LAC CROP:
The lac insects repeat its life cycle twice in a year. There are actually
four lac crops since the lac insects
behave in two ways either they develop on Kusum plants or devlop on plants
other than Kusum. The lac which grows
on Non-Kusum plants is called as “Ranjeem lac,” and which grows on Kusum plant is called as “Kusumi lac.
Four lac crops have been named after four Hindi months in which they are cut from the
tree. They are as follows:
Ranjeeni Crop:
(i)
Katki: Lac larvae
are inoculated in June-July. Male insect emerges m August-September. Female give rise to swarming larvae in
October-November and the crop is reaped in Kartik (October and November).
(ii)
Baisakhi: Larvae produced by Katki crop are inoculated in October-November, male
insects emerges in February-March,
females give rise to swarming larvae m June-July, the crop is reaped in Baisakh (April-May).
Kusumi Crop:
(i)
Aghani:
Lac larvae are inoculated in June-July, male insect emerges m September,
female give rise to swarming larvae in January-February and crop is reaped in Aghan (December-January).
(ii)
Jethoi:
The larvae produced by Aghani crop is inoculated in the month of January-
February, male emerges in
March-April, female give rise to swarming larvae in June- July and the crop is
reaped in the month of Jeath (June-July).
The time of
infection with swarming larvae, the time of emergence of male insects, the time
of reaping the crop, and the time of
producing swarming larvae by female etc., are shown m tabular form below -
HARVESTING OF LAC:
Harvesting is the process of collection of lac from host plants. It is
done by cutting the lac encrusted twigs when is crop is mature. It may be of two types:-
a) Immature harvesting In Immature harvesting, lac
is collected before swarming, and lac thus obtained
is known as ‘ARI LAC’. The immature
harvesting has drawbacks, as the lac insects
may be damaged at the time of harvesting. However, in case of palas lac
(Rangeeni lac), it is found that ARI
Lac gives better production. Hence, ARI lac harvesting is recommended in case of palas
only.
b)
Mature harvesting -In mature harvesting, lac is collected
after swarming. The lac obtained
is known as mature Lac. To know the exact date emergence
and swarming of nymph, a simple visual
method is adopted.
A yellow spot develops on the posterior
side of lac cell towards
crop maturity. This spot spread forwards until it covers half of the cell. Cutting of twigs for harvest can be done at any time between
the stages while yellow spot occupies one third to one half of the cell area. It is sometimes desirable to wait till the emergence of the first few nymphs.
The harvesting periods
of different crops
are different. The kartiki crop is harvested in Oct. /Nov.;
baisakhi, in May/June;
aghani in Jan/Feb.;
and jethwi, in June/July. When the nymphs
have escaped from the brood lac, what is left is the stick lac or phunki lac. These sticks should be tied in bundles
and immersed in water, preferably running water for 3- 4 days, keeping
them well under waters with help of heavy stones.
The stick lac should then be kept in shade for drying.
Scraping and Processing
of lac:
Lac encrustations
are removed from the twigs of host plant by scraping. after which they should not be exposed
to sun. Various forms of lac are obtained at different stages
of their purification. These are-
1.
Stick lac -The raw lac
thus obtained is known as raw or crude
lac or scraped lac or stick lac. This
crude lack consists of resin, encrusted insect body, lac dye, sand and twig
debris. The freshly scraped lac
contains a lot of moisture and usually left to dry. The quality and value of stick lac depend very much upon variety of
factors, viz. host tree, climate, whether the crop is harvested before or after emergence of larvae, and the method of
drying and storage. The stick lac
can not be stored for longer duration, as the lac has high moisture content and
therefore tendency to form lump, and become low quality.
2.
Seed lac -The
scraped lac is grinded in hard stone mills. The unnecessary materials are
sorted out In order to remove the
finer particles of dirt and colour, this lac is washed repeatedly with cold water. Now at this stage it is called as “Seed lac” and is exposed to sun for drying.
3.
Shellac-The
shellac is the finished and purified product and is commonly used across the world. Seed lac is processed into shellac
by any of the three methods: hand made country Process or heat process or solvent process. In melted process the seed lac is melted
by steam heat. The molten soft lac is
squeezed through filter by means of hydraulic pressure. The filtered molten lac is drawn into long and
continuous sheets with help of roller. The sheet is then broken into pieces called flakes. Colour or
different chemicals may be mixed during melting process for particular need. Commercially available
shellac are Orange shellac, Lemon one shellac, Orange fine shellac etc.
COMPOSITION OF LAC:
The major constituent of lac is the resin. Lac resin is a polyester
complex of straight- chain hydroxy
fatty acids of C14 – C18 carbon chain (such as Aleuritic acid, butolic acids),
mono- and dihydroxy acids along
with hydroxy terpenic acids. Other constituents present are : dye, wax, sugar, proteins, soluble salts, sand,
woody matter, insect body debris etc. Lac wax is a mixture of anthroquinoid derivatives. . The approximate percentage of different constituents of lac is given below:
Resin – 68
to 90%
Dye – 2 to 10%
Wax – 5 to
6%
Mineral matter – 3 to 7%
Albuminous matter – 5 to 10%
Water – 2 to 3%
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