66. Before the freezer is used, scald the can and the dasher thoroughly with boiling water as shown in Fig. 9, and then set them aside to cool. When entirely cold, fit the can into the freezer, and then, as shown in Fig. 10, pour the mixture into the can. Remember that the mixture should come to within only one-third or one-fourth of the top of the can. With the cover placed securely on the can and the top of the freezer attached, proceed to pack the ice and salt into the freezer. As shown in Fig. 11, fill the space between the can and the container with these materials, using a large spoon for this purpose. Work them down around the can with the small end of a potato masher or similar implement, as in Fig. 12, packing the freezer as tightly as possible and making sure that the ice comes higher than the surface of the mixture inside of the can.
When the packing has been finished, see that the top is securely attached and that the hole in the side of the freezer is well stopped up. Then proceed to freeze the cream. Turn the crank slowly, for nothing is gained by turning the mixture rapidly at the temperature at which it is put into the freezer. After the temperature has been reduced considerably, and just as the mixture begins to thicken a trifle, start turning the crank more rapidly. The air incorporated just at this time by the turning of the dasher increases the volume considerably, for it will remain held in the mixture.
67. PACKING THE MIXTURE.--If the frozen dessert is to be served at once, turn the crank until it is difficult to turn any longer. However, in case the dessert is not to be used as soon as it is made, it should be frozen only moderately hard and then packed and allowed to freeze more. During this second freezing process, a condition occurs that is known as ripening and that improves the quality as well as the flavor of the dessert. After the freezing has been carried on to the desired degree, unfasten the top of the freezer, wipe the can thoroughly around the top with a cloth to make sure that all salt and ice are removed, and then remove the cover. Proceed at once to lift out the dasher and to scrape it clean with a knife or a spoon, as shown in Fig. 13. Push down the frozen dessert in the can carefully and tightly with the aid of a spoon. To prepare it for packing, stretch a piece of waxed paper over the top of the can, replace the cover, and fit a cork into the hole in the cover through which the top of the dasher extends, as Fig. 14 shows. With this done, remove the stopper from the hole in the side of the freezer and, as Fig. 15 shows, run off the brine that has formed by the melting of the ice. Then repack the freezer with a mixture of ice and salt in the proportion of 2 to 1 and set aside until needed.
68. USING A VACUUM FREEZER.--There are some frozen desserts that do not necessarily require the incorporation of air by means of a dasher to be satisfactory. For desserts of this kind, a vacuum freezer, that is, one that requires no turning, may be used.
In such a freezer a container extends down through the center of the can and is surrounded by an air space. The mixture to be frozen is poured into this container from the top and the ice-and-salt mixture that does the freezing is put in from the bottom and takes up the air space. Covers fasten securely both the top and the bottom. A handle attached to one side makes the handling of such a freezer an easy matter.