ICE CREAM MAKING 533 



the machine, and the finished ice cream out at the other. The 

 freezing is done by the passage of brine through the disks which 

 revolve rapidly in the cream as it is being crowded to flow from 

 one end of the machine to the other. This type of machine is 

 open and in some respects offers advantages not possessed by 

 the closed machines, especially in giving the operator oppor- 

 tunity to use the thermometer more accurately in the freezing 

 process, which is a distinct advantage. This type of machine 

 is made in different sizes with both single and double sets 

 of disks. 



It should probably here also be noted that the use of a brine 

 freezer is not restricted to the plants having artificial refrigera- 

 tion. The brine for circulation through disks or around the 

 freezer may be provided either from the large brine tank of the 

 artificial cold storage system, or may be produced at will by the 

 mixing of salt, ice, and some water in the brine box which ac- 

 companies the machine if desired. This brine is then forced 

 by a small pump to circulate and do the work of freezing. 



THE FREEZING PROCESS 



The freezing mixture almost universally used consists simply 

 of common salt and ice. Salt is deliquescent, that is to say, 

 has an affinity for water and attacks the ice to procure the 

 water for which it craves. However, any change of any body 

 from the solid to the liquid state, no matter what the body is, 

 is accomplished only by the absorption of heat. Ice is melted by 

 heat ; butter melts on a warm day ; iron. is melted in the fierce 

 heat of the converter. Now the ice in the freezer is melted by 

 heat, and this heat is obtained where it can be got most readily ; 

 some from the air, some from the surrounding walls of the freez- 

 ing tub which, being made of wood, which is a poor conductor, 

 permits but little to be obtained from that direction, but prin- 

 cipally from the relatively warm cream-sugar mixture within the 



