VACLTM PAXS. 355 



a granular rather than a glassy look, showing the presence of the 

 minute grains of sugar ■which are formed during the cooling. 



Another method is to observe the character of the escaping steam, 

 which no longer is continuous, but, as the time of striking for sugar ap- 

 proaches, is in large bubbles, escaping with a puff much resembling 

 the boiling of hasty pudding, or the last boiling iu making maple 

 sugar. 



In the vacuum pan, however, after a certain degree of concentra- 

 tion is reached, the temperature is no longer sufficient to hold all the 

 sugar in solution, and the excess is at once thrown down in the form of 

 an infinite number of microscopic crystals distributed through the boil- 

 ing mass. The appearance of this grain is carefully watched for by the 

 sugar-boiler; and, after its appearance, the contents of the pan and 

 the progress of the evaporation receives his constant supervision. The 

 object to be secured is now, by re2:»eated additions of ''pan-liquor" (as 

 the semi-syrup, with which the vaccum pan is at first charged and 

 afterward fed, is termed), to " build up," as they say, the small crystals 

 of sugar, or " grain," until they are of appreciable size, so that their 

 purging in the centrifugal may be easily accomplished. The dangers 

 are that, either through increased heat in the pan, by partially losing 

 the vacuum, or by the two great amount of pan liquor admitted in a 

 charge, and the consequent considerable dilution of juice, he may lose 

 the grain by its being dissolved, and he must again recover it, as at the 

 outset ; or, by a too rapid evaporation, and the consequent excessive 

 deposition of sugar, it may liappen that the sugar is thrown down more 

 rapidly than it can be deposited upon the crystals already formed, and 

 a fresh crop of crystals is produced, known technically as " false 

 grain." 



This " false grain" is very carefully guarded against by the sugar- 

 boiler, and may be dissolved by a heavy charge of pan-liquor and a high 

 heat in the pan. But it may happen when the pan is already so full as 

 to forbid further addition of fresh liquor ; in which case, it can only be 

 removed by means of heavy washing with water in the centrifugal or 

 mixer, thus causing a great loss of sugar in the molasses. 



In working the vacuum pan, the vacuum is first created by the 

 pump, when the semi-syrup is drawn into the pan, until the first coil 

 of pipe is covered, when the steam may be turned into such coil, and, 

 as the successive coils become covered with the syrup, steam is admitted 

 to them. It then remains only to add fresh portions of the semi-syrup 

 as evaporation progresses, until the grain is formed, when the exeicise 

 of more care is needed. After a time the full capacity of the pan is 

 reached, and it is then necessary to remove the contents of the pan, 



