Tip: Egg Wash #1: Pie and Tart Crust

In DEFINITION: Egg Wash, I described egg washes in general.

What are they good for besides just making something shiny?

Well, if you ever have a problem with soggy crusts in pies or tarts, you can use an egg wash to prevent that. When baking pies or tarts, brush the inside bottom of the cooked pie shell with the white of an egg. This will insure a dry under crust.

DEFINITION: Egg Wash

An egg wash is a coating applied to some baked goods and other foods to create a distinctive finish. Especially in the field of baking, an egg wash is often added to breads and sweets to create a glazed look. Egg brushed bread will also have a slightly more crispy, flaky crust, which is sometimes a desired texture in baking. As one can imagine, there are several different types of egg wash, all of which have a different end impact on the food.

A very basic egg wash is made by simply lightly beating an egg and brushing it onto the food. Other ingredients such as milk, water, or salt may be added for a specific finish, and eggs are also frequently separated to make an egg wash. Some recipes specify which type of egg wash should be used, while others allow the cook to decide which would be best. In any case, the eggs used in an egg wash should be as fresh as possible.

More here:
http://www.wisegeek.com/what-is-an-egg-wash.htm