Egg Washes and Other Glazes

Hi Everyone,

 I've started baking lots of challah and, while I'm really happy with my recipe in general, I realized that I would like to know more about the various washes - egg and otherwise - that can be used in glazing breads and pies. For instance, what are the different effects that come from using just egg yolk, yolk and white, or adding milk or cream? What happens with a water or oil wash? I suppose I could (and will) experiment with all these ingredients and variables, but if anyone has information on washes generally or favorite washes they use in challahs or other breads, I'd like to hear from them.