If you or someone you know is into old (actually very old) recipes, odds are you’ve seen this listed as an ingredient here and there. Pearlash is refined potassium carbonate, an alkaline salt found in wood ashes that also goes by the name potash. Potash was used for a lot of things back in the 1700s and 1800s, especially glassmaking. These days we mostly know it as a fertilizer, but once upon a time it was used to leaven things like corn cakes since it makes bubbles when it gets wet. Given that potash was made from wood ash, its effect on the flavor of corn cakes was as you might expect, but hey, at least the texture was lighter.

The problem was partly solved by a chemist named Antonio Campanella who, in 1745, invented a way to refine potassium carbonate by heating it and burning away more of the ashen residues. That got rid of enough of the burnt wood flavor to make it an acceptable leavener many American home bakers. The first printed recipes containing pearlash appeared in 1796. If you’re in possession of a recipe dating to that time, just substitute baking soda but use about half again as much.

2 thoughts on “Pearlash”

  1. Hi Joe,

    I just wanted to mention lest readers get the wrong impression that potash and hirschhorn are still used in German baking. It’s true that the recipes are old, but they are still in use, and specialty stores with a European clientele continue to carry at least one or the other. I’ve been able to find potash in mid-sized cities in both Canada and the UK, in the foodie shops that also sell imported German cookies at Christmas.

    One thing to be aware of is that once potash sits around with any moisture in it, it gets a very foul smell and taste, so unless the package is kept very tightly sealed, it’s difficult to use from one year to the next – and that’s an aggravation since personally I only use it in Christmas baking, in minuscule quantities.

    Functionally, you’re probably right that baking soda will do the job. However, my recipes with potash have a distinct but not easily described taste (not a bad one!) that baking soda doesn’t replicate. That’s once it’s baked, though. Raw batter made with potash is not entirely pleasant 🙂

    1. Very interesting, Jen! I know some bakers who still use hartshorn (baker’s ammonia) but I didn’t know potash was still in use and available anywhere. Thanks for a great comment!


      – Joe

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