the lipid type (tallow or lard) which reacted to form an insoluble, hydrophobic soap, at the same time providing the stone with its yellowish colour. The exceptional amount oflime registered in samples from the enclosed section has been considered a component of this surface treatment. [ABSTRACT FROM AUTHOR]

The article discusses the pigments used on a door on the north portal in the cathedral of León, Spain. Topics discussed include the use of microchemical testing to study the pigments, attempts to determine the age of the decorations on the door, and the additions over time of religious sculpture to the portal.