THE CULTURE OF FLUE-CURED TOBACCO. 30 
stopper, to be closed or opened more or less as the conditions of 
curing require. 
Generally it will be found best to begin to open these ventilators 
and raise the heat somewhat before the tobacco is fully yellow, so 
that the moisture will be sufficiently exhausted by that time to pre- 
vent reddening or sponging. The draft should not be too strong, 
especially at first, but it should be sufficient to effectively remove the 
air before, or at least by the time, it becomes saturated. 
In light-bodied tobacco, as grown on the lighter soil types, the 
yellowing process will generally take about 36 to 48 hours under 
average conditions; but if the tobacco is very heavy and dark, as 
frequently occurs on the filler soil types in the western part of the 
Old Belt section, it may be necessary to consume three or four days 
in the yellowing process. This will be especially necessary if the 
soil on which the tobacco was grown was rich in ammoniates or if the 
tobacco was a little underripe when harvested. Under these cir- 
cumstances there will be an abnormal quantity of reserve nitrogenous 
food material in the leaf, and it will be necessary to avoid applying 
much heat for several days or drying the leaf much, in order that 
these food materials may be consumed by the life processes of the 
plants, else the tobacco will be rank smelling, dark, and objection- 
able rather than sweet and agreeable. This explains why it is such 
a common practice with those who grow tobacco on the more clayey 
soils of the western part of the Old Belt to let the tobacco hang in 
the barn for a day or two before any fire is used at all and then to 
keep the temperature comparatively low so as to prolong the yellow- 
ing period, which in this case is really a ripening or sweetening 
period as well. 
When the yellowing of the leaf is approximately completed, dur- 
ing the later stages of which the temperature has been maintained 
perhaps at from 110° to 120° F., it is then the custom to move up 
the temperature quite rapidly, say at the approximate rate of 24 
degrees per hour, to 130° or 135°, and to hold it at that point until 
the leaf itself is entirely dry throughout the barn, or at least on the 
bottom poles. It isa general rule of curing that it is not safe to exceed 
this temperature for any length of time before the leaf is dry, because 
at about this temperature, or a little above, the cells of the leaves are 
rapidly killed, and when killed they at once release the moisture they 
contain, which comes immediately to the surface and results at once, 
by oxidation, in a blackish discoloration known as scalding. Scald- 
ing may occur at a much lower temperature than this when the 
tobacco is full of sap, in the early stages of the cure. When the leaf 
is dry throughout the barn the ventilators may be partially or per- 
haps wholly closed, to save fuel, and the heat gradually moved up 
at the rate of about 5 degrees per hour to about 175° for the light, 
