development of a natural surface coating for clay-based surfaces based on historical practices

Clay has been one of the earliest and most versatile building materials, essential for bricks and as a binder for plaster on earthen walls. despite advancements in surface coatings, there is limited research on coatings specifically for clay-based surfaces. this study addresses this gap by developing a novel clay coating inspired by ancient sri lankan techniques. key ingredients include pine gum, haldummala (shorea oblongifolia), dorana (dipterocarpus glandulosus) oil, and ethanol. fifteen samples with varying haldummala concentrations (2-10 g in 2 g increments) were tested. sample 2, with 4 g/l of haldummala, showed superior properties: a density of 0.9529 kg/l, 55.48 % solid content, 21 seconds viscosity, 10.48 % opacity, and 33.5 gloss units at 60 °. no peeling, cracking, or blistering occurred after 500 hours of artificial aging in quv tests. both natural and commercial coatings showed similar gloss reductions (9-12 %) but retained over 80 % of their initial gloss, demonstrating strong uv resistance. the natural coating also achieved a permissible voc content of 3.5 lb/gal. the carbon footprint analysis revealed that the natural coating emitted 1210 kg co₂-equivalent, 61.9 % lower than the 3180 kg co₂-equivalent of its commercial counterpart. this significant reduction highlights its environmental sustainability. overall, the new formulation proved to be a durable, eco-friendly, and effective coating for clay-based surfaces, offering a viable alternative to conventional options.