Baking Powder
8 ounces bicarbonate of soda 6 ounces tartaric acid 1 pound high-grade cornstarch Put all the ingredients together and sift them thoroughly five times. Keep closely covered in glass jars or tin boxes.
A single-acting home baking powder, made by weight. It works, but it behaves differently from the double-acting tin on the supermarket shelf, and that difference governs how you use it.
- It is single-actingTartaric acid dissolves and reacts almost instantly on contact with moisture. Batters made with this powder must go into the oven the moment they are mixed; standing on the counter for ten minutes will cost most of the lift.
- Weigh, do not scoopThe proportions are given in ounces by weight and the three powders have very different densities. Converting to spoons will throw the balance out. Use a scale: 8 oz (225 g) soda, 6 oz (170 g) tartaric acid, 1 lb (450 g) cornstarch.
- The soda is slightly in excessSix ounces of tartaric acid will neutralise only about six and three-quarter ounces of bicarbonate, not eight. Expect a faintly soapy, alkaline note in delicate white cakes. Taking the soda down to about 6 3/4 oz, or the acid up to about 7 oz, brings it closer to neutral.
- Tartaric acid, not cream of tartarThese are not interchangeable. Cream of tartar is potassium bitartrate and is roughly 40 per cent as acidic by weight; a substitution would need something like two and a half times the quantity and would still act faster than a commercial powder.
- Why the cornstarchIt is not filler for its own sake. The starch keeps the two reactive powders physically separated and absorbs stray moisture, which is the reason for the tightly closed jar; the five siftings distribute the three powders evenly through one another.
- Storage and testingDamp air is the enemy, and a humid kitchen will shorten the working life of a jar considerably. Test by dropping half a teaspoon into hot water; it should fizz hard and immediately.
- Yield and useThe recipe makes about 30 oz, near two pounds of powder. Reckon on 1 to 1 1/4 teaspoons per cup of flour.
Home-mixed baking powder appears in household books of this period for two reasons: economy, and suspicion. Chemical leavening spread rapidly through American kitchens after the middle of the nineteenth century, and by the 1880s and 1890s rival manufacturers were waging a long public argument, generally remembered as the baking powder wars, over whether alum-based powders were wholesome. Cream of tartar brands advertised their purity, alum brands their price, and legislatures in several states were drawn into the fight. Against that background a formula the cook could mix and measure herself was making a quiet point about knowing exactly what went into the cake.