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Raspberry Jam
Pick over berries. Mash a few in bottom of preserving kettle; continue until fruit is used. Heat slowly to boiling point and add equal quantity of heated sugar. Cook slowly 45 minutes. Put into sterilized jars or tumblers. Blackberry, gooseberry or other berry jam may be made in this way.
A pre-pectin jam: fruit and an equal weight of sugar, boiled until it sets on its own. The instructions are terse but complete, and two points in them mislead a modern cook.
- Equal quantity means weightPreserving books of this period generally reckoned sugar against the weight of prepared fruit rather than its volume — roughly 1 lb sugar to 1 lb berries. Measuring cup-for-cup gives less sugar by weight than pound-for-pound, and so a noticeably slacker jam.
- Cook to a temperature, not a clockForty-five minutes was normal when kettles were broad, shallow and set over uneven heat. On a modern burner in a heavy pot, raspberry jam usually reaches setting point (220F, or 8F above the boiling point of water where you live) in 15 to 25 minutes. Cooking to the clock past that point gives a dark, caramelised jam.
- The gel testWith no added pectin, confirm the set rather than trusting either time or thermometer alone: drop a little on a chilled saucer, wait half a minute, and push it with a finger. It should wrinkle and hold a track.
- Why the sugar is heatedWarming the sugar first keeps the boil from stalling when it goes in, which shortens the time the fruit spends over heat and preserves colour and flavour. A shallow pan of sugar in a 250F oven for ten minutes is enough.
- Mashing as you goCrushing the berries in layers in the bottom of the pot releases enough juice to prevent scorching before any liquid is added — this recipe has no added water, so the technique is doing real work. Stir often and use the widest heavy pot you own.
- Preserving kettleThe recipe does not say what the kettle was made of; period preserving pans were variously copper, brass, or enamelled granite ware. Any wide, heavy-bottomed non-reactive pot of 6 to 8 quarts works; wide matters more than deep, since evaporation is what thickens the jam.
- Sealing"Sterilized jars or tumblers" meant hot glass — tumblers usually finished with a paraffin cap, jars with a rubber ring and screw cap; paraffin sealing is no longer considered reliable. Current practice is a two-piece canning lid and a 10-minute boiling-water bath, or refrigeration for a jam you will eat within a month.
- YieldAbout 2 lb berries with 2 lb sugar fills roughly four to five half-pint jars. Gooseberries are notably higher in natural pectin than raspberries and will set faster; blackberries are more variable, and ripe ones alone can be sluggish and benefit from a portion of underripe fruit.
Jam of this kind — fruit, an equal weight of sugar, and nothing else — is among the older forms of the preserve, and it depends entirely on the pectin and acid already in the berries. Commercial fruit pectin was patented and marketed in the United States in the 1910s and became widespread in home kitchens through the 1920s, reorganising the jam chapter of cookbooks around short, high-sugar boils; this recipe belongs to the older tradition, where the cook judged the set by eye and the long cook was the only thickener available. That it appears in a book published by a baking powder company reflects the era's promotional cookbooks, which were given away or sold cheaply and covered the whole household repertoire rather than only the sponsor's product. The closing line, offering blackberry or gooseberry as substitutes, is characteristic of the genre: a single method presented as a formula the cook could apply to whatever the season brought.