The most commonly used chemical in wall putty is calcium carbonate (CaCO3). Calcium carbonate is a white powder that is used to fill in cracks and holes in walls, and to give them a smooth finish. It is also used to increase the strength of the wall and to reduce the absorption of moisture. Other chemicals that may be used in wall putty include talc, silica, and gypsum. These chemicals are used to improve the adhesion of the putty to the wall, and to reduce the shrinkage of the putty when it dries.