Baking ammonia is a chemical leavening agent, ammonium bicarbonate, that produces an exceptionally light and crispy texture in cookies, crackers, and other thin baked goods. It predates both baking soda and baking powder by centuries and remains a staple in traditional European baking. While it sounds unusual, it’s a straightforward ingredient with a specific purpose: creating airy, porous crumb that other leaveners can’t quite replicate.
What Baking Ammonia Actually Is
Baking ammonia is the common kitchen name for ammonium bicarbonate (NH₄HCO₃). You’ll also see it labeled as “hartshorn salt,” “baker’s ammonia,” or simply “ammonium.” It’s a white, crystalline powder with a faint ammonia smell that becomes much stronger when heated. In Scandinavian and German baking traditions, it never fell out of use, even after baking powder became widely available in the mid-1800s.
The name “hartshorn” comes from its original source material. Before it was manufactured synthetically, ammonium bicarbonate was produced by grinding up the antlers of a hart (a male deer). It could also be obtained by distilling hair or decomposed urine. These methods were common through the 1700s, though antlers were initially used more for making gelatin than for leavening. It wasn’t until the late 1700s that bakers began using hartshorn as a rising agent. Today, it’s produced industrially and sold in small containers at specialty grocery stores and online.
How It Works as a Leavener
When baking ammonia heats above about 40°C (104°F), it breaks down completely into three components: ammonia gas, carbon dioxide, and water vapor. All three contribute to leavening by expanding inside the dough, pushing cell walls apart and creating a porous, tender structure. This triple action is what gives baking ammonia its distinctive lift.
The key difference from baking soda or baking powder is that baking ammonia leaves absolutely no chemical residue behind. Baking soda decomposes into alkaline sodium carbonate, which stays in the finished product and can leave a slightly soapy or metallic taste if you use too much. Baking ammonia, by contrast, converts entirely into gases that escape during baking. This means it has virtually no effect on the pH of the finished product, which also slightly reduces surface browning compared to baking soda.
There’s one important catch: the ammonia gas needs to fully escape from the baked good, or it will leave an unpleasant smell and taste. This is why baking ammonia works best in thin, flat items like cookies, crackers, and wafers. In a thick cake or bread loaf, the ammonia gas gets trapped inside, and the result is inedible. Stick to recipes where the dough spreads thin or is rolled flat before baking.
What It Does to Texture
Bakers reach for ammonium bicarbonate specifically because of the texture it creates. Cookies made with baking ammonia come out noticeably crispier and more porous than those made with baking powder or baking soda. The gases expand the cell walls of the dough during baking, producing a finer, more uniform crumb with a satisfying snap. Think of the dry, airy crunch of a traditional German Lebkuchen or the delicate bite of a Springerle cookie.
Beyond crispiness, baking ammonia also tenderizes. The rapid gas expansion stretches the cell walls thinner, so the finished product feels light rather than dense. This combination of crisp and tender is difficult to achieve with other leaveners alone, which is why many traditional recipes specifically call for it rather than offering substitutions.
Traditional Recipes That Use It
Baking ammonia shows up most often in Northern European holiday baking. German Springerle cookies, those elaborately stamped anise-flavored biscuits, traditionally rely on either baking ammonia or potash (potassium carbonate) for their characteristic texture. Lebkuchen, Honigkuchen, and a German pastry called Amerikaner all use it to “loosen” the crumb without adding the alkaline taste that baking soda would introduce.
Scandinavian baking uses it heavily in thin, crisp cookies. If you’ve ever had a traditional Swedish dream cookie (drömmar) with that impossibly light, crumbly texture, baking ammonia is the reason. It’s also common in Greek koulourakia and certain Middle Eastern flatbreads and crackers where extreme crispness is the goal.
Storage and Shelf Life
Because baking ammonia begins to decompose at relatively low temperatures and releases gas even at room temperature (slowly), proper storage matters more than it does for baking soda or powder. Keep it in a tightly sealed, airtight container in a cool spot. If the container isn’t sealed well, the ammonia gas gradually escapes, and the powder loses its leavening power over time.
To check whether your baking ammonia is still potent, open the container and smell it. Fresh ammonium bicarbonate has a sharp, unmistakable ammonia odor. If it smells like nothing, it has already decomposed and won’t do anything in your recipe. You can also drop a pinch into a small amount of warm water. Active baking ammonia will fizz as it releases carbon dioxide.
Substitutions
If you can’t find baking ammonia, the standard substitution is a 1:1 replacement with baking powder. For some recipes, particularly those that benefit from extra lift, you can use equal parts baking powder and baking soda combined to replace the same amount of baking ammonia. So if a recipe calls for one teaspoon of baking ammonia, use one teaspoon of baking powder, or half a teaspoon each of baking powder and baking soda.
Keep in mind that substitutions change the final texture. You’ll get a reasonable rise, but the distinctive ultra-crisp, porous quality that baking ammonia produces won’t be the same. Baking soda also raises the pH of the dough, which increases browning, so your cookies may come out darker than intended. For recipes where the texture is the whole point, like Springerle, it’s worth tracking down the real thing at a European grocery, specialty baking shop, or online retailer.