94 



Picking, Drying, and Packing Hops. [may. 



(i) Temperature of the Air— The strength of the draught 

 depends upon the difference in temperature between the air 

 inside the oast and the air outside the oast. If the air outside 

 the oast is nearly as warm as that within the oast, the draught 

 will be weak, whereas, if the air inside is very hot and the 

 air outside cold, then the draught will be strong. The tem- 

 perature of the air outside the oast cannot be controlled, and, 

 therefore, the hotter the air inside the oast the greater will 

 he the draught. It must be remembered, however, that very 

 hot air must not be allowed to pass through the hops at the 

 beginning of drying because of the danger of "reeking" 

 them. 



(ii) Height of Oast.— The strength of the draught is pro- 

 portional to the height of the column of air that produces the 

 draught, thus, there is a better draught in a tall oast than 

 in a low one. It is for this reason that factory chimneys are 

 built so high. In an oast it is important that the height of 

 the oast, both from the floor to the hair and from the hair 

 to the cowl, be great, since the hot air in both parts influences 

 the draught. 



(iii) Strength of Wind. — If a strong wind is blowing there 

 is seldom any trouble in obtaining a good draught, provided 

 that the cowl is pointing in the right direction. 



If the air is still and foggy, much greater difficulty is 

 experienced in obtaining a draught, and under these condi- 

 tions it is most important to have the cowl pointing away 

 from whatever wind there may be, otherwise, the least bit 

 of wind blowing into the cowl is sufficient to stop the draught 

 and spoil the hops. 



Temperatures of Hop-Drying. — The temperature at which 

 hops are being dried can be easily controlled by the use of a 

 thermometer. The thermometer should be placed so as to 

 register the temperature just below the hops, i.e., the point 

 at which the hot air first comes in contact with the hops. 



There are various kinds of thermometers in use for Hop- 

 Drying. One very useful kind of thermometer is described in 

 a leaflet * published by the South-Eastern Agricultural Col- 

 lege. It consists of an ordinary thermometer fixed to a 

 wooden rod; this is pushed into a hollow iron rod, which is 



* The Temperatures of Hop-diying. Price id. 



