From ancient plaster to modern sustainability: assessing starch granules and organic components in historical earthen plasters for environmental applications

This study investigates the starch composition of ancient earthen plasters from western India’s Buddhist caves in Karla, Bhaja, Ellora, Aurangabad, and Pitalkhora, employing a comprehensive methodology that integrates microscopy, image processing, and FTIR spectroscopy. Through polarized and normal light microscopy, starch grains from wheat, millet, mung beans, and rice were identified and characterized. Geometric properties of these granules—such as area, perimeter, and roundness—were measured using ImageJ software, with classification accuracy enhanced by a discriminant formula developed through Statistical Package for the Social Sciences (SPSS 26), a software tool widely used for statistical analysis. Notable findings include millet being the dominant starch in Pitalkhora plaster and rice starch present across all cave plaster samples, though in varying concentrations: Bhaja (31%), Ellora (26%), Karla (14%), Pitalkhora (14%), and Aurangabad (7%). Millet starch concentrations were highest in Pitalkhora (51%) and lowest in Ellora (11%). FTIR analysis of water-extracted samples revealed starch, gums, and proteinaceous additives, confirming diverse organic components in the plaster. This research elucidates regional variations in plaster compositions and highlights the advanced knowledge and skill in material selection and application in ancient construction practices. The study bridges past and present by demonstrating how the strategic use of plant-derived additives in ancient plasters can inspire innovative, eco-conscious solutions in contemporary building practices, underscoring the relevance of traditional knowledge in addressing today’s environmental challenges.