Egg wash VS milk wash
When baking bread, pie and other pastries, some recipes call for an egg wash, others for brushing the top with milk. What are the differences in the finished baked good? Is there any other 'washes' used that I'm not aware of? If one ingredient is not available, can you substitute another wash in it's place?
Egg washes work well on pie crusts or loaves of bread where you want some sheen and nice browning. Picture the shiny golden crispy coating on a baguette or loaf of French bread.
Milk (or cream) washes aid with browning but aren't so shiny. They're good on things like scones.
The other benefit of a wash before baking is it will help toppings to adhere, like a sprinkle of coarse sugar on pie or scones, or flaky salt on biscuits or dinner rolls.
Other types of washes I use regularly are just things like butter or olive oil on top of dinner rolls or pizza crust.
Yes, you can substitute one wash for another but you will see a difference in the finished product. I will try and dig up some photos to show you.
There is a book that depicts various washes and how they look after baking. It's in the book "Ultimate Bread" by Eric Treuille and Ursula Ferrigno page 59.