“Sift ingredients together” is a lot like “read instructions before assembly.” It's a direction most people completely ignore, then complain when whatever they were making doesn’t turn out right. Why are we so averse to such a simple step? Probably because it’s common belief a special piece of equipment called “a sifter” is required: a metal cylinder with a mesh screen and a little hand crank that you spin like an organ grinder—an activity that seems will do little more than make you wish you had a monkey. It’s also hard to motivate yourself to dig through your cabinets to find a tool that’s probably buried somewhere in the back with the rest of the stuff you never use, especially when you know you’ll be using it for ten seconds.
No one blames you for this line of rationalization, because you’re right—it’s stupid. That’s why you should use the wire mesh strainer that you use several times a week, because it’s right in front of you and dishwasher safe. Put your dry ingredients in, give it a little shakity-shake, and that’s all she wrote. You can now toss that sifter and free up precious cabinet space to fill up with novelty hot sauces.
But even though we’ve solved the equipment hurdle, why should you even bother taking the extra step when you’ve gone so long without doing it? Because it’s going to stop your baked goods from sucking. And the origin of nearly all suckitude is flour clumps, the very enemy sifting is built to destroy.
There are two ways clumps happen. One, they’re already present in the flour when you scoop it from the bag. Two, they naturally occur when the flour gets wet. If you can remember back to your second grade paper mache days, mixing flour and water together makes paste. The moment a speck of flour hits liquid, it sucks it up and becomes a pasty globule desperate for a friend, reaching out to find one of its siblings to hold onto. In the first scenario, all the flour on the outside of that clump will bond together and make a starch balloon, leaving all the flour trapped inside completely raw. Contrary to popular belief, this won’t magically remedy itself in the oven. When you cut open your cake or muffin, you’ll have little balls of raw flour in there, which aren’t nearly as good as chocolate chips or blueberries.
In the second scenario, if your dry ingredients are not well mixed beforehand, you’ll end up with a pool of flavored paste. If things like sugar, salt and leaveners are evenly sifted in, they’ll act as a security team, preventing the starchy globules from rubbing up on each other and making clump babies.
How do both these scenarios lead directly to terrible baked goods? The number one reason for baking failure is overworking your batter. The longer you stir, the more gluten forms, resulting in gummy muffins and cakes. You want to mix your batters as little as you possibly can, just until everything comes together. If you’re using an electric mixer, that literally means seconds, not minutes. When clumps are present, you’ll want to get them out, and the only way to do this is to mix on and on and on until they all break up. Or, you can take the ten seconds and sift. That would be much smarter.