THE CUBA REVIEW 27 



It is the policy of most of the sugar companies in Cuba to purchase a consid- 

 erable portion of the cane going through their factory from outside growers who live 

 sufficiently near the sugar mill. This policy encourages the planting of cane by 

 individuals within a convenient radius. These growers are called "Colonos". 



At the beginning and close of the crop, the sugar content of the cane is usually 

 at a minimum. It is always the endeavor to grind cane during the period of the 

 maximum sugar content, although where large areas are involved, it is necessary to 

 commence cutting in the early part of December and extend operations to the middle 

 of September. The average crop season, however, may be considered as from the 

 middle of December to the end of June. Weather conditions in Cuba, which vary 

 considerably from year to year and also in different parts of the Island in any one 

 year, materially affect the length of the grinding season and the sugar output of 

 both the Island and the individual provinces. 



II.— SUGAR FACTORY IN CUBA 



A sugar factory in Cuba is termed a "Central". Without attempting to describe 

 the many minor processes, the ordinary method of manufacturing raw sugar from 

 cane may be considered under four general heads: 



1. Extraction of the juice 



2. Clarification 



3. Evaporation 



4. Separation of the crystals 



The term "sucrose" is a theoretical one, indicating a sugar content of 100% 

 purity. The final product of a "Central" is raw sugar of a light brown color, polar- 

 izing 96°, or sugar 967c pure. Polarization is the method of determining the per- 

 centage of sucrose by the use of an instrument commonly known as the polariscope. 



The percentage of juice extracted based on the total juice in the cane indicates 

 the milling or grinding efficiency. The sucrose recovered from the sucrose extracted 

 indicates boiling efficiency. The sucrose recovered in 96° test sugar from total 

 sucrose in cane denotes general factory efficiency. These figures are of great value 

 and interest to the factory management as they serve as a guide in the manufactur- 

 ing operations. 



On the arrival of the cane at the sugar mill, or "Central", it is lifted from the 

 railroad cars by an electric crane and is weighed while suspended above the cane or 

 feed hopper. After the cane has been weighed, it is dropped into the feed hopper and 

 is passed to the crusher by means of a link belt conveyor, after which it goes through 

 the mills. 



The average milling plant consists of two grinding units or tandems paralleling 

 each other, each comprising a crusher (consisting of two corrugated rolls) and three 

 three-roller mills, each tandem being known as a nine-roller mill. Some of the most 

 modern plants are equipped with three and, in some instances, four tandems, each 

 tandem comprising a crusher and four three-roller mills (some tandems even having 

 five three-roller mills). The crusher resembles a mill, but the surface of the rolls is 

 corrugated, so as to cut and partly crush the cane. This crushing operation facilitates 

 the work of the mills and the extraction of the juice. The United Fruit Company 

 has adopted the double crusher and nine-roller mill, which is an original idea of its 

 Superintending Engineer. Its Centrals at Banes and Preston are equipped with four 

 and three tandems, respectively. 



In the average "Central", each mill consists of three horizontal steel rolls from 

 four and a half to seven feet long and from twenty-four to thirty-six inches in dia- 

 meter, set with parallel axles as shown in the foregoing sketch. The rolls are set in 

 adjustable bearings and the cane passes between the top roll (A) and the first bottom 

 roll (C), and then between the top roll and the second bottom roll (B), which are set 

 closer together so that the cane is actually crushed twice in each mill. The cane 



