Tin cry Tin cry A tin cry is the characteristic sound heard when a bar of tin is bent. Variously described as a "screaming" or "crackling" sound, the effect is caused by the crystal twinning in the metal. The sound is not particularly loud, despite terms like "crying" and "screaming". It is very noticeable when a hot-dip tin coated sheet metal is bent at high speed over rollers during processing. The tin cry is often demonstrated as a simple science experiment. The bar of tin will "cry" repeatedly when bent until it breaks. The experiment can then be recycled by melting and
Gift economy Gift economy A gift economy, gift culture, or gift exchange is a mode of exchange where valuables are not traded or sold, but rather given without an explicit agreement for immediate or future rewards. This exchange contrasts with a barter economy or a market economy, where goods and services are primarily exchanged for value received. Social norms and custom govern gift exchange. Gifts are not given in an explicit exchange of goods or services for money or some other commodity. The nature of gift economies forms the subject of a foundational debate in anthropology. Anthropological research into gift economies began