The Science of Pie: 7 Pie Crust Myths That Need to Go Away

The Food Lab

Unraveling the mysteries of home cooking through science.

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The science behind pie crust and how to use it to make a better pie. [Photographs: J. Kenji Lopez-Alt]

The world of pie making abounds in myth, legend, tradition, tall tales, short tales, and other manner of never-been-blind-tested theory. And while learning at your grandmother's (or grandfather's) knee may lead you to excellent pie crust—I'm talking all-American, flaky-yet-tender, buttery, rustic pastry here—you're more than likely to pick up a couple of bad habits and un-truths along the way. Today we're going to look at a some of the most common myths in the land of pie crust, poke a few holes in those theories, and hopefully come away with some better recipes in the end. Are you ready?

If you've been following my work through the years at Cook's Illustrated, America's Test Kitchen, and right here at Serious Eats, then you've probably seen my original pie crust recipe or my improved pie crust recipe a number of times. It's a technique I'm particularly proud of, since it produces what I believe to be the most foolproof, easy-to-roll, flakiest, tenderest pie crust around. In honor of March 14th, National Pi Day (get it? 3.14...), I figured now was a good time to give you all a quick recap on exactly how it works and bust a few longstanding pie-making myths in the process.

What Makes Pie Crust Flaky?

Pie crust is essentially made of three ingredients: flour, fat, and water. Everything else (the salt, the sugar, any additional flavors) is just window dressing. It's the seemingly simple interaction between these three ingredients that can make or break a perfect crust.

A classic pie crust is made by cutting a solid fat (generally butter or shortening) into flour until the mixture resembles very coarse meal, then adding in just enough ice cold water to get the mixture to hold together when you squeeze it in your hand. This dough is then formed into a ball, allowed to rest for half an hour or so to fully hydrate and chill, then rolled out. Rolling flattens out and stretches the various regions of fat, flour, and wet flour until it forms many distinct layers.

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If all goes well, after baking you end up with layers of flaky, crisp pastry that have a rich buttery flavor and a tender texture. The sad truth is that more often than not, even at professional bakeries, things don't go so well. I can't tell you the number of pie crusts I've had with leathery, plastic-like, tough, or pasty crusts, but the odds for getting a decent pie when eating out are not good.

To figure out where crusts go wrong, I started by examining the very basics of pie crust, teasing and testing to separate fact from fiction.

Pie Myth #1: Pie Dough Consists of Pockets of Flour Coated in Fat

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The Theory: Old school pastry books will tell you that when you cut butter or some other solid fat (like shortening or lard) into flour, what's happening is that you are encasing pockets of flour inside a shell of fat. Add water and the flour is moistened, whereupon gluten—the network of proteins that lend structure to baked goods—is formed. When you subsequently roll this dough out, these pockets of fat stretch and stretch, eventually forming sheet of fat that separate sheets of gluten-enforced flour. Then, as the pastry bakes, the fatty layers melt, allowing the floury layers to separate from each other, solidify, and form the layers you see in a great pie crust.

The Facts: From the get-go this theory seemed suspect to me. How could the action of cutting a solid fat into a relatively fluid mass of flour possibly cause it to coat pockets of flour in distinct bubbles? And even more importantly, if the fat is really coating these pockets of dry flour, then how would they get moist when you add water to the mix? Wouldn't the fat prevent any water from reaching the flour?

Turns out that pie dough is actually the exact opposite of this: It's not pockets of flour coated in fat, it's pockets of fat coated in flour with a flour/fat paste at the interface. You can clearly see this as a crust is being formed or by slicing into a raw crust, photographing it, and magnifying it to examine how the fat and flour are distributed. More importantly, figuring this out was the first key to improving class pie crust technique, as you'll see.

Pie Myth #2: The Fat Must Stay Clumpy for a Flaky Crust

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The Theory: Clumpy dough means that your fat has not been fully worked into the flour, thus ensuring that layers stay flaky and separate as the bake.

The Facts: While it's true that there must be at least two distinct phases within the pie dough—a water/flour mixture and some form of fat—in order to form flaky layers, it is not true that the fatty layer must be pure fat.

Classic pie crust recipes go through great pains to instruct you to only partially work the fat into the flour in order to maintain pockets of pure fat throughout the dough. This poses a number or problems for the baker. First of all, it's very difficult to gauge exactly how much you should be cutting in your flour. It takes years of practice to get it consistent, and even then slip-ups are not uncommon (hence the bad pies from otherwise great bakeries). For a home baker who makes only a half dozen pies a year, it's even more of a challenge.

The second big problem it causes is that it makes rolling the crust difficult. Pie dough is notoriously tricky to roll, in part because it has big clumps of solid fat in it. These clumps make the dough crumbly and prone to cracking or sticking to the countertop as they melt.

Finally, it affects how much water your dough can absorb. The more you cut your fat into your flour, the less dry flour remains and the less liquid the dough will need to come together. This means that you have to gauge by sight and touch exactly how much water you need for a given batch of pie crust, and that it's likely to be different every single time.

So what's the solution? Well, remember pie dough actually consists of three phases: a water/flour mixture, pure pockets of fat, and a flour/fat paste at the interface between the two. I reasoned that since this flour/fat paste can't absorb any liquid, it's likely that it'll function in a manner very similar to pure fat, with the advantage that it's very malleable and easy to roll.

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Turns out my hunch was correct. For my pie crust recipe, I completely blend fat and flour into a near paste-like consistency, then subsequently very quickly cut some fresh dry flour into it in the food processor. What you end up with is a very consistent ratio of flour/fat paste and dry flour, which means that you can then add the same amount of water, crust after crust. It's a much more consistent (and easy) way to make pie crust.

Pie Myth #3: If The Dough is Easy to Roll, You've Added Too Much Water

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The Theory: Adding extra liquid to your pie dough can help it bind together better, making it less prone to cracking and softer when rolling. However, adding too much water can lead to too much gluten formation, which in turn leads to a leathery or tough crust.

The Facts: Well, this one is true... if you're using a traditional pie crust method. But if you use the flour/fat paste method, your dough will be as supple and easy-to-roll as Play-doh, and it'll come out as flaky and tender as the best pie you've ever eaten.

Pie Myth #4: An All-Butter Crust is Tough to Work With

The Theory: Conventional wisdom states that for a crust with the best flavor, you want to use all butter. But for a crust that's easier to work with and comes out more tender and flaky, you need to cut it with a softer fat like shortening or lard. The idea is that butter is relatively firm when it's chilled, and firm fat means a stiffer dough that's harder to roll out. Shortening and lard are soft even when chilled, which makes for a more pliable dough.

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The Facts: Once again, it all comes down to technique. While it's true that clumps of butter in a traditional pie crust can make rolling it out a pain in the butt, with the flour/fat paste method, you don't have that problem. In fact, my Easy Pie Dough recipe calls for all butter for precisely this reason. All the flavor, none of the difficulty. How's that for win-win?

Pie Myth #5: Acid Will Tenderize Your Crust

The Theory: Gluten formation is inhibited in acidic environments, thus adding vinegar or lemon juice to a pie crust will keep it more tender.

The Fact: Gluten formation is actually improved in mildly acidic environments—down to a pH of around 6 or so. Adding a small amount of acid to a pie crust will make it tougher, not more tender. In order to get any real tenderizing effect, you'd need to add far more acid than a crust can handle, giving it a very sour off-flavor and making it too wet to work with.

Pie Myth #6: Humidity Can Affect Your Crust

The Theory: We've all heard this one: make your pie dough on a humid day and it will absorb moisture from the air, which means you'll have to compensate by adding less water. Or the other version of this myth (a.k.a. the lame excuse method): "I'm sorry my pie crust is so tough! It must have absorbed moisture from the air!"

The Facts: Flour and dough absorb very, very little moisture from the air in the amount of time it takes to make a pie crust. I've tested this numerous times by both storing bowls of flour in dry and humid chambers and making pie crusts in these same chambers. Even at nearly 100% humidity, a pie crust will absorb only a tiny fraction of its weight in water—not enough to make a noticeable difference. It takes weeks or months of storage in a breathable bag in order for flour to really take on a significant amount of moisture. So long as you transfer your flour to a sealed container as soon as you get it home from the supermarket, humidity should have no effect on it at all.

Pie Myth #7: Your Hands or a Food Processor are the Best Tools For Bringing Pie Dough Together

The Theory: Some folks recommend using your hands so that you get a feel for what a good pie dough should be like. Others recommend a food processor as it very rapidly cuts fat into flour and incorporates water, which means less melted fat and a crisper crust.

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The Facts: While a food processor is great for cutting butter into your flour, the best tool for actually forming dough once water has been added is a bowl and a rubber spatula. See, a rubber spatula, with its wide, flat face will start forming flaky layers even before you get to the step of rolling the dough out. This makes for a noticeably flakier crust when finished. To mix with a spatula, dump your butter and flour mixture into a large mixing bowl, sprinkle on your water, then press the dough with the face of the spatula, folding it over itself until it forms a coherent mass.

What About the Vodka?

In my original Cook's illustrated pie dough recipe, I called for a secret ingredients: vodka. Vodka is about 60% water and 40% ethanol, which means that only 60% of it is actually active in aiding gluten development. Meanwhile, 100% of it is active in moistening the dough. By using vodka instead of water, you can add more liquid to your dough, making it easier to roll, while still limiting the gluten development that can threaten to turn your tender dough tough. As the crust bakes, most (but not all!) of the ethanol ends up vaporizing into the air and you're left with a crust that's flaky and tender with no trace of alcoholic flavor.

It's a pretty neat trick and one that has been widely adopted since. Heck, even food science guru Alton Brown has adapted the technique for a pie crust made with applejack. But to be completely honest, it's one that I don't really use at home that often. With the fat/flour all-butter technique, it's really not necessary—the dough is easy to roll out as-is—and in fact, I've even heard some folks complain that the additional liquid that vodka allows you to add makes for a dough that's too sticky to roll out. If you're a pie crust veteran, you'll find it very odd to work with.

There's also the fact that the recipe violates Rule #1 of my home: don't waste alcohol.

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Flaky, flaky layers. Lots of 'em.

That said, if you have a pie crust recipe that you've been using and know inside and out, I'd suggest you try giving it a go replacing the water with 80-proof vodka, brandy, whiskey, or applejack. You may well find that your crust is the flakiest, most tender yet.