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Egg-Powder
Egg-powder, as it is called, is a compound intended to serve as a substitute for eggs, to four of which one penny packet professes to be equivalent in cake making, and sufficient to add to two pounds of flour. It is commonly made as follows. Take one pound of cream of tartar, half a pound of bicarbonate of soda, two ounces of powdered magnesia, one ounce of powdered carbonate of ammonia. Mix thoroughly, and keep in a dry place.
This is a formula rather than a dish: a bulk chemical leavener sold in penny packets as an "egg substitute" for plain cakes. It works on the same principle as modern baking powder, and the proportions are still legible to anyone who understands that.
- What it actually isThe name is marketing. Nothing here replaces the protein, fat or emulsifying power of an egg; it only supplies lift. Use it in plain, sugar-and-fat cake batters where eggs were doing the raising, not in custards, sponges or anything that relies on eggs for structure or binding.
- The proportionsOne pound cream of tartar, half a pound bicarbonate of soda, two ounces magnesia, one ounce carbonate of ammonia — a 16:8:2:1 ratio by weight, or roughly 454 g : 227 g : 57 g : 28 g. The cream of tartar to soda ratio of 2:1 is the classic single-acting tartrate baking powder and is chemically sound.
- Carbonate of ammoniaThis is baker's ammonia, or hartshorn, still sold for Scandinavian and German biscuits. It gasses off completely only in thin, dry bakes; in a deep moist cake it can leave an ammoniacal smell and taste. It is a small proportion of the whole here — one ounce in twenty-seven — and may point to use in biscuits and small flat cakes as well as taller ones, though the entry itself says only 'cake making'.
- Powdered magnesiaMagnesium carbonate or oxide, presumably included as a drying agent and anti-caking filler to keep the acid and the soda from reacting in the packet. The quantity in any one dose is very small. Later commercial powders generally used rice flour or cornflour as the filler instead.
- Keep it dry, and mean itThis is the hinge. Cream of tartar and bicarbonate react the moment moisture reaches them, and a damp jar of this powder is spent before you open it. Sift the components together, store in a sealed glass jar away from steam, and test a pinch in warm water before baking with an old batch — no vigorous fizz means no lift.
- How much to useThe original gives the dose only obliquely: one penny packet, equal to four eggs, for two pounds of flour. Modern guidance for a single-acting tartrate powder is roughly 1 teaspoon per 4 oz (115 g) of plain flour, which is a reasonable starting point here, though the carbonate of ammonia makes this mixture not quite equivalent. Weigh rather than scoop; the ingredients differ in density.
- Single-actingUnlike modern double-acting powders, which hold some gas back for the oven, the cream of tartar and soda here release most of their gas as soon as they meet liquid (the carbonate of ammonia, by contrast, works on heat). Mix quickly and get the tin into the oven at once.
- YieldThe full formula makes about 1 lb 11 oz (roughly 765 g) of powder — a great deal for a domestic kitchen. Scaling to a quarter, or an eighth, gives a jar you will use before it goes flat.
Chemical leavening arrived in British kitchens in the middle of the nineteenth century and unsettled the whole economy of baking: eggs were expensive, seasonal and variable, and a penny packet that promised the lift of four of them was a real saving in a working household. Alfred Bird's egg-free custard powder dates from 1837, and his baking powders followed; his firm is often said to have popularised the idea, and by the time Cassell's compiled this dictionary such powders were sold everywhere under proprietary names. The Victorian press ran a long campaign against adulterated food, and cheap packet leaveners were a favourite target for excess soda. Setting out what a sound egg-powder contains, in plain weights, would let a careful housekeeper judge what she was buying or mix her own and know.