An additive that increases the plasticity of another material, such as a a cement paste, mortar, or concrete mixture, or the flexibility or softness of organic compounds. Plasticisers are usually non-volatile organic liquids or low-melting solids. Examples are dibutyl phthalate, tricresyl phosphate, ethylene glycol, and castor oil. Phthalate plasticisers were commonly used in the middle of the 20th century for PVAC paints. However, since these oily plasticisers tended to creep and separate with time producing an oily surface and leaving a brittle substrate, later formulations began using copolymerisation techniques for film modification rather than plasticisers. Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis]