Manufacturing Processes for Wool Based Yarns | Production Processes for Wool Yarns

Wool is the fiber derived from
the hair of domesticated animals, usually sheep. Wool is classified
according to the source from which it is obtained. The fleece or the
wool which is collected is kept to the different stages of manufacturing
process which starts with the preparation of the fiber. The different
stage through which it is taken depends upon whether the fiber is intended for worsted or woolen yarns. The flow chart for the manufacturing process is as follows:

Preparation Wool

Fleeces
vary from 6 to 18 pounds (3-8 kg) in weight. The best quality wool is
obtained from the sides and shoulders and is treated as one fleece.
Similarly, the wool obtained from the head, chest, belly, and shanks is
treated as a second fleece.

Preparation Wool

The
raw wool or newly sheared fleece is called grease wool because it
contains the natural oil of the sheep. When grease wool is washed, it
loses from 20 to 80 percent of its original weight. The wool obtained
should be carefully sorted into different grades.

Sorting and Grading: In
sorting, the wool is broken up into sections of different quality
fibers, from different parts of the body. The best quality of wool or
one fleece is used for clothing; the lesser quality or second fleece is
used to make rugs. Each grade is determined by type, length, fineness,
elasticity, and strength. The wool may be graded according to the type
of merino sheep or according to fineness or diameter which is otherwise
called as United States System and British System.

The
classification according to the United States System or according to the
type of merino sheep from which it is obtained is as follows:

• First quality wool is identified as fine and is equivalent to the
  quality of wool that could be obtained from a full-to
  three-quarter-blood Merino sheep.


• Second quality is equivalent to the kind of wool that could be obtained from a half blood Merino.


• The
  poorest qualities are identified as common and braid; they are coarse,
  have little crimp, relatively few scales and are somewhat hair like in
  appearance.


• The grading system on the world market is based upon
  the British numbering system, which relates the fineness, or diameter,
  of the wool fiber to the kind of combed, or worsted, yarn that could be
  spun from 1 pound of scoured wool.


• The first in quality would be
  that wool which is fine enough for and capable of being spun into the
  highest wool yarn counts of 80s, 70s, and 64s (No. of 560 yards in 1 
  pound).


•  The second quality is fine enough to be capable of being spun into yarn counts of 62s, 60s, and 58s.
  
  


• The poorest grade is capable of being spun into yarn counts of only 40s and 30s.

TableComparative Wool Grading Table

United States System	British System
Fine (full-to-three-quarter-blood)	80S, 70S, 64S
Half – blood	62S, 60S, 58S
Three – eights – blood	56S
Quarter – blood	50S, 48S
Low – quarter – blood	46S
Common	44S
Braid	40S, 36S

Scouring: Wool taken
directly from the sheep is called “raw” or “grease wool.” It contains
sand, dirt, grease, and dried sweat. The weight of these contaminants
accounts for about 30 to 70 percent of the fleece’s total weight.
Wool
scouring is the first step in the conversion of greasy wool into a
textile product. It is the process of washing wool in hot water and
detergent to remove the non-wool contaminants and then drying it. The
scouring machine contains warm water, soap and a mild solution of soda
ash or other alkali. They are equipped with automatic rakes, which stir
the wool. Rollers between the vats squeeze out the water. If the raw
wool is not sufficiently clear of vegetable substance after scoring, it
is put through the carbonizing bath of dilute sulfuric acid or
hydrochloric acid to burn out the foreign matter.

Drying: Wool
after scouring should not be allowed to become absolutely dry. About,
12 to16 percent of the moisture is left in the wool which would enable
handling of the fibers in further processing.

Oiling: Wool
is unmanageable after scouring and hence the fiber requires to be
treated with various oils to keep it from becoming brittle. Oiling of
the fibers also helps to lubricate it for the spinning operation.

Carding:
From this stage, further processing depends on whether woolen or
worsted yarns are to be produced. The main objective of carding is to
disentangle and to open the scoured wool. Carding also forms a web of
disentangled fibers that are formed into sliver.