Evaluation of Cow Bone Ash as a Partial Replacement for Calcium Carbonate in Ceramic Glaze Formulations in Kaduna State

This study evaluates cow bone ash as a partial replacement for calcium carbonate in ceramic glaze formulations, using locally sourced materials from the Kaduna abattoir system, North West Nigeria. The ceramic industry in Kaduna and its environs generates significant demand for glaze raw materials, most of which are imported, while cow bone waste from abattoirs presents a largely unutilised calcium-rich secondary resource. Cow bones are collected, degreased, calcined at 900 degrees Celsius, and characterised for chemical composition and particle morphology using XRF and SEM. Bone ash is incorporated into a standard transparent glaze batch as a replacement for calcium carbonate at 0, 25, 50, 75, and 100 percent substitution levels. Glazed ceramic tiles are fired at 1100 and 1150 degrees Celsius, and the resultant surfaces are evaluated for surface texture, gloss, colour, thermal expansion, and scratch resistance. Results indicate that up to 50 percent bone ash substitution produces glazes with comparable gloss and surface quality to the control, attributed to the hydroxyapatite phase contributing to glassy network formation. Higher substitution levels produce milky, opaque surfaces due to undissolved calcium phosphate phases at 1100 degrees Celsius firing temperature. Scratch resistance improves marginally with bone ash addition. The study recommends 25 to 50 percent bone ash substitution as technically viable for use in local ceramic production. Keywords: cow bone ash, ceramic glaze, calcium carbonate, calcination, Kaduna State.