Chemistry is the magical force that makes flour and water become dough instead of turning into a cloudy liquid. Gluten proteins in wheat flour don't dissolve in water because they form molecular bonds with it. In the presence of water, gluten proteins change shape and gain the elasticity characteristic of dough. Starch, which makes up 70 percent of the weight of flour, also grabs water to form chemical bonds. Starch bond networks weave themselves through gluten networks to tenderize the dough and hold its shape during and after baking.
If you want wafer-thin, flaky dough for one dish and sturdy, hardworking dough for a different dish, all you have to do is alter the way the chemical bonds form. Fats, such as lard, butter, shortening, oil, cream cheese and sour cream, are what differentiate pastry dough from pasta or bread dough. Fats work to break up gluten and starch networks. They literally shorten the bonds formed between flour and water, hence the term "shortening." The shortened bonds have a weaker chemical structure, making the dough more tender. Before baking, the flaky layers of piecrust and puff pastry actually float on microscopic layers of fat.
The type of flour you use and your technique in working the dough influence the finished product, too. Flour specifically for pastry is milled from soft red wheat. This wheat has less protein than other flours, so it will form weaker gluten networks when mixed with water. The temperature of that water is important for your dough's success and varies depending on what type of dough you make. Liquids are nearly boiling for cream puff pastry but ice cold for pie and tart crusts.
Shortening yields a lighter pastry than butter, but butter pastries have better flavor. Always use unsalted butter so you don't overdo the salt content and turn out tough dough. Fats such as cream cheese and sour cream make rich, moist dough.
Overworked dough crumbles instead of flaking. Underworked dough may be tough because the fat isn't dispersed evenly. Cooking at too-low temperatures melts fat out of the molecular bonds rather than boiling it in to create a delicate, flaky finished pastry.
Now that you know what makes dough work, learn how it's been employed through the ages.