The different proportions of cobalt phosphate-containing nano-crystallite composite paints have been synthesized with CaCO3 and polyvinyl acetate adhesive. The abbreviations of these composite paints are CPM2, 2.50% Co3(PO4)2, CPM4, 4.49% Co3(PO4)2, and CPM6, 6.52% Co3(PO4)2. The specific heat capacity (Cp) of all these composite paints is found endothermic. The optimum value of Cp is observed for CPM2 composite paint among all paints. At 298 K, Cp of composite paints are 1.00 J g−1 K−1 for CPM2, 0.88 J g−1 K−1 for CPM4, and 0.81 J g−1 K−1 for CPM6. The Cp of Co3(PO4)2 is 0.94 J g−1 K−1 at 298 K. The ∼ 80% reflectance of polyvinyl acetate containing CaCO3 paint is reduced to ∼ 30% with the addition of 6.52% Co3(PO4)2. The composite paints are found semiconducting behavior due to band gap Eg 2.15 eV at λmax = 576 nm. The crystallite size of the CPM6 composite paint is 59.64 nm.