Baking soda is sodium bicarbonate, which already includes one proton and so has a limited ability to take up more. But if you heat baking soda, its molecules react with one another to give off water and carbon dioxide and form solid sodium carbonate, which is proton-free.
- Just spread a layer of soda on a foil-covered baking sheet and bake it at 250 to 300 degrees for an hour. You’ll lose about a third of the soda’s weight in water and carbon dioxide, but you gain a stronger alkali.
- Keep baked soda in a tightly sealed jar to prevent it from absorbing moisture from the air. And avoid touching or spilling it. It’s not lye, but it’s strong enough to irritate.
Baked soda is also strong enough to make a good lye substitute for pretzels. In order to get that distinctive flavor and deep brown color, pretzel makers briefly dunk the shaped pieces of raw dough in a lye solution before baking them. Many home recipes replace the lye with baking soda, but the results taste like breadsticks, not pretzels.
Baked soda does a much better job of approximating true lye-dipped pretzels. Just dissolve 2/3 cup (about 100 grams) in 2 cups of water, immerse the formed raw pretzels in this solution for three to four minutes, rinse off the excess dipping solution in a large bowl of plain water, and bake.