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How to Freeze
Scald can, cover and dasher, adjust can in freezer; put in dasher; pour in the mixture to be frozen and fasten cover (the can should never be more than 3/4 full); adjust crank and turn once or twice. Fill space around can to within an inch of top with ice and salt (three parts crushed ice to one part salt), packing hard. Turn slowly at first, increasing speed when mixture begins to stiffen. As the ice and salt are reduced by melting, add more as required. When mixture is very firm, wipe off cover, open can and remove dasher; scrape frozen mixture from dasher and sides of can, and pack down solidly; cover with paper and replace can cover. Put cork in opening in cover. Pour off salt water if there is danger of its getting into the can. Fill up over top of can with ice and salt (four parts ice to one part salt). Cover freezer with heavy blanket and keep in cool place until ready to serve.
This is the master method that the frozen-dessert chapter assumes you already know: how to run a hand-crank ice-cream freezer. The custard or fruit mixture comes from elsewhere in the book; everything here is about the machine, the brine and the hardening.
- The hinge: salt lowers the brine below freezingIce alone sits at 32F and will never freeze a sugared custard. Salt dissolving in the meltwater drops the bath to roughly 0 to 10F, and that is what pulls heat out of the can. Skimping on salt is the usual reason a batch never sets.
- Two different ratios, on purposeThree parts ice to one part salt for churning: a fast, cold bath. Four to one for packing afterwards: less salt, so a slower-melting bath that holds the dessert firm without the brine draining away in twenty minutes.
- Use rock salt, by volumeUse rock salt -- "Salt" here almost certainly means coarse rock or ice-cream salt, and the parts are presumably reckoned by volume, though the book does not say. Table salt dissolves too fast and is an expensive way to do the same job.
- Three-quarters full is not caution, it is overrunChurning beats air into the mixture and it expands. A can filled to the brim produces a dense, heavy result and forces mix past the cover into the brine.
- Scalding the can and dasherAt the time this was written, this was the sanitizing step for equipment that would hold an unpasteurized dairy mixture at temperatures bacteria like on the way down. Wash and scald anyway; a cold-rinsed dasher does nothing for the texture and something bad for the keeping.
- Slow at first, then fastSlow turning while the mixture is still liquid lets a thin layer freeze evenly against the can wall. Speeding up once it stiffens keeps the ice crystals small, which is the whole difference between ice cream and a sweet ice block.
- Timing the original omitsA gallon can in a well-packed freezer takes about 20 to 30 minutes of steady cranking to reach the "very firm" stage. The crank going stiff is the reliable signal, not the clock.
- The cork and the brine lineThe cork plugs the hole the dasher shaft came out of. Keep the brine level below the can lid and pour off meltwater as instructed; salt water that finds its way in ruins the batch and is not recoverable.
- Packing is the ripening stepAn hour or two under blanket and salted ice firms the texture and lets the flavor settle. In a modern kitchen this stage is simply a covered container in the freezer, and an electric churn replaces everything from "adjust crank" onward, though the three-to-one brine still applies to bucket-style machines.
The hand-crank freezer described here is a nineteenth-century American object: a wooden bucket, a metal can, a dasher and a geared crank, packed with ice and rock salt. The design is generally credited to Nancy Johnson, who patented an "artificial freezer" in 1843, with the crank-and-gear improvements that made it a household item following over the next few decades. Before it, ice cream was worked by hand in a pot set in a salted ice bath, scraped and beaten with a spatula, which is why the dish belonged to confectioners and rich houses with ice-houses. By the time this book was printed, commercial ice delivery and cheap rock salt had put a freezer on many back porches, and cookbooks could print a single "how to freeze" page and then run through a dozen custards, mousses and water ices without repeating themselves. The final instruction, to bury the can and cover the whole thing with a heavy blanket, is a reminder that there was no home freezer waiting: the dessert had to hold itself cold until dinner.