40 



be taken that the tobacco does not turn black for lack of sufficient 

 air, reduction instead of oxidation taking place. 



The nature of the processes which take place in the curing of 

 tobacco have not yet been fully worked out, but in a general way 

 there is a loss of water — about 80 per cent of the green weight of the 

 leaves — and a modification of the chlorophyll and other compounds of 

 the leaf and the resulting change in color from green to yellow, then 

 to red and brown. 



If the leaves are cured in a current of hot air the water is quickly 

 lost and the color remains green, because sufficient time has not been 

 allowed for the biological processes which cause the color changes to 

 take place. If the leaves remain longer in the hot-air current they 

 may also lose their fermenting power. Even after restoration of the 

 excessive loss of water only a slight fermentation can be produced. 



In order to facilitate the transformation of the matter in the leaves 

 a slow curing is necessary. If, however, the circulation of air is too 

 limited or stopped, reduction takes place and the leaves become 

 spotted and, if no ventilation is given, very soon turn entirely black 

 and lose their resistance and elasticity and finally become worthless. a 



Specific rules for the curing of tobacco can not be given, for much 

 depends on the weather conditions and the character of the crop and 

 shed. In a general way ventilation should be slow, with a constant 

 circulation of air around all of the leaves until the parenchyma 

 changes color. Rapid ventilation should be avoided during the early 

 stages of curing, except for short periods after very damp spells, which 

 may be resorted to in order to drive out the excess of moisture. High 

 temperature and excessive humidity must be avoided. 



The time of curing usually ranges from twenty-five to thirty-five days. 

 The process should cease when suitable color is obtained, bearing in 

 mind that the colors are modified to a certain extent in the process of 

 fermenting. When the curing is completed it is well to close the venti- 

 lators during the day and open them wide at night, in order to bring 

 the tobacco into a moist condition before removing it from the poles. 

 None should be removed until the reduction of the midrib is complete. 

 If the curing has been slow and the conditions favorable, the colors 

 at the time of removing from the poles should be fairly uniform. It 

 is advisable, however, upon taking down the tobacco to iin mediately 

 put it into small piles, which favors uniform fermentation and also 

 further increases the uniformity of color. In no case should tobacco 

 be allowed to remain in the curing shed very long after it has been 

 completely cured. 



The curing of the whole plant is effected with nearly as good results 



a The writer noticed in Porto Eico as well as in Cuba cigars of which the 

 wrapper was covered with black spots. It is thought that this was caused by 

 the lack of ventilation at certain periods while tobacco is in the shed. 



