Agriculture Reference
In-Depth Information
yarn and fabric properties (Hunter, 1993). They also deter-
mine to a large degree both the value and the actual product
into which the raw material will be converted. Consequently,
instruments and standard methods (described in the Annual
Book of the American Society for Testing and Materials
[ASTM] Standards, Section 7, Volumes 07.01 and 07.02
[ASTM International, West Conshohocken, PA 19428-
2959] and in the International Wool Textile Organization
[IWTO] Specifi cations [the Woolmark Company, Ilkley,
England]) have been developed and are in common use to
accurately measure most of the value-determining proper-
ties. For mohair and cashmere down, these include average
fi ber diameter and its distribution; average fi ber curvature
and its distribution; clean yield; vegetable matter content
and type (measured on most commercial lots); staple
length and its distribution; staple strength and its distribu-
tion (measured on very few commercial lots); color, luster,
style, and character (measured on few if any commercial
lots, subjectively assessed on most). The variability inher-
ent in these natural fi bers necessitates special techniques
be used when sampling commercial quantities of fi bers to
ensure accurate and reliable results. Typically core and
grab samples are removed from individual fl eeces, bags,
and bales in a specifi ed manner.
be separated from the guard hair by the dehairing machine
(which is actually not possible).
Average Fiber Diameter and Distribution,
Medullation, Average Fiber Curvature
and Distribution
Historically, determination of average fi ber diameter and
medullation involved sampling, conditioning, and reduc-
tion of samples to very small, short (250
m), but still
representative test specimens that were measured manually
under high magnifi cation (500
μ
) using a projection micro-
scope (PM). The measurements were time consuming and
quite expensive. Average fi ber diameter alone was esti-
mated by an airfl ow technique that was faster than the PM
method but was little used with mohair and cashmere.
During the past 20 years, methods using automatic image
analysis (such as the Optical Fiber Diameter Analyzers
[OFDA] 100 and 2000 [BSC Electronics Pty. Ltd., Ardross,
Australia]) and laser measurements (such as Sirolan-
Laserscan, CSIRO, Geelong, Australia) have been devel-
oped and used extensively. These instruments are capable
of providing very accurate estimates of average fi ber diam-
eter and distribution and average fi ber curvature and dis-
tribution, and the OFDA 100 is also capable of estimating
medullation (white and pastel shades only) in a short time,
therefore breeders, marketers, and manufacturers now
commonly use these inexpensive measurements for assist-
ing with selection, marketing, and processing decisions,
respectively.
Of particular note for the cashmere industry are the
results of a recently completed study (McGregor and
Butler, 2008) that showed 86% of the variability in perfor-
mance and effi ciency of the dehairing process was
explained by measured attributes of the raw material. Raw
cashmere that processed most effi ciently and produced the
longest dehaired cashmere tended to be white, longer, and
have higher fi ber curvature and lower VM than average,
as well as having normal (that is, comparable in length to
or slightly longer than the down fi bers) length guard hair
and no visible cotting. Effi ciency of processing was sub-
stantially decreased with increasing average fi ber diameter
irrespective of color.
×
CLEAN YIELD TESTING
A typical procedure would be that described in ASTM
standard test method D 584. In summary, samples of raw
fi ber drawn from a commercial lot or a fl eece in a specifi ed
manner are weighed, scoured, dried, and reweighed. The
oven - dry, scoured fi ber is then subjected to three more
gravimetric tests to determine residual grease, ash content,
and vegetable matter content. This permits calculation of
fi ber base and vegetable matter base in the original raw
material. These “base” numbers are usually adjusted
upward by incorporating specifi c amounts of “ allowable ”
moisture, ash, and grease into the base value and calculat-
ing several commercial yield values, for example, clean
mohair fi ber present in the U.S.
MECHANICAL YIELD TESTING (CASHMERE)
Modifi ed Shirley analyzers, cards, and custom-built min-
iature dehairing machines have been used to estimate the
amount of cashmere down that can be mechanically sepa-
rated from the scoured raw material. However, a method
that has likely found the most use involves measuring the
fi ber diameters of a representative raw sample from which
the percentage of fi bers 30
Average Staple (or Fiber) Length and Distribution
A ruler was the traditional means for manually measuring
staples or individual fi bers that had been straightened and
laid on a black felt board. Numerous instruments were
developed to automate this process and remove subjectiv-
ity. However, to date, very little mohair and cashmere is
measured objectively for length except by scientists for use
m and fi ner can be calculated
(Lupton et al., 1995). This represents a theoretical
maximum yield that assumes all fi bers 30
μ
μ
m and fi ner can
