<P> A widget is a device placed in a container of beer to manage the characteristics of the beer's head . The original widget was patented in Ireland by Guinness . The "floating widget" is found in cans of beer as a hollow plastic sphere, approximately 3 cm in diameter (similar in appearance to table tennis ball, but smaller) with at least one small hole and a seam . The "rocket widget" is found in bottles, 7 cm in length with the small hole at the bottom . </P> <P> Draught Guinness, as it is known today, was first produced in 1964 . With Guinness keen to produce draught beer packaged for consumers to drink at home, Bottled Draught Guinness was formulated in 1978 and launched into the Irish market in 1979 . It was never actively marketed internationally as it required an "initiator" device, which looked rather like a syringe, to make it work . </P> <P> Some canned beers are pressurized by adding liquid nitrogen, which vaporises and expands in volume after the can is sealed, forcing gas and beer into the widget's hollow interior through a tiny hole--the less beer the better for subsequent head quality . In addition, some nitrogen dissolves in the beer which also contains dissolved carbon dioxide . Oxygen is generally excluded as its presence can cause flavour deterioration . </P> <P> The presence of dissolved nitrogen allows smaller bubbles to be formed, which increases the creaminess of the head . This is because the smaller bubbles need a higher internal pressure to balance the greater surface tension, which is inversely proportional to the radius of the bubbles . Achieving this higher pressure would not be possible with just dissolved carbon dioxide, as the greater solubility of this gas compared to nitrogen would create an unacceptably large head . </P>

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