We have a gingerbread recipe calling for potassium carbonate (vulgo baking potash). One year I replaced the baking potash with baking soda 1:1. It worked fine.

Later I researched what the supposed differences are and found a claim that you may leave the dough up to several days in a cool place to rest when using baking potash but not when using baking soda. The (family) recipe originally also allowed to substitute baking potash for hartshorn salt (ammonium carbonate), but since this has the effect that the dough gets a little runny in the oven and therefore the resulting gingerbread is flatter than desired, we haven't used this in decades.

This answer describes potash as "purely historical leavener". Alas, where I come from (Germany) it is commonly used in Christmas recipes. In fact you will find it alongside the respective spices during the season.

The recipe of my family explicitly allows for storing the ready dough in a cool place for several days. Another recipe of the family of my significant other actually calls for leaving the dough in a cool place for several days and also uses baking potash. I never thought anything of it, but "the internet" appears to ascribe preservative properties of sorts to baking potash.

Or is there something else behind the alleged difference in keeping the dough in a cool place? For example, is baking soda perhaps known to somehow dissolve or otherwise react with the other ingredients and thereby lose its leavening effect?

Could someone please shed some light on the properties baking potash would have in a recipe aside from the leavening effect?! Please provide authoritative sources, if possible.

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    Carbonate is a stronger alkaline than bicarbonate. It'll make the dough tougher and develops stronger gluten. Potassium carbonate is probably the earliest carbonate widely available, before modern chemistry mass produces soda in the early 1900s. Since carbonate doesn't generate gas on its own, you need some acid to react with it, e.g. sour dough, vinegar, lemon juice, sodium aluminium sulfate, etc. "Keep in cool place" is probably the sour dough method. Commented Dec 9, 2019 at 17:53

2 Answers 2


I've never heard of any preservative effect of potash, the reason it is still used in traditional recipes is the ashy flavor it imparts. That smokiness is not to everyone's taste, baking soda is a perfectly good substitute if you prefer the end result.

You can refrigerate baking soda leavened cookie dough for 3-5 days without issue, it's batters where this would be a problem, but it would be whether you used potash or baking soda. The reason is that any chemical leavening agent starts to react with acid right away and produce carbon dioxide. Refrigeration slows this process, but doesn't stop it - cookies don't need as much leavening so it's not an issue whereas for a cake it's a problem.

Refrigerating a spiced dough for a couple of days is a good step because it lets the flavor of the spices come out and blend. You can achieve the same thing by mixing the spices with the butter and refrigerating the butter for a couple of days instead, the end result is the same from a flavor point of view.

  • Thanks, these remarks sound logical. However, do you have authoritative sources backing the claims or is this from your experience or from somewhere else? Commented Dec 9, 2019 at 21:22

Properties baking potash would have in a recipe aside from the leavening effect:

1 tsp of baking soda (NaHCO3) weighs about 4.8 grams. It would require 7.89 grams of potassium carbonate (K2CO3) to provide equivalent leavening power (in terms of volume of CO2 produced). However, since it is "dibasic", it must react with twice as much acid to be fully neutralized, which is how it liberates CO2 gas. To help picture how much acid that is, it takes 68 mL (2.3 fluid oz.) of 5% vinegar to exactly neutralize 4.8 grams of NaHCO3, and it would take - well, twice that much, to neutralize the 7.89 grams of K2CO3. (I recognize that vinegar is not used in most baking recipes.)

A tried and true recipe either has just the right amount amount of acid ingredients to neutralize the leavening agent being used (molasses, for example, is somewhat acidic), or else the taste and effects of the residual unreacted leavening are acceptable.

In addition to the necessary proportion of acid to leavening agent, K2CO3 is significantly more basic when not neutralized - more than 100 times stronger. You would not want to brush your teeth with it. A 0.1 molar solution (about half a tsp in a cup of water) of NaHCO3 would be pH = 8.3 - bitter. An equivalent concentration of K2CO3 would be pH = 10.5 - reasonably corrosive. I mention this to help people consider the effect that the alkali might have on a dough/batter upon storing it, if out of proportion to the acid ingredients.

Hartshorn, or "Baker's ammonia", is (NH4)2CO3. It doesn't require any acid to react, it just breaks down with moisture and heat (to ammonia, water, and CO2). So swapping that into a recipe for one of the carbonates will leave you with more acid in your dough/batter.

Source: a general chemistry book - any one would do.

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