‘Keim'sche Mineralfarben’ marker: Is it a myth? A comprehensive analytical study of its detection methods and true nature

This study addresses the challenge of identifying Keim'sche Mineralfarben by developing a refined analytical protocol that compares the 1920s–1930s samples with silicate paint products from the same period. In response to the long-standing question, “Keim or not Keim?” we re-evaluate the potential of CaF₂ as a marker for Keim'sche Mineralfarben through the analysis of authentic colour charts. The findings show that CaF₂ alone is an inadequate distinguishing feature. Instead, a reliable identification requires considering multiple key characteristics. We introduce a novel set of analytical fingerprints for differentiating Keim'sche Mineralfarben from other silicate paints. By combining laboratory analysis with archival research, this integrated approach aims to confirm the presence of Keim'sche Mineralfarben, assess the effectiveness of current methods for this purpose, and clarify their limitations. These results highlight the need for advanced analytical investigations to authenticate Keim'sche Mineralfarben and identify their unique chemical properties. • CaF₂ alone is insufficient for identifying Keim'sche Mineralfarben; a combination of chemical features is essential. • Key additives such as ZnO, Al(OH)₃, and BaCO₃ distinguish Keim'sche Mineralfarben from others. • SEM-EDX proves superior for analyzing historical silicate paints over other analytical techniques. • Combining archival research and lab analysis reveals new insights into Keim'sche Mineralfarben. • The applicability of the suggested protocol on weathered façade paints remains an open question for further study.