An egg wash is usually beaten eggs

Egg (food)

Eggs are laid by females of many different species, including birds, reptiles, amphibians, and fish, and have probably been eaten by mankind for millennia. Bird and reptile eggs consist of a protective eggshell, albumen , and vitellus , contained within various thin membranes...

 sometimes mixed with another liquid, usually water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 or milk

Milk

Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

, which is brushed onto the surface of a pastry before baking. An egg wash is often used to make pastries shiny and golden or brown in color, and it also is used to help toppings or coatings stick to the surface of the pastry, or to bind pastry parts together. The part of the egg used and liquid added determines the finished look of the crust.

Vegan substitutes for egg wash include vegetable oil, non-dairy milk and butter substitutes, and light corn syrup

Corn syrup

Corn syrup is a food syrup, which is made from the starch of maize and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor...

 thinned with water. Egg washes can also be used on calzoni

Calzone

A calzone Italian: , "stocking" or "trouser") is a turnover that originates from Italy. It is shaped like a semicircle, made of dough folded over and filled with ingredients common to pizza....

 or on fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

.