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Pure Baking Powder
Two pounds of cream of tartar, one pound bi-carbonate of soda, one pound best flour; sift in sieve four times, put in dry place. If it hardens, put through sieve again.
— Miss Cora White
A four-pound batch of single-acting baking powder, mixed in the classic 2:1:1 proportion. The chemistry is sound and the method needs almost nothing changed, but the powder behaves differently from the tin on the shelf today.
- The ratio is the whole recipeTwo parts cream of tartar to one part bicarbonate of soda by weight is close to the stoichiometric point, though it leaves a slight excess of soda; it is the proportion the cream of tartar powders were built on. Weigh rather than scoop; the two powders differ enough in density that volume measures will throw the balance off.
- What the flour is doingThe pound of flour is a buffer, not a bulking cheat. It separates the acid and base particles and absorbs stray moisture that would otherwise start the reaction in the jar. Cornstarch is used in modern commercial powders for the same purpose and works at the same weight.
- Single-acting, so work fastCream of tartar powder releases nearly all its gas the moment liquid hits it. Batter must go into the oven immediately after mixing, unlike with modern double-acting powder, which holds a second release for oven heat. Do not mix a batter in the morning to bake at night.
- Substituting one for the otherUse it measure for measure where a recipe calls for baking powder, but expect a slightly softer rise in anything that sits before baking. Biscuits, griddle cakes and quick breads suit it best.
- Scale it downFour pounds is a large batch by household standards. At household scale, 4 oz cream of tartar, 2 oz soda and 2 oz cornstarch gives a half-pound jar that will still be fresh when it is finished.
- Sifting four times is not fussinessUneven distribution shows up as bitter yellow spots in a cake crumb where soda has gone unneutralised. Four passes through a fine sieve, or a whisk in a wide bowl, is the minimum for a mixed batch.
- Storage and the hardening problemThe mixture takes up moisture readily, and the caking Miss White anticipates is damp already at work. An airtight jar in a cool cupboard, not above the stove, and re-sift if it clumps. A badly caked batch has probably partly spent itself.
- Test before you trust itA teaspoon in a little hot water should foam vigorously at once. A lazy fizz means the powder has reacted in storage and should be replaced.
Home-mixed baking powder appears constantly in American community cookbooks of the late nineteenth century, and the word pure in the title is doing real work. Commercial baking powders had been sold since the 1850s, and by the 1880s the trade had split into cream of tartar brands and cheaper ones raised with alum, touching off decades of advertising warfare, pamphleteering and state legislation over which was wholesome. Cream of tartar itself was a byproduct of winemaking, scraped as argol from the insides of casks and refined, which made it an import and kept the honest powders dear. Mixing your own from named, single-ingredient chemicals bought at the druggist sidestepped both the price and the argument about what was in the tin, and a housekeeper contributing a four-pound formula to her village book was offering her neighbours some independence from the grocer's shelf.