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Plasticine, a brand of modelling clay, is a putty-like modelling material made from calcium salts, petroleum jelly and aliphatic acids. The name is a registered trademark of Flair Leisure Products plc. Plasticine is used extensively for children's play, but also as a modelling medium for more formal or permanent structures. History Plasticine was formulated by art teacher William Harbutt of Bathampton, in Bath, England, in 1897. He wanted a non-drying clay for his sculpture students...

The sky is the part of the atmosphere or outer space visible from the surface of any astronomical object. It is difficult to define precisely for several reasons. During daylight, the sky of Earth has the appearance of a pale blue surface because the air scatters the sunlight. The sky is sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars...