Glossary of Terms
Links to glossary by letter
accuracy - a measure of the closeness of a test result to the true value. The difference between accuracy and precision should be noted. (Also see bias, precision and confidence limits.)
airflow - a method of measuring the Mean Fibre Diameter of a sample of wool in which a test specimen (a measured mass of the scoured, dried and carded sample), after exposure to a conditioning atmosphere, is compressed to a fixed volume and a current of air is passed through it. The rate of flow is then adjusted so that the pressure drop across the sample equals a predetermined value. The rate of flow is an indicator of the mean fibre diameter of the wool in the sample. The instrument is calibrated to international standard wool tops of known fineness.
appraisal - an estimate of the value-determining characteristics of a parcel of wool, based on subjective judgement but sometimes assisted by objective measurements.
area of dust - the area of dust as a percentage of the total staple area. (Also see colour of dust.)
area of wool - the area of wool as a percentage of the total staple area. (Also see colour of wool.)
“as is” colour - the colour of wool without any cleaning of the sample. It may be expressed using tristimulus values or by two measurements, brightness and yellowness, derived from the tristimulus values. (Also see clean colour and base colour.)
ash content - the residue of a scoured wool subsample after it has been subjected to charring followed by heating to 800oC. It is expressed as a percentage of the subsample mass and is taken to represent the dirt (sand and soil) not removed during the scouring of the greasy subsample.
ATLAS (Automatic Tester of Length And Strength) - a computer-controlled instrument which measures the Staple Length, Staple Strength and Position of Break of individual staples. In operation, a continuous belt conveys each staple between an array of lights and an array of photocells, which detects the ends of the staple and enables the length (in millimetres) to be measured. The staple is then grasped by two sets of jaws and broken. The force required is measured in Newtons. The two pieces of the broken staple are individually collected and weighed and, from the masses, lengths and core test yield, the staple linear density (thickness) is calculated and expressed in kilotex; the Staple Strength is expressed as Newtons/kilotex (N/ktex). The masses of the two pieces are also used to calculate the Position of Break.
average linear density - the clean staple mass per unit of Staple Length at standard conditions.
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bale - see conventional bale.
baling surfaces - the two surfaces upon which the main baling pressure has been applied to a bale. This usually means the cap and base of a bale.
base (when referring to a wool bale) - the permanently closed end of a wool bale on which baling pressure is applied. (Also see cap.)
base (when referring to a staple) - the end shorn from the skin of the sheep. (Also see tip.)
base colour - the inherent colour of greasy wool after the removal of residual contaminants eg. grease, dirt, suint and vegetable matter; or the contaminants following laboratory scouring, e.g. grease, dirt, suint and vegetable matter. (Also see base colour and clean colour.)
bias - a constant or systematic difference between a true value and corresponding test results. (Also see accuracy and precision.)
branding substance - a coloured (pigmented) product which may be a liquid, a spray, crayon or chalk, used to mark sheep for identification purposes.
break - a marked thinning of all the fibres in a staple, which produces a position of weakness; it is caused by sickness or stress, lack of nourishment, or a sudden change in the sheep’s environment. (Also see position of break and tender wool.)
brightness - a measure of the intensity of reflectance of a surface in the green spectral region; one method of expressing brightness is in terms of the Y tristimulus value. (Also see yellowness.)
bulk (when referring to sale lots) - the main portion of a lot (in contrast to the sample).
bulk (when referring to wool measurement) - the space-filling capability of clean, carded wool. Bulk is expressed as the volume to which a defined pressure compresses a defined mass of wool. (Also see laboratory card and resistance to compression.)
bulk classed lot - a lot of raw wool comprising bales containing wool blended from various sources, the wool being from one country of origin.
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canary stain - a bright yellow stain in a fleece, which is not removed by normal scouring processes.
cap - the end of a wool bale on which baling pressure is applied, normally closed by pinned flaps but which may be opened for inspection of the contents. (Also see base.)
carbo (or carbonising) wools - wools, typically short-stapled, with vegetable matter content so high that it cannot be removed economically by mechanical treatment; for such wools, the first treatment is usually carbonising.
carbonise - to treat wool with sulphuric acid, followed by baking, which embrittles burrs present so that they can be easily broken up, crushed and removed.
card sliver - a continuous strand of opened and loosely assembled scoured wool fibres, together with variable amounts of vegetable matter. Its linear density is approximately constant and it is without twist.
character - a subjectively-assessed characteristic of greasy wool related to crimp and staple definition.
check test - verification of documentation and calculations forming the basis of the IWTO Test Certificate on which a doubt has been raised and, if possible, a set of additional measurements made in accordance with the same standard IWTO Test Method as was adopted for the original test. Check testing is restricted to tests carried out by the Test House which conducted the original test. (Also see data verification and check test result.)
check test result - the result obtained by carrying out a check test. It may include all or part of the original test data, or it may be entirely new data or a combination of both. It is the result to be certified if the previous result is withdrawn.
classed grower lot - a lot of raw wool from an individual grower comprising bales classed from one clip.
clean colour - the colour of wool after scouring. It may be expressed using tristimulus values or by two measurements, brightness and yellowness, derived from the tristimulus values. Both brightness and yellowness can affect the dyeing potential of the wool. (Also see “as is” colour and base colour.)
coefficient of variation (CV) - a statistical measure of the variability exhibited within a set of values. It expresses the standard deviation as a percentage of the mean; the higher the CV, the greater the variability.
The coefficient of variation of a sample may be calculated from:
Coefficient of Variation is often measured for Fibre Diameter and Staple Length.
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colorimeter - an instrument used to determine the colour of wool by measuring the tristimulus values of the sample. (Also see spectrophotometer.)
colour - is determined by the tristimulus values as defined in the 1971 Commission International de l’Eclairage (CIE) publication, for illuminant D65 and the 10o observer. (Also see brightness and yellowness.)
colour of dust - the average colour of the dust area of a staple, categorised as brown, grey, red or pink. (Also see area of dust.)
colour of wool - the average yellowness (Y-Z) of the wool area of a staple. (Also see area of dust and colour.)
combing wool - wool suitable for conversion to yarn on the worsted system. Generally it is merino wool having a staple length of about 40 mm or greater, or crossbred wool having a staple length of about 75 mm or greater.
comfort factor - the percentage of fibres finer than 30 micron in a sample.
commercial yield - any of the yields, calculated from the Wool Base, Vegetable Matter Base and Hard Heads and Twigs Base as specified in Section 3.0 of the IWTO Core Test Regulations. Yields may be expressed either as net clean mass of a lot or delivery, or as the net clean mass expressed as a percentage of the net greasy mass.
conditioning atmosphere - a volume of air, capable of being maintained at standard temperature or humidity, or both, in which specimens are conditioned in accordance with IWTO-52. For wool testing this is usually a temperature of 20±2oC and a relative humidity of 65±3%. (Also see standard conditions.)
confidence limits - an expression of the precision of the mean of a set of values, usually associated with a stated probability, most often 95%. It is the interval around the mean within which, with the stated probability, the true value is expected to lie.
consignment - synonymous with delivery.
conventional bale - a bale of undumped wool of approximately 0.75m x 0.75m x 1.25m and weighing between 110 and 204kg. (Also see dump.)
core - all the material removed by a coring tube in one core-sampling operation. (Also see core sample.)
coresample - a representative sample of raw wool obtained from each bale in the lot by coring techniques.
coretest - the series of measurements, typically of Wool Base, Vegetable Matter Base and Mean Fibre Diameter, carried out on a core sample.
coring machine - equipment which uses hydraulic power to drive one or more pressure coring tubes into a bale of wool so that the tube reaches at least 93% of the length of the bale. Cores are automatically ejected from the tube.
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coring tube - a tube of circular cross-section which is equipped with a sharpened, replaceable tip. The tip enables the tube to penetrate a bale of raw wool without rotation, remove a cylindrically-shaped portion of the wool and retain it without change in material or moisture content.
When part of a coring machine, the coring tube must penetrate at least 93% of the length of the bale. When operated manually, the tube must penetrate at least 47% of the length of the bale.
Very small diameter coring tubes may also be used to obtain fibre snippets for fibre diameter testing. (Also see minicore.)
cotted wool - wool that has become partially felted on the sheep’s back; wool with a matted appearance.
crimp - the waviness of a fibre, expressed numerically as the number of complete waves per unit length; crimp is usually taken as an indicator of mean fibre diameter, the higher the number of crimps per unit length, the finer the wool. (Also see curvature.)
crimp definition - the degree of alignment of the crimp waves within a staple.
crimp frequency - the number of crimp waves per centimetre of Staple Length.
crossover error - an error generated when the results of two tests are transposed, either completely or in part.
A crossover is distinct from a testing error and does not indicate an error arising from laboratory testing procedures.
curvature - a measure of crimp reported as degrees/mm. (Also see crimp.)
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data verification - verification of documentation and calculations forming the basis of an IWTO Test Certificate on which a doubt has been raised. (Also see check test.)
delivery - a bulk of raw wool covered by a single IWTO Test Certificate. If previously untested, all bales are sampled and tested as a group. If the component lots have been tested individually, the test results may be combined in accordance with IWTO-31.
display box - an open box large enough to hold and display a grab sample of wool for appraisal and evaluation purposes.
display sample - the grab sample taken from a single lot when it is placed in a display box.
documentation error - an error in clerical procedures such as recording data, calculation, typography or data transmission.
dump - the process of compressing bales, usually of greasy wool, to a density exceeding 500 kg/m3 and restraining them with bands or wires.
dumped bales - bales prepared for transport overseas by the process of dumping.
ethanol alcohol extractives - material capable of being removed from a scoured sub-sample by reflux distillation with ethanol. It is taken as indicating the grease and wax remaining on the sub-sample after scouring. It is usually expressed as a percentage of the oven dry mass of the sub-sample.
fault - contamination, especially Vegetable Matter, in greasy and in semi-processed wool.
fibre diameter - the thickness of individual fibres; it is customary to quote an average value (Mean Fibre Diameter or MFD) in micrometres. (Also see fibre diameter distribution and micron.)
fibre diameter distribution - the distribution of fibre diameter in a wool sample. Distribution can be expressed in the form of a frequency table or as a frequency Histogram with data grouped into classes of one micrometre size, and integer micrometre values as midpoints of the class intervals.
The results may be expressed in a number of ways including Standard Deviation, Coefficient of Variation and the percentage of fibres coarser or finer than a given value, such as 30 µm.
fineness - see fibre diameter.
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grab machine - a mechanical device capable of operating a set of jaws, which penetrate into the side of a wool bale and withdraw a representative grab sample of suitable mass. The jaws withdraw the entire sample in such a way as to avoid contamination of the wool by pack material, and to avoid damage to the pack.
grab sample - the greasy wool drawn from a bale by a single operation of a grab machine.
grease - wax component extruded from the wool follicles.
greasy wool - wool from the sheep’s back or sheepskins which has not been scoured, solvent degreased or carbonised or otherwise processed. It contains grease and suint extruded from the follicles in the skin and dirt & Vegetable Matter picked up from grazing
Hard Heads and Twigs Base (HH%) - the oven-dry mass of ash-free, ethyl alcohol extractives-free hard heads and twigs, expressed as a percentage of the mass of the sample.
hauteur (H) - the average of the length-biased distribution of fibre length in a top. It is obtained by sorting a sample of the sliver into length classes and calculating the average of the number of fibres of each length class. Hauteur is usually regarded as a numerical average although this assumes no relationship between fibre length and fibre diameter.
histogram - a method of graphing the distribution of individual measurements.
individual test - a standard certifiable test on a lot of wool, carried out in strict accordance with an approved IWTO Test Method.
interlot - a lot of raw wool comprising bales matched before testing, normally from different clips, the wool being from one country of origin.
IWTO Combined Certificate - a certificate resulting from the mathematical combination of IWTO Test Certificates, calculated in accordance with the appropriate IWTO Test Method.
IWTO Combined Certificate (by Subtraction) - a certificate resulting from the mathematical subtraction of a separately tested and certified component from a consignment which is covered by an IWTO Test Certificate or an IWTO Combined Test Certificate, calculated in accordance with the appropriate IWTO Test Method.
IWTO Test Certificate - a certificate resulting from the testing of samples drawn in accordance with the relevant IWTO Test Regulations, and in accordance with the appropriate IWTO Test Method.
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keeper samples - see test house samples.
keratin - the main constituent of wool. It is a complex of fibrous proteins characterised by high sulphur content with cystine being the predominant amino-acid present. Cross-linking between the cystine residues makes keratin more stable and less soluble than most proteins.
kilopascal (kPa) - the unit of pressure in the SI system is the pascal (newton per square metre). This unit proved to be inconveniently small for many purposes and the kilopascal (kPa), equal to 1000 Pa, is more commonly used. One pound per square inch is equivalent to 6.895 kPa.
kilotex (ktex) - the linear density of a staple expressed in grams per metre. It is the unit of thickness used in calculating Staple Strength for which the unit is Newtons per kilotex.
laboratory card - a machine capable of simulating the action of a commercial carding machine. (Also see Shirley Analyser.)
laboratory sample - the material which will be used as a basis for carrying out the measurement in the laboratory. It may be the total sample or it may be derived from the total sample by sub-sampling.
Laserscan - an instrument that detects shadows of fibre snippets in a laser beam as they are carried in solution through the beam, developed for improved performance in measuring Mean Fibre Diameter and fineness distribution.
licensed laboratory - a laboratory licensed by IWTO to issue IWTO Test Certificates. (Also see test house.)
An essential pre-requisite for licensing is that the laboratory is accredited by a recognised national laboratory accreditation body to ISO Guide 25 and that the national accreditation body itself enjoys a Mutual Recognition Agreement with similar institutions in other countries, in conformity with ISO Guide 57.
In addition, the laboratory must be situated in an IWTO member country and must be scrutinised and approved by the IWTO Licensing Panel.
linear density - the mass of clean fibre per unit length of a staple at standard conditions.
lot - any number of bales of wool, of similar mass and dimensions, prepared for sale as a single parcel in accordance with accepted trade practices.
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maximum probable difference - the maximum difference which can be expected between two mean results measured successively by the laboratory, or two mean results obtained by two different laboratories.
maximum retest range - the difference between the values of a retest and the original Test Certificate or an earlier retest which, if exceeded, is deemed to indicate the likelihood of an error.
mean - arithmetic average; the mean of a set of values is calculated by dividing the sum of those values by the number of them. (For example, see mean fibre diameter).
The mean of a sample may be calculated from:
mean fibre diameter - the arithmetic mean of all fibre diameter readings in a sample.
mechanical tuft sampling machine (MTS) - a device used to obtain, by mechanical means, representative tufts of staples from a grab sample.
micrometre - a unit of length measurement equal to one-millionth of a metre; it is the unit of measurement for the fibre diameter of wool. It is commonly called a micron.
The symbol ‘µm’ is used for micrometre.
micron - commonly used name for the unit of measurement of fibre diameter, correctly termed a micrometre (µm).
mid-side sample - a shorn wool sample of approximately 30 grams taken from the mid-side of a sheep.
minicore - a sub-sample obtained by small-diameter coring tubes to provide a representative snippet sample of sufficient mass.
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newton - the unit of force in the SI system; a force of one kilogram is equivalent to about 9.8 newton (N).
noil - the short fibres removed during the combing process; it comprises second cuts, pieces of broken fibres, neps, and is contaminated by small pieces of vegetable matter. (Also see top.)
objective measurement - a system in which the characteristics of greasy wool are specified by measurement rather than by descriptive terms resulting from subjective appraisal.
objectively matched lot (OML) - a lot of raw wool comprising individually tested classed grower lots exclusively matched after testing and certified only as agreed by IWTO and in accordance with the specific national restrictions.
objectively matched interlot (OMI) - a lot of raw wool containing individually tested Classed Grower Lots and one individually tested Interlot comprising a maximum of four single bale Classed Grower Lots, matched after testing and certified only as agreed by IWTO and in accordance with the specific national restrictions, the wool being from one country of origin.
OFDA (Optical Fibre Distribution Analyser) - an instrument for measuring fibre diameter mean and distribution using automated microscope and image analysis techniques.
oven-dry mass - the mass of material obtained by scouring a sample and exposing it to air at 105oC until equilibrium is reached, and corrected for the moisture content of the drying air.
position of break (PoB) - an indication of where a staple breaks during extension, determined by comparing the masses of clean wool in the broken portions of the staple. It does not imply that a break exists in the staple.
precision - an indicator of the repeatability of a measurement; it is often expressed in terms of confidence limits. (Also see accuracy.)
projection microscope - an instrument for measuring fibre diameter mean and distribution. Magnified images of the profiles of short lengths (snippets) of fibre are projected on a screen and their widths measured by using a graduated scale.
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raw wool - wool fibre together with variable amounts of vegetable matter and extraneous alkali-insoluble substances, mineral matter, wool waxes, suint and moisture. It includes-
(a) greasy wool;
(b) wool which has been scoured, carbonised, washed or solvent degreased;
(c) scoured skin wools; and
(d) slipe wools.
recore check test - a set of measurements, made in accordance with the relevant Test Methods, on a further sample of raw wool drawn from the delivery as part of the check testing procedures. A recore check test may only be conducted where a Certificate has not been delivered in relation to a contract.
recore test - a set of measurements, made in accordance with the same standard test method as that adopted for the original test, on a further coresample of raw wool drawn from a lot for which the test result is in doubt. Such sample material must be obtained by resampling bales in accordance with current sampling Standards or regulations. The recore test result must be adjusted for any declared or observed change in net greasy mass of the lot.
regain - the mass of moisture in a mass of textile fibres determined under prescribed conditions, expressed as a percentage of the clean oven-dry mass of fibre. Most wool is traded on the basis of its mass at regains specified by IWTO Regulations.
The IWTO Standard Regain is19% for Tops combed in oil and 18.25% for Tops dry combed.
regrab test - a set of measurements made in accordance with the same standard test method as that adopted for the original test, on a further grab sample of raw wool drawn from a lot for which the test result is in doubt. Such sample material must be obtained by resampling all bales in accordance with the IWTO Staple Test Regulations.
resistance to compression - the force per unit area required to compress a fixed mass of scoured and carded wool to a fixed volume. The result is expressed in kilopascals. (Also see bulk.)
retest - a set of measurements made, in accordance with the relevant IWTO Test Methods, on a further sample of wool drawn from a delivery for which the original Certificate is in doubt. This differs from a recore check test in that duplicate coresamples, or duplicate samples and duplicate sets of staples, are drawn for possible testing by two separate Test Houses to resolve a disputed result. Such sample material must be obtained by recoring or grab sampling where applicable and reweighing all bales, in accordance with the IWTO Test Regulations.
romaine - the amount of noil produced during combing expressed as a percentage of the total top and noil. (Also see tear.)
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sale lot - a number of bales of similar mass and from the same country of origin, containing greasy wool prepared for sale according to accepted trade practices. (Also see interlot, lot and objectively matched lot.)
sample - the wool drawn by appropriate methods from a lot, bulk or delivery. In order to issue IWTO Test Certificates, the sample must be drawn in strict accordance with the relevant IWTO Test Regulations to ensure that it is representative.
sample container - a container constructed so that there is no loss of material or undue exposure to the atmosphere, i.e. the sample stored therein shall not show a material change in its moisture content during storage before weighing.
scoured wool - wool that has been aqueously washed or solvent washed to remove most of the grease, wax and suit and dirt.
sealed container (for grab samples) - a container which is closed in a manner which prevents unauthorised interference with the contents.
sealed container (for coresamples) - a container which is impermeable to moisture so that the contents are maintained without change to their moisture content.
second cut - a staple resulting from shearing an area on a sheep which has already been shorn. A second cut differs from a normal staple in that both ends are severed and no tip end is evident. In Staple Length measurement second cuts are considered as staples.
shirley analyser - a laboratory card used for removing vegetable matter from scoured wool and blending the fibres for subsequent measurement.
snippet - very short pieces of fibre, typically around 2 mm long, which have been cut to measure Fibre Diameter and related properties. (Also see minicore, Laserscan, OFDA and projection microscope.)
spectrophotometer - an instrument used to measure the reflectivity of a surface within the visible spectrum.
It may be used, as an alternative to a colorimeter, to measure the colour of clean wool.
standard conditions - standard atmospheric conditions used to normalise test conditions for measurements, which are affected by temperature or humidity. For most wool measurements the standard conditions are a temperature of 20 ± 2oC and a relative humidity of 65 ±3%. (Also see conditioning atmosphere.)
standard deviation - a measure of dispersion of individual results. Standard deviation is expressed in the units of measurement. (Also see variance and coefficient of variation.)
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staple - a well-defined bundle of fibres which has been removed from a mass of greasy wool as a unit. In Staple Length and Staple Strength measurement, staples are considered to include second cuts.
staple axis - an imaginary line along a staple in the direction of the majority of its component fibres.
staple length - the length of a staple projected along its axis obtained by measuring the staple without stretching or disturbing the crimp of the fibres.
staple strength - the maximum force required to rupture a staple per unit of average linear density. (Also see ATLAS.)
sub-sample - the randomly drawn portion, representative of a sample from a lot to be tested, used for a specific test measurement.
suint - water soluble component (sweat) extruded from the wool follicles.
tear - the mass ratio of top to noil produced by combing. (Also see romaine.)
tender wool - wool for which a significant proportion of staples exhibit a marked weakness, at corresponding points in all the fibre of the staples. (Also see break, position of break.)
test - a set of measurements made on a sample of raw wool, in full accord with an IWTO test method.
test house - a laboratory which carries out tests in accordance with the current IWTO test methods and regulations. In order to issue IWTO Test Certificates the laboratory must be a licensed laboratory.
test house samples - in testing, that portion of raw wool retained by the test house after a test has been conducted (also known as keeper samples).
test result - the result which is obtained by applying a standard test method to a sample obtained in accordance with a standard sampling method and is-
(a) shown on a Test Certificate;
(b) issued by a test house; or
(c) a component of a combined Certificate.
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test specimen - a randomly drawn portion from and representative of a sub-sample, to be used for a specific test measurement.
testing error - an error in laboratory testing procedures.
tip - the end of a staple opposite to the end shorn from the skin. (Also see base.)
tip length - the number of millimetres from the staple tip to a point where the staple width is 75% of the average staple width.
Note: tip length is based on the amount of wool present in the tip; it does not reflect staple tip shape.
top - sliver that forms part of the starting material for the worsted and certain other drawing systems, usually obtained by the process of combing, and characterised by the following properties:
(a) A substantially parallel formation of the fibres, essentially free of vegetable matter.
(b) The absence of fibres so short as to be uncontrolled in the preferred system of drawing.
(c) A substantially homogeneous distribution throughout the sliver of fibres from each length group present.
total alkali-insoluble matter - the oven-dry, ash-free, ethanol-extractives-free, alkali-insoluble matter present in a test specimen (expressed as a percentage of the mass of the test specimen). It comprises vegetable matter, together with any skin, dags, pack material, string and paper.
total sample - a representative sample of wool obtained by coring bales of raw wool. When issuing an IWTO Certificate, sampling must comply with the IWTO Core Test Regulations.
transport container - a lockable or sealable container in which samples are transported.
tristimulus value - one of the three reflectance readings obtained when using a colorimeter; specified by the Commission Internationale de l’Eclairage (CIE) as X (red), Y (green) and Z (blue). Y and Z are used in specifying the clean colour of wool.
true value - the absolute value of a characteristic for a bulk, e.g. a lot or a consignment; it is almost always unknown. Measurements of the characteristic are, in the absence of bias, normally distributed about the true value with a variance that is also unknown in a particular case. The mean of a set of measurements is the best estimate of the true value.
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tuft of staples - a bundle of wool consisting of approximately 1 to 20 staples drawn in one action.
variance - the variance of a sample is the square of the standard deviation and is a measure of the distribution of values around the mean. It is expressed in the units of measurement squared. (Also see coefficient of variation.)
The variance of a sample may be calculated from:
vegetable matter - burrs (including hard heads), twigs, seeds, leaves and grasses present in wool.
Vegetable Matter Base (VMB%) - the oven-dry mass of ash-free, ethanol-extractives-free burrs (including hard heads), twigs, seeds, leaves and grasses present, expressed as a percentage of the mass of the sample.
Wool Base (WB%) - the oven-dry mass of wool fibre free from all impurities, i.e. ash-free, ethanol-extractives-free and free from all vegetable matter and other alkali-insoluble impurities, expressed as a percentage of the mass of the sample.
yellowness - the difference between the reflectances of a surface in the green and blue regions of the spectrum, expressed as the difference between the tristimulus values Y and Z; it is reported as (Y-Z). (Also see brightness and colour.)
yield - the amount of clean fibre, at a standard regain, that is expected to be produced when a delivery of raw wool is processed. The yield may be expressed both as a clean mass in kilograms and as a percentage of the mass of raw wool prior to processing.