Standards Development

Scope

This document specifies terminology related to the alterations of wall paintings. It is applicable to the description and classification of alterations in wall paintings found in grottoes, tombs, buildings and museums.

Purpose

This standard aims to harmonize the terminology used to describe the alterations of wall paintings, thereby strengthening the scientific basis and standardization of their conservation. It seeks to reduce the duplication of effort and the waste of resources resulting from unclear classifications or inconsistent standards among countries, improve the efficiency and effectiveness of conservation practices, and promote international cooperation and advancement in the conservation of wall paintings.

Wall paintings, which are physically dependent on built structures, consist of layers that differ in number, combination, thickness and material composition. According to their locations, wall paintings can be broadly categorized into grottoes, tomb, architectural and museum-collection wall paintings. As one of the oldest forms of human cultural expression, wall paintings embody the social and cultural contexts as well as aesthetic characteristics of different historical periods, providing valuable resources for historical studies. They possess not only historical, artistic, and educational values, but also contribute enduring momentum to global cultural dialogue and the development of a sustainable cultural economy. 

Wall paintings are numerous and widely distributed across the world. It is estimated that approximately 15% of the cultural and mixed properties inscribed on the UNESCO World Heritage List contain wall paintings. However, due to the long-term impact of natural and human factors, wall paintings commonly exhibit various forms and degrees of alteration, seriously threatening their integrity and value, making their conservation an urgent priority. Currently, the fundamental principles of wall painting conservation are becoming increasingly harmonized at the international level, and conservation practices have evolved into interdisciplinary, cross-border collaborative efforts. A notable example is the conservation project for Cave 85 at the Mogao Grottoes in Dunhuang, China, jointly carried out by the Getty Conservation Institute (USA), the Courtauld Institute of Art (UK), and the Dunhuang Academy (China), which has become a model for international cooperation in wall painting conservation.

Despite such developments, a critical barrier to international and cross-sector collaboration remains: the absence of a unified terminology system for describing alterations in wall paintings. This gives rise to two major challenges. Firstly, scholars from different disciplinary backgrounds may interpret and describe the same alteration phenomena differently in scientific research, which complicates the retrieval and comprehension of interdisciplinary and international research outcomes. This hinders the sharing of conservation knowledge and limits innovation and breakthroughs in wall painting conservation. Secondly, in practical conservation work, variations in traditional wall painting techniques across countries, combined with inconsistent terminology use among conservators, technicians and conservation specialists, often lead to communication difficulties and misunderstandings. These issues can increase operational risks during conservation work and compromise the scientific rigor and effectiveness of decision-making processes.

Unifying terminology related to the alteration of wall paintings is a fundamental prerequisite for their scientific conservation. There are several key reasons why developing an international standard for classifying the alterations of wall paintings is essential: (1) Enhancing the efficiency and effectiveness of wall painting conservation. A clear understanding of the current state of alterations is fundamental to scientific conservation. Establishing a standardized classification enables the precise identification, description, and assessment of the severity of different alteration types. This helps reduce redundancy and the waste of resources arising from ambiguous classifications or inconsistent standards among countries in alteration recognition, data processing, and technical applications. (2) Promoting standardized management of wall painting conservation. A harmonized classification system facilitates the rational allocation of conservation resources, ensures that the most severe conditions are addressed with priority, and provides a scientific foundation for understanding alteration mechanisms and developing effective preventive measures. (3) Facilitating international cooperation and collaborative innovation. A unified terminology system provides a common foundation for global communication and collaboration. It enables researchers, conservators and managers from different countries and regions to work within a shared framework, exchange research outcomes and technical expertise, and jointly address global challenges in wall painting conservation. (4) Strengthening the international regulatory framework for wall painting conservation. Many cultural heritage laws and regulations stipulate that conservation activities must be carried out in accordance with recognized standards. Developing a classification standard for alterations helps to demonstrate compliance with such legal requirements, while also providing institutional support to ensure the legitimacy, standardization, and effectiveness of conservation practices. (5) Advancing the United Nations Sustainable Development Goals (SDGs). Unifying the terminology used to describe alterations of wall paintings represents an important step towards the scientific conservation of cultural heritage and aligns closely with SDG Target 11.4: Strengthen efforts to protect and safeguard the world’s cultural and natural heritage. This standard will enhance the scientific, systematic and collaborative dimensions of global wall painting conservation. It will also promote the sharing of knowledge and resources, strengthen international cooperation in heritage conservation, and provide a solid foundation for fulfilling the collective responsibility to preserve cultural heritage and foster intercultural continuity. Based on the following considerations, the development of an international standard for the classification of wall painting alterations is also highly feasible: (1) Broad international consensus and strong demand. Wall paintings are widely distributed across the world, and their conservation has increasingly drawn the attention of governments and heritage institutions. The Principles for the Preservation and Conservation-Restoration of Wall Paintings (2003), issued by the International Council on Monuments and Sites (ICOMOS), provide a widely recognized framework for global wall painting conservation practices. In the context of globalization and growing international collaboration in the conservation of cultural heritage, there is an urgent need for a unified terminology system to describe alterations. This convergence of conceptual consensus and practical demand provides a strong foundation for mobilising international efforts to advance the development of this standard. (2) Extensive research and practical experience. Significant progress has already been made in the classification of wall painting alterations. For example, the Hornemann Institute in Germany, in collaboration with six academic institutions, carried out systematic studies on the classification of alterations in architectural wall paintings across Europe. The achievements were published in the European Illustrated Glossary of Conservation Terms for Wall Paintings and Architectural Surfaces (EwaGlos), which is available in 16 languages and successfully standardised terminology for 25 common types of wall painting alterations. Similarly, Dunhuang Academy, together with the Getty Conservation Institute, the Courtauld Institute of Art and the Tokyo National Research Institute for Cultural Properties, carried out a collaborative study on conservation standards for ancient wall paintings. The project standardized terminology for 15 typical alteration types in grotto wall paintings in Chinese, English, and Japanese. These multilingual and transnational research achievements have established a solid theoretical and practical foundation for developing an international standard on the classification of wall painting alterations. (3) Availability of existing standards for reference. At least 18 relevant standards on wall painting conservation have been issued at national or regional levels, providing valuable references for the development of an international standard. Notably, Chinese national standard, GB/T 30237-2025 Deteriorations and legends of ancient wall paintings, developed by Dunhuang Academy, presents a comprehensive classification of alteration types in wall paintings from grottoes, tombs, and museum collections. It can serve as a direct reference for the proposed international standard. In Europe, the European Committee for Standardisation (CEN) has issued a technical specification, CEN/TS 17135:2020 Conservation of cultural heritage - General terms for describing alterations to objects. It provides a broader heritage-based framework of terminology related to alteration. These existing standards offer valuable experience and support for developing an international standard on the classification of wall painting alterations.