A piping bag, or pastry bag
is a receptacle that holds pastry stuff like, choux paste
, bavarian cream
, or even plain old cake icing
that is to be applied to any piece of pastry.
It can be made out of waterproofed cloth or disposable food grade polyethylene, i.e. plastic, and can be fitted with different nozzles to make different shapes out of the pastry material inside. The nozzles for example can be star shaped or just a plain hole but the motion that the patissier makes while piping will also determine what the product will look like if one is making pastries. There also are special nozzles which are used to inject sweets or creams into pastries to give it a filling.
The piping bag is used to make writings on cake for example and is an indispensable tool for any patissier who makes delicate pastries or anything that is not just plain bread but rather more fancy.