Q: What does the term "blind baking" refer to?

When making pastries, tarts, flans, quiches or other items with a crust, it is sometimes necessary to bake the shell before the filling is put in.  This helps prevent the filling from making the crust soggy or keeping it from cooking completely.  It also allows you to cook the crust at a higher temperature in order to have it turn out light and flaky and then cook the filling at a lower temperature so that it doesn't overcook.  This is particularly useful for custard pies (see "Custards and Sauces").

When blind baking a pie shell, the pastry is rolled out, put into the pie pan and shaped or trimmed as called for in the recipe.  The bottom of the shell is pierced all over its surface using a fork or a special tool called a docker, which looks like a spiny roller, to keep the crust from puffing too high.

The pastry is then lined with parchment paper or lightly oiled aluminum foil and filled with some sort of  weight, such as dried beans, rice, or weights specifically made for the purpose.  It is baked in a hot oven, usually around 400°F (205°C) for about 10 minutes, after which the parchment or foil is removed, along with the weights, and the bottom is cooked for another 5 minutes or so, until light brown.  If necessary, the edge of the crust may be shielded with strips of foil to keep it from over cooking.

After this, the shell may be lightly glazed with an egg wash, or lightly beaten egg white,  and baked for a few more minutes to cook the glaze.  This step is optional, but may help to keep the crust from getting soggy.

Once the crust has cooled to room temperature, it may be filled with whatever filling is desired, and baked  following the appropriate recipe.