Red Becomes Black - and Then? Pigment Changes on Art and Cultural Heritage

Publishing Date: 26.06.2024

To mark its 25th anniversary, the Hornemann Institute of the HAWK organised a conference on chemically and physically induced pigment changes. In the record time of six months, the Institute has now published the richly illustrated conference proceedings - in figures: 208 pages with texts and 233 illustrations, tables and diagrams.

Relevant, up-to-date and interdisciplinary

The subject of pigment changes in paintings and colour settings is of great importance in the daily life of conservators, as pigment changes can fundamentally alter the original colour effect of a painting or setting. For example, the pigment red lead can change to lead oxide, turning formerly bright red areas brown or black. Owners and art history experts are alarmed because the colour changes can have a massive impact on the artistic statement or even lead to considerable colour loss. If unrecognised, pigment changes can cause misjudgements in art history, which could lead to the objects being disregarded or even lost due to a lack of appropriate care. The issue often involves momentous decisions.

Two examples of pigment changes: The bright blue pigment smalt, for example, was very popular with many famous painters in the 16th and 17th centuries, such as Veronese, Tintoretto and Rubens. Today, in some of their large-format paintings, only grey tones are visible instead of bright blue. In wall paintings, browning and blackening are frequently found today, caused primarily by chemical transformations of lead white or red lead oxides such as red lead. The result consists of dark, usually very irregular stains that make it considerably more difficult to see the shapes and colours. How do conservators deal with this problem? Reconversion is only possible in very rare cases and is ethically questionable.

The new volume focusses on material science analysis and the current restorative treatment of changes. In particular, it deals with chemically triggered pigment transformations in conjunction with external factors, such as environmental influences, and their effects on art and cultural artefacts, taking into account the effects of various conservation materials, bonding agents and coatings.

About the papers

The main novelty of the book is its interdisciplinary approach to discussing the problem, as pigment changes are of great importance for almost all areas of conservation, i.e. for painting and polychrome colour settings, from architectural surfaces to panel paintings, painting on textile supports and polychrome wooden objects to book illumination and printmaking. The topic therefore also covers almost all areas of conservation that are taught and researched at the HAWK in Hildesheim.

The introduction is preceded by two articles that use case studies to draw attention to ethical issues in conservation: At what point is a pigment change considered an aesthetic impairment of a work of art or cultural monument? Under what conditions are reconversions of colour-altered pigments - if they are technically feasible at all - justifiable from the point of view of ethics and cultural history? To what extent are ageing processes and the associated changes also part of the history of a painting's reception? How can the acceptance of these changes be improved among owners and a broader public?

The subsequent contributions are divided into three sections:

  • Architectural surfaces and church inventory, i.e. topics from the field of architectural and artistic heritage conservation, with the climatic conditions and conditions given by use and the requirements for the appearance of the interior furnishings;
  • Works of art and cultural artefacts in the museum sector, i.e. paintings and objects with polychrome painting that have undergone pigment changes that alter the original artistic statements and can therefore lead to problems in presentation and communication;
  • Prints in archives and libraries, i.e. where climatic conditions are usually very good and use is usually relatively low, combined with the generally widespread acceptance of colour changes.

In four contributions, natural and material scientists, in cooperation with conservators, analyse which pigment is involved and what exactly was the reason and trigger for the pigment change. To do this, they determine the relevant physical, chemical and mineralogical processes, taking into account the historical painting technique, the history of use and conservation and all object-specific conditions.

Hornemann Institute

The final chapter is dedicated to the tasks of the Hornemann Institute and lists its projects, project partners and sponsors over the past 25 years. "I would like to thank all the authors involved as well as the Lower Saxon Ministry of Science and Culture (MWK). Without their support, the conference and the printing of this beautiful book would not have been possible. I would particularly like to thank my colleague Prof Dr Ursula Schädler-Saub. We owe her the inspiration for this topic. The theme was ideally suited to the Hornemann Institute's 25th anniversary celebrations, as the Institute has always strived to promote interdisciplinary research and conservation through conservation science, art history, engineering and the natural sciences. Analogous to the range of topics of the Institute's e-publishing and online courses, as many disciplines of conservation as possible were included in the conference. May the book sensitise many people to pigment changes, far beyond the conservation sciences," says the editor, Dr Angela Weyer, Director of the Hornemann Institute.

The full title of the book

Aus Rot wird Schwarz – und dann? Pigmentveränderungen an Kunst- und Kulturgut,
(Red Becomes Black - and Then What? Pigment Changes on Art and Cultural Heritage)
Proceedings of the interdisciplinary conference of the Hornemann Institute of the HAWK in Hildesheim on the occasion of its 25th anniversary in cooperation with the Conservation/Restoration Work Group of ICOMOS and the Association of Restorers, 9 November 2023, ed. by Angela Weyer and Ursula Schädler-Saub, Berlin 2024
(= Publications of the Hornemann Institute 24)



A. Weyer
Director of the Hornemann Institute
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Profilbild Ursula Schädler-Saub
Grundsätze und Methoden der Restaurierung und der Denkmalpflege, Leitung des DFG-Forschungsprojektes Hyperspektrale Untersuchungsmethoden und die Entwicklung einer digitalen Toolbox für die Erforschung und Vermittlung fragmentarischer Wandmalerei