Just before sliding puff pastry, pâte à choux, a double-crusted pie, or a loaf of bread into the oven, most bakers brush the top of the pastry with an egg wash. The term egg wash simply means an egg, or a part of an egg, that has been thinned with a bit of water, milk, or cream and is used to promote browning or to create a glossy shine, or both. How brown or shiny the crust becomes depends on the makeup of the egg wash (see the chart, below).
The protein and fat in an egg cause different effects. Protein promotes browning, while the fat in the yolk gives crusts a nice shine. Since there is protein in both the yolk and the white, any whole egg or yolk will make the crust both shiny and brown. The white, on the other hand, will only promote browning without contributing any significant gloss to the crust.
Egg washes may contain water, milk, or cream, and sometimes salt. Since the best-looking pastries are made by applying a thin, even coat of egg wash, adding a little liquid (1 tablespoon per egg, or 1/2 tablespoon per yolk or white) will help thin it and make it easier to brush.
Besides diluting the egg, milk or cream will also affect the final appearance. Since milk is mostly protein, it will increase the browning when added to an egg yolk. Milk has little effect when added to whites or whole eggs since the protein content is already relatively high. Cream, on the other hand will increase the gloss of the crust because of its high fat content.
Some chefs like to add salt (a scant 1/8 tsp. per egg) to an egg wash because it breaks down the proteins and thins the white, making it easier to brush on. Keep in mind that you must wait a minute or two for the salt to become effective.
The best tool for applying an egg wash is a natural bristle pastry brush. Keep it clean by washing it immediately after use; don’t let egg dry in the bristles. When applying an egg wash to puff pastry or other flaky dough that’s meant to rise in the oven, be careful not to let the glaze run over the sides or it will, in effect, glue the flaky layers together and prevent them from rising.
Likewise, if you’re planning to score the surface of a loaf of bread or pastry, first brush on the egg wash, and then score the dough so the egg wash doesn’t drip into the score marks and seal them closed.
Customize egg washes for varied effects
Content of egg wash
Effect on cooked pastry
|whole egg with water
||nicely browned, slightly glossy
|whole egg with milk
||nicely browned, more glossy
|egg white only
||evenly browned, slightly less brown than whole egg, very little shine
|egg yolk only or egg yolk with water
||browned and shiny, but less so than with cream or milk
|egg yolk with cream
||very browned and glossy, but a relatively thick egg wash that's somewhat difficult to spread neatly
|egg yolk with milk
||the darkest brown crust and a touch less shiny than yolk with cream