Although it is a registered brand name, Plasticine (like Sellotape and Hoover), has become synonymous with its product – in this case modelling clay. Modelling materials of this type are malleable and non-drying putty-like substances made from a mix of calcium salts, petroleum jelly and aliphatic acids. Popular with children and artists, it is used for creative play, structures, artwork (such as stop-motion animation) and commercially (as moulds for plastics). The branded Plasticine was originally formulated by English art teacher William Harbutt who wanted a re-mouldable clay for his students – it went into production commercially in 1900. Originally grey, four colours were produced for consumers and more colours followed. The formula was amended in 1915 – lambs wool or cotton wool was added; this gave a stronger more fibrous mixture which was better suited to use as ear plugs and as a sterile dressing.