236 HOPS. 



ducts of combustion to pass direct into the drying chamber, 

 even though the fuel used produces a minimum of smoke 

 {e.g., charcoal). The reason for this is that, apart from the 

 bad effect produced on the hop aroma by these fumes, the 

 temperature of the kiln is very difficult to regulate in 

 the case of an open fireplace. This is the more important 

 on account of the relatively low temperatures — 20° to 35° C. 

 (68° to 95° F.) at the highest— employed, and which are 

 by no means easy to regulate for long. Greater heat must 

 not be used, or the value of the hops will be reduced, and 

 for this reason the practice adopted, e.g., in America, of 

 drying at 60° C. (140° F.) cannot be recommended as worthy 

 of imitation. Heating the drying chamber by hot air or 

 steam is decidedly preferaible to open fires ; and, furthermore, 

 it must not be forgotten that the latter method causes far 

 more danger from fire and consumes a larger quantity of 

 fuel. 



So far as hot-air circulation is concerned, a very brisk 

 current is required in the drying chamber. On the one 

 hand, as a matter of course, the deposition of moisture 

 in the form of dew or drops on the wall of the kiln must 

 be prevented ; but, on the other hand, the ventilation 

 should not be pushed so far as to cool down the drying 

 chamber and thereby retard drying. To obtain favourable 

 conditions for ventilation the kiln is built in the form of 

 a high tower, terminating in an outlet covered by a cowl. 



Through the centre of this opening is led the flue from 

 the heating apparatus, so as to warm the air in the passage 

 and facilitate its escape from the drying chamber. A circular 

 damper of strong sheet metal is also generally placed below 

 this outlet, and, being suspended by chains passing over 

 pulleys and counterpoised at the other end, can be raised 

 or lowered as required, in oirder to reduce or heighten the 

 draught. Sometimes a special ventilating fan or similar 



