A substance that is added to a material to enhance or modify its characteristics, such as curing time, plasticity, colour, or volatility. Additives were used for the preparation of stucco marble. The aim of inorganic additives is to increase hardness, resistance, and durability and to retard setting. They are added at some stage of the working process. The aim of adding organic substances is either to improve the workability, to harden the mass, to retard setting, or to influence the mechanical properties of the stucco mass in a way that it can be polished so that a sufficient gloss is obtained. Wittenburg (1999); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis].