The Wisconsin tobacco reporter. (Edgerton, Wis.) 1877-1950, 1912-06-21
Essentials in Tobacco Curing.
PROF. w. w. GARNER, U. S. DEPART
MENT OF AGRICULTURE.

MENT OF AGRICULTURE.
The term "curing, as applied to to-
bacco, is sometimes used to include all
of the processes to which the leaf is
subjected after it has been harvested
in preparing it for the manufacturer.
There are thus included three more or
less distinct processes, namely, the
curing proper Frequently spoken of as
''barn curing"), the fermentation pro-
cess, and the aging process. The term
as herein applied relates only to the
aforementioned process, in which the
tobacco is prepared for fermentation.
In general, it can be said that the
cigar tobacco industry has reached a
high plane of development in this
country. Methods of curing cigar leaf
now in use must be regarded as crude
when compared with those followed
with some other types, notably the
bright flue-cured tObaccOS, nOtwlth-
standing the fact that with this latter
type the general cultural methods are
far from satisfactory. 1t is true that
great progress has been made in the
construction of barns for curing cigar
leaf and many of those now in use in
the wrapper-growing sections are mod
els of perfection, but the method OF
curing which has been in almost uni
versal use in sections growing cigar to-
bacco is air curing; that is, no artificial
heat is used during the progress OF the
process.
More recently open charcoal fires
have come into extensive use in the
Connecticut valley in connection with
the shade tobacco industry, having
been introduced by M. L. Floyd of the
Connecticut Tobacco corporation. With
these exceptions, however, it is only IN
rare instances that artificial heat is re-
sorted to in curing cigar tobaccos.
That the properties of the tobacco
leaf are greatly changed in the curing
is well known to every grower, but the
changes in composition which thus al
ter these properties and the necessary
conditions for bringing about these
changes are little understood. The leaf
when harvested contains from 70 to 80
per cent water, the greater portion of
which is lost by evaporation during
curing. Nevertheless, curing involves
much more than mere drying of the
leaf, for a leaf can be completely dried
in few minutes by applying sufficient
heat and such leaf does not show the
properties of cured tobacco.
In addition to the loss of water there
is marked loss in weight OF other con-
stituents of the leaf, usually amounting
to Is to 30 per cent of the weight OF
8the cured product. Thus, a. hundred
pounds Of green tobacco, containing,
say IS pounds of water, will lose four
to seven pounds of dry matter in cur
ing, in addition to losing more than 70
pounds of the water.
If green leaf be killed with chloro-
form, heat, or other means, such leaf
cannot be cured Curing, in fact, con-
sists essentially in subjecting the living
leaf cells to a process of gradual starv-
alton under proper conditions. The
loss in dry matter represents largely
the material consumed by the cells in
an effort to maintain life as long as
possible and is analogous to the loss in
weight of animals undergoing starva-
ton. The evidence of these changes in
composition brought about by the
starvation and final death of the leaf
tissue consists in the change of the
green color to yellow and, finally, to
brown, the change in texture and the
development of elacticity, and other
properties of cured tobacco.
1t is quite possible to dry the tobac-
co leaf without curing it, and it is also
largely possible to cure the leaf with
out drying it. The two processes may
or may not go hand in hand, depending
on whether the existing conditions
favor both processes. In practice the
problem is to dry the leaf under such
conditions as will best develop the de-
sirable qualities of cured tobacco. 1t
is to be remembered that if the living
cells of the leaf are killed prematurely
the curing is stopped once for all, al
though the drying may continue. I'm
der ordinary conditions the leaf is
killed by the loss Of water, so it is es-
sential that too rapid drying be avoided
in order to afford an opportunity for
the curing changes to take place. On
the other hand, if the drying is too slow
or is delayed too long the curing pro
ceeds too far. The rate of drying is
therefore one of the principal factors
in good curing.
In addition to the loss of water, the
leaf cells may also be prematurely
killed by excessively low or high tenn
peratures or by mechanical injury, such
as bruising the tissue in harvesting.
No portion of leaf which is prema-
turely killed by these or other means
can be successfully cured. It follows
that tobacco which is subjected to
frost, freezing temperatures, or too
high temperatures when artificial heat
is applied, especially in the first stages,
cannot be properly cured.
Aside from the premature killing of
the leaf by extremes of heat or cold,
the temperature plays a very impor-
tant part in affecting the rate of cur
ing. The curing proceeds very slowly
or is stopped completely at tempera-
lures below 60 degrees, while the dry
ing may go on rapidly if the air enter
ing the barn is dry; in other words, the
leaf under these conditions is likely to
dry without curing. On the other
hand, curing proceeds very rapidly at
80 to 100 degrees while the rate Of dry
ing can be controlled by regulating the
humidity in the barn.
1t will thus be seen that the neces
sary conditions for good curing are that
the tobacco be placed in the barn in
sound condition, that the temperature