Pastry bag

A pastry bag (or piping bag in the Commonwealth) is an often cone- or triangular-shaped, hand-held bag made from cloth, paper, or plastic that is used to pipe semi-solid foods by pressing them through a narrow opening at one end, for many purposes including cake decoration. It is filled through a wider opening at the opposite end, rolled or twisted closed, and then squeezed to extrude its contents.

Though a circular nozzle is quite useful for making round shapes and for filling pastries such as profiteroles, many differently shaped nozzles are commonly used to produce star, leaf, and flower-petal shapes.

Aside from icing, pastry bags are commonly used to shape meringue and whipped cream, and to fill doughnuts with jelly or custard. They are used to form cream puffs, éclairs, and ladyfingers. When presentation is especially important, fluted tips can be used to shape savory foods such as filling for deviled eggs, whipped butter, and mashed potatoes (especially for Pommes duchesse).

A high-quality reusable bag is often made from tightly woven nylon, polyester, rubber or waterproofed (plastic-coated) cotton. Medium quality bags are similar, except they are not so tightly woven and may let some contents seep through the weave or the seams. After use, a reusable bag is washed by hand and hung open to dry. A high-quality bag may last for many years.

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Wikipedia