BY-PRODUCTS 367 



While the amount of fuel necessary to dry a given quantity of 

 fruit will vary according to the conditions of the weather, the effi- 

 ciency of the furnace, the construction of the kiln, the percentage 

 of moisture to be left in the fruit, and various other things, it is 

 roughly estimated that a ton of hard coal will make a ton of dried 

 fruit. Probably the average requirement is more than this. Coke 

 is a little more efficient, 2600 to 2700 pounds of apples being 

 evaporated, it is claimed, by a ton of fuel. 



A good steam system should require considerably less than a 

 ton of soft coal to a ton of dried fruit, one estimate being about 

 half this amount. 



Temperature. A temperature which has been suggested by some 

 operators is 1 50 degrees F. or more when the fruit is first put into 

 the drying compartment, dropping to about 125. degrees as the dry- 

 ing process nears completion. Sufficient and proper provision for 

 controlling the indraft of cold air below the fruit will aid in main- 

 taining the desired temperature. 



Time required for proper drying. A good kiln evaporator 

 should dry a floor of slices in from ten to fourteen hours, twelve 

 hours being the average time. Where the fruit is handled on 

 racks the time required is much shorter, but the conditions 

 are quite different, the fruit seldom being more than two inches 

 thick on the racks ; from four to six hours is the time required 

 for slices. 



It is estimated that quarters will require from eighteen to twenty- 

 four hours in the average kiln, while the time for whole apples 

 will range from thirty-six to forty-eight hours. 



If the atmospheric conditions are heavy and damp the drying 

 is retarded, and under some conditions it is almost impossible to 

 dry the fruit thoroughly. During windy weather it is difficult to 

 regulate the heat, especially if the walls are poorly constructed 

 so that the draft of cold air into the furnace cannot be controlled. 



How far to carry the drying. The fruit should be so dry that 

 when a handful of slices is pressed together firmly into a ball, they 

 will be springy enough to separate at once upon being released from 

 the hand. In this condition, there will be no fruit, or only an 

 occasional piece, that has any visible moisture on the surface. In 

 a slice of average dryness, it should not be possible to press any 



