Water in Pastry Fats

An important difference between butter and either lard or shortening is that butter is about 15% water by weight, and therefore doesn’t separate dough layers as thoroughly as the pure fats do; water droplets in the fat can glue adjacent layers together. Pastry makers generally prefer European-style butters, which contain less water than standard American butter. However, some water is useful for producing steam that pushes apart the dough layers of laminated pastries. Manufacturers formulate puff-pastry margarine with about 10% water.