We clean with baking soda, we cook with baking soda, and we bake with baking soda. But baking baking soda? That seems almost counterintuitive.
But if you love the flavor of old-fashioned pretzels and find yourself without (or hesitant to use) lye, which is corrosive and somewhat frightening, bake baking soda you should!
By spreading baking soda out on an aluminum-lined baking sheet and putting it in a 250° F oven for one hour, you'll turn a weak alkali into a stronger one—or, as Harold McGee put it in his 2010 New York Times article outlining the tip, you'll get a "a more muscular and versatile alkali" that's closer in chemical make-up and effect to its hulky cousin, lye (but without as much scariness).
All of this means that, by using baked baking soda, you can get pretzels that are more similar in flavor, color, and chew to the kind that would require you to wear goggles and plastic gloves. (Yes you can make pretzels with straight-from-the-carton baking soda, but McGee says these imposters are actually more like twisted breadsticks. McGee also points out that you should be careful with baked baking soda, too—don't spread it over your forearms.)
To test the tip, I baked Erin McDowell's pretzels using baked baking soda instead of lye. I boiled 10 cups of water with 2/3 cup of baked baking soda, per Alton Brown's ratio, then dipped each proofed pretzel in the bubbling pot, one at a time, for about 30 seconds each. After an egg wash and a salt sprinkle, they were baked as usual.
While my pretzels made with the super-charged baking soda didn't come out quite as dark as Erin's lye-dipped pretzels (see the photos below for a comparison), they did have the distinct, slightly bitter taste of a real live pretzel. And I didn't have to order lye from the internet to make them!
You'll wonder what to do with baked baking soda. You can keep it in a sealed container in the pantry (McGee says indefinitely) to make pretzels to your heart's content, and you can also use it in homemade alkaline noodles—which are chewy, yellow-tinged, and often found in a bowl of ramen.
"One also might detect a vague pretzel-like funkiness in the flavor," writes Michael Laiskonis in Lucky Peach. For both the pretzel maker and the noodle maker, Laiskonis continues, "'baked soda' offers a perfect compromise between weak baking soda and hazardous sodium hydroxide, or lye."
Safety and taste? That's a compromise we can get behind.