8 BULLETIN 1141, U. S. DEPARTMENT OF AGRICULTURE. 



such as apples, peaches, plums and prunes, berries, sweet corn, and 

 beans may be dried with equal satisfaction. Such a general-purpose 

 evaporator must necessarily be one of the types employing trays. 

 While a very considerable number of patented evaporators are to be 

 found on the markets, the cash investment necessary to secure such 

 machines is such as to be prohibitive in the caseof many communities 

 in which fruit growing is not a primary business. Consequently, 

 there is very great need for simple, inexpensive drying equipment 

 which can be constructed by an ordinary workman at the place where 

 needed and will give satisfactory results when operated by intelligent 

 amateurs. Of such driers as meet this requirement, the tunnel evapo- 

 rator, described in a subsequent section, is in many respects the most 

 satisfactory. For this reason, the construction of an evaporator of 

 this type, and the nature and amount of equipment which will be 

 required for handling the various fruits, are discussed with special 

 fullness in the section on " The prune tunnel evaporator," page 24. 



BUILDINGS AND EQUIPMENT FOR DRYING. 



The evaporator buildings and accessory equipment described in 

 the following pages are of two types. The kiln evaporator is de- 

 signed specially for the handling of apples in large quantities, and 

 is more widely used for that purpose than all others combined, but 

 it is not well adapted to the drying of other fruits. For this reason, 

 the building of a kiln evaporator in a district which is devoted to 

 general fruit growing would be ill advised. The prune tunnel 

 evaporator, on the other hand, is a general-purpose evaporator 

 which may be employed for drying other materials as well as apples 

 and is consequently better fitted to the needs of a farm or com- 

 munity which may have occasion to dry peaches, prunes, berries, or 

 other fruits. For this and a number of other reasons, which will 

 be pointed out in a subsequent section, a tunnel or modified tunnel 

 drier should be built wherever a community drying plant is needed. 



THE KILN EVAPORATOR. 



The driers used in the farm apple-drying industry of the United 

 States are at the present time almost exclusively of the kiln type. 

 This type of drier first came into use for the drying of fruits in the 

 eastern portion of the United States about 30 years ago, having been 

 derived with some modification from a type of drier long in use 

 in the British Empire and subsequently in the United States for 

 the drying of hops. Its use was at first confined to the drying of 

 raspberries, the drying of apples being at that time conducted in 

 cabinet evaporators. This type was rather rapidly displaced by the 

 kiln drier in that portion of western New York which produces 

 the larger part of the commercial output, and from that territory 

 its use has gradually extended until it is now almost exclusively 

 employed in all districts in which evaporated apples are commercially 

 produced, with the exception of the Pacific Coast States. In 

 Washington, Oregon, and Idaho driers primarily intended for use 

 with prunes are used to some extent in drying apples, although 

 kilns are employed where apples are the chief fruit to be dried. In 

 California, local conditions, such as an ample supply of Asiatic 



