I wanted to put this where I could lose it and possibly find it again using search for Glazing or Primer
Here is the Rose Levy Beranbaum’s take on brushing on a crust
Type of Glazes and Toppings
A crisp crust: Water (brushed or spritzed)
A powdery, rustic chewy crust: Flour (dusted)
A soft velvety crust: Melted butter, preferably clarified (1/2 tablespoon per average loaf)
A crisp light brown crust: 1 egg white (2 tablespoons) and 1/2 teaspoon water, lightly beaten and strained (the ideal sticky glaze for attaching seeds)
A medium shiny golden crust: 2 tablespoons egg (lightly beaten to measure) and 1 teaspoon water, lightly beaten
A shiny deep golden brown crust: 1 egg yolk (1 tablespoon) and 1 teaspoon heavy
cream, lightly beaten
A shiny medium golden brown crust: 1 egg yolk (1 tablespoon) and 1 teaspoon milk, lightly beaten
A very shiny hard crust: 1 1/2 teaspoons cornstarch and 6 tablespoons water: whisk the cornstarch with 2 tablespoons of the water. Bring the remaining 1/4 cup
water to a boil and whisk the cornstarch mixture into it; simmer for about 30 seconds,
or until thickened and translucent. Cool to room temperature, then brush on the bread
before baking and again as soon as it comes out of the oven.
Note: When using an egg glaze, it goes on most smoothly if strained. I like to add a pinch of salt to make it more liquid and easier to pass through the strainer. An egg glaze will lose its shine if using steam during the baking process. My preference is to use Safest Choice pasteurized eggs.