common faults in Flue-curing
the leaf is not dried soon enough it tends to darken in colour
and become harsh, trashy and difficult to condition. Reapings
from the top half of the plant may sponge, while leaf from lower
reapings is more inclined to become spotted and lifeless.
A trace of green leaf in a cure probably shows that colour was
fixed at the correct time.
much green tobacco
Green along the midribs and veins
on a large proportion of the cure suggests that it has not
been yellowed long enough and was reaped green. This can
be prevented in the future cures by reaping riper leaf or opening
the vents slightly later or raising the temperature more
slowly in the range from 100 - 120 ºF.
(ii) A solid green
on the tip end of the leaf is sometimes found on the
lower tiers of the barn. This is usually due to the temperature
being raised too high for a short period in the first 24 hours
of curing. A similar green colour can be caused by Sun
Scald if the leaf is left in the sun after reaping.
(iii) Small green lines,
mostly near the butt end of the leaf, are caused by bruising,
mainly during the reaping and tying. These bruises can
lower the value of the leaf.
some cures the leaf turns to a dull grey or brown colour although
still maintaining normal texture and elasticity. This is
known as sponging and is usually
considered to be caused by drying the leaf too slowly.
Adequate ventilation and even raising the temperature
between 110 - 140 ºF will help to prevent sponging. Certain
types of leaf appear to sponge more easily than others and it
should be remembered that large, heavy leaf reaped when wet
contains water and requires a longer time to get rid of moisture-
or even ventilation - than small, thin leaf.
a slate grey or even greenish colour and the cured leaf often
becomes rather stiff and lacking in texture. The cause and prevention
of this problem are similar to those of sponging, except that
it usually occurs at temperatures over 135 ºF. Advancing
the temperature too fast, or insufficient ventilation, can contribute
the temperature drop or humidity in the barn is too high for the
midrib to dry rapidly, moisture may move out from the midrib into
the already dried leaf. This may produce a dark brown discolouration
along the midrib or, in some cases, a distinct brown line on the
lamina parallel to the midrib.
the leaf is taken from the barn with some of the midribs not completely
cured they will be soft and pliable and larger than the dry midribs.
Under no circumstances should leaf be bulked
in this condition as it will go mouldy. If there are many
fat midribs in the barn, drying should continue at 160
problem is most prevalent in lower reapings from well grown plants,
and types of leaf which do not readily lose moisture. It
occurs on all tier positions. Tobacco should be reaped slightly
greener than normal and a Wilt Cure
used. Ventilation is allowed at the beginning of colouring
in order to encourage an early loss of moisture and ensure wilting
after 24 hours.
It may be necessary to introduce moisture in
the form of wet bags to prevent the bottom tier fixing green.
The air should be to lose much more moisture throughout the
colouring period than normal, so that the lamina begins to dry
when 155 ºF is reached. subsequent drying may then be
very rapid to fix the colour.
during the colouring period
is carried out when growers have difficulty in curing their tobacco
due to the mixed reapings and excess moisture in the leaf.
Initially, tobacco is hung in the barn for 36 hours with all the
vents and doors wide open. This is not a fixed time as a lot depends
on the condition of the tobacco when it is reaped. During
the first eight hours or so of this period it is essential
to try and get all surface moisture of the leaf to enable a natural
wilt to start.
After this initial hanging the doors of
the barn are shut and the temperature is taken up to 85 ºF with
all the vents open. This second phase, which takes
12 - 18 hours, should produce a fully wilted leaf which has
started to colour and which hangs flaccid, allowing air
to circulate from top to bottom.
Once this wilted tobacco begins to turn yellow,
all the vents are shut and the temperature is then taken up
to 95 ºF to get full colouring. This period lasts from
2 - 4 hours and the grower must watch this tobacco carefully
during this phase as the full colouring comes quickly.
Finally the drying process begins. The
vents are re-opened and temperatures freshened up fairly rapidly
at the rate of 5 ºF every 4 hours until 160 ºF have been reached.
With this method the rate of drying is much quicker as this
type of wilt and colouring allows the leaf to open up.
It becomes more porous, giving a more open-grained leaf, from
which the moisture is easily removed. By curing this way,
Barn Rot and leaf
discolouration are eliminated.