Abstract
Illustrated glossaries on stone pathologies help to describe deterioration forms in built heritage without resorting to any laboratory analyses. In this way, terms such as crust, deposit, and soiling which according to ICOMOS-ISCS: Illustrated Glossary on Stone Deterioration Patterns may include exogenic material, a patina which results from ageing of the material in an endogenous process, and a film included under the broad term of a coating layer in the glossary, can be macroscopically identified on site. However, a definition on the basis of characteristics only observable with the naked eye (without further analysis in the laboratory) is certainly complicated, and if in addition, the case studies are on granitic rock (a major building stone used across Europe), the picture becomes even more complicated. The intention of this brief report is to engender an open, constructive debate about the casuistry of the covering layers on granite (a poorly reactive and less porous rock) and the difficulty of using the ICOMOS nomenclature on them.
Highlights
The study of covering layers on stony materials is not new
Dorn’s proposal of terms is based on microscopic and geochemical properties: the origin of materials, aspect, thickness, and composition. This author proposed the use of the term coating to group all of the coverings together and defines the term as a “mixture of materials accreted to the rock by physicochemical processes that are often biologically mediated”, at the same time noting that the term was not standardized
The aim of the present study was to analyze the adequacy of the ICOMOS-ISCS glossary terms relating to covering layers in granitic rocks, based on the properties of this rock type. We illustrate this with six case studies taken in granite buildings of urban areas of the Galician cities of Santiago de Compostela and A Coruña, which are characterized by a temperate climate and no significantly high air pollution
Summary
The study of covering layers on stony materials is not new. As Dorn [1] remarked, there has long been historical interest in them, which deepened during the last century. A film may be opaque or translucent”; Patina is used to describe a “Chromatic modification of the material, generally resulting from natural or artificial ageing and not involving in most cases visible surface deterioration” without perceivable thickness to the naked eye and often having a favorable connotation; Soiling is used to describe a “Deposit of a very thin layer of exogenous particles (e.g., soot) giving a dirty appearance to the stone surface”. Both sources can be useful to describe covering layers on building materials. We illustrate this with six case studies taken in granite buildings of urban areas of the Galician cities of Santiago de Compostela and A Coruña, which are characterized by a temperate climate and no significantly high air pollution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
