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SUGAR-CANE SIRUP MANUFACTURE 95 
When operating during the day only, the evaporator must be 
cooled and held partly full of juice or water overnight. This can be 
satisfactorily accomplished by flooding the pan with juice while the 
furnace is hot (taking care, of course, that ie pan does not boil dry 
at any time) and skimming the juice with care before leaving it over- 
night. Even with the most careful skimming, however, a deposit will 
be found on the bottom of the pan the next morning, and if the juice is 
undisturbed when the furnace is fired, the heat will cause this deposit 
to stick to the bottom of the evaporator, producing a sirup of darker 
color and poorer flavor. This difficulty can be largely overcome by 
scraping the bottom of the pan and stirring the juice before firing the 
furnace, thereby returning the deposit to suspension. When the 
sediment is thus loosened from the bottom and sides of the pan, part 
of it can be removed by skimming and the rest can be run out with the 
first few gallons of sirup made. ‘The removal of this sediment gives a 
cleaner and brightersirup. ‘Too much carecan not be taken in keeping 
the pan clean; dirty pans are responsible for much low-grade sirup. 
When starting with water or juice in the pan, careful regulation of 
the evaporator is necessary for the continuous flow of juice and sirup. 
Starting with the pan full of juice is probably the more difficult pro- 
cedure, because the juice is at practically the same density over the 
entire length of the pan. As evaporation continues, however, and 
more juice is run into the pan, the sirup can be forced to the proper 
end of the evaporator. Dipping juice or sirup of low density to parts 
of the pan where the sirup is becoming too dense is bad practice, but 
is sometimes unavoidable at the start. As soon as sirup is being 
finished in the back compartment of the evaporator and there is 
a continuous decrease in density toward the front end, it is time to 
permit a continuous flow of juice. The rates at which juice is run into 
the evaporator and sirup is run out are now controlled by the sirup 
maker. Most of his time is occupied in keeping the flow well reeu- 
lated. His station is at the sirup end of the pan, where he can 
constantly watch the density of the sirup during the final stage of 
concentration and correct any irregularities. The sirup maker 
should caution the fireman when he needs the fire tended; a steady 
fire is necessary to regulate the evaporator. 
When starting the operation after water has’ been left in the pan 
overnight, juice is run into the front or lower end as usual. ‘The 
water is partly evaporated, partly displaced, and partly mixed with 
the thickening juice. Consequently some sirup will be mixed with 
the last of the water that is displaced or forced out; this can be caught 
and returned to the evaporator. The juice seldom boils in the first 
compartment, which is the coolest part of the evaporator, unless for 
some reason the inflow of cold juice is temporarily stopped; this juice 
has a smooth, cool surface, over which the scum forms a blanket and 
is occasionally removed with a perforated skimmer. When the 
furnace is properly constructed the boiling of the juice increases in 
vigor toward the back end of the pan as far as the section under which 
the fire is the hottest. This causes the scum to run, counter to the 
flow of juice, to the cooler or front portion of the evaporator. The 
Juice is boiled over the sides to the skimming trough and flows back to 
the front of the pan. A portion of theskimmings remains in the trough 
and the remainder flows to the front of the pan, where it is removed. 
By the time the juice reaches the hottest part of the pan, which is 
about 114 feet beyond the middle, it has been evaporated to semisirup 
