Methods for Measuring Microns
By Angus McColl. Yocom-McColl Testing Laboratories, Inc.
Objective fiber testing can be a powerful marketing and genetic selection tool
when used properly. Objective measurement is an assessment made without the
influence of personal feelings or prejudice. Visual appraisal and fiber
handling are fundamental aspects of fiber judging, but are very weak appraisal
methods for accurately identifying average fiber diameter. Instrumentation can
accomplish the measurement of fibers with accuracy in the tenths of a micron
(one millionth of a meter). The difference between a sample averaging 20.5
microns and one at 22.5 microns is very small in physical terms, but it is
critical in terms of commercial use and pricing structure.
Fiber testing technology gives breeders a useful tool to analyze fiber and track
the progress of their selection programs. The determination of average fiber
diameter helps identify the best end use for fiber and is information that
mills require before making their purchasing decisions.
The ability to provide accurate information on fiber quality places natural
animal fiber producers in a stronger position to sell their fiber for what it
is worth. Very few people buy and sell commodities without knowing everything
they can about them. Information is power in the marketing world, and objective
fiber assessment provides it.
Instruments in the Lab
There are four approved instruments and methods, the most widely used
instruments now being OFDA 100 (See Photo 1), and Sirolan LaserScan. Their
development followed many years of use of the Airflow and Projection
Microscope, which are both still in use. Test methods are approved by the
International Wool Testing Organisation (IWTO) and the American Society for
Testing and Materials (ASTM) and are performed in laboratories under standard
conditions for testing textiles, i.e., 70° F, and 65% relative humidity (+2%
RH). Yocom-McColl in Denver, CO has all four instruments, but performs fiber
diameter testing using only LaserScan, OFDA 100, and microprojection.
Sirolan LaserScan, (CSIRO), and Optical Fibre Diameter Analyser, (BSC
Electronics) were both developed in Australia. These two instruments are
calibrated using Interwoollabs tops, the only recognized supplier of
calibration tops to the worldwide textile industry. A diagnostic and
calibration check is performed each day on both instruments. For samples
averaging 26.0 microns and finer, the accuracy of measurement is plus or minus
0.2 microns when the tests are performed properly under standard conditions.
The LaserScan instrument measures fibers by dispersing individual snippets (two
millimeter lengths of fiber) in a solution of isopropanol and water and this
fluid transports the fibers through a glass cell where each one intersects a
laser beam. The LaserScan measures the change in the signal generated when the
shadow cast by the fiber snippets falls on a light detector. The signals, which
are directly proportional to the fiber diameter, are recorded electronically
and analyzed almost instantaneously by computer.
Optical Fibre Diameter Analyser (OFDA)
OFDA 100 (See Photo 2) was approved as an IWTO standard in 1995. Mark Brims and
his company, BSC Electronics, designed the instrument. It uses a video camera
to produce electronic images of magnified fibers which are distributed over a
horizontal glass slide. Software analyzes the fiber images and derives
measurement of diameter of a large number of longitudinal fiber sections. OFDA
100 also measures and calculates the distribution of fibers (SD and CV) as well
as average fiber diameter and several other fiber diameter related
characteristics. Both of these methods provide the wool and textile industry
with high volume testing applications.
Airflow (See Photo 3) measures the flow of air through a sample of wool and
provides an indirect measurement of average fiber diameter. It does not give
measurements of standard deviation and coefficient of variation and must be
calibrated using wool samples that were originally measured by microprojection.
Airflow assumes wool density is always constant, and this has caused problems
with wools that are less dense (particularly those containing medullated
fibers). According to the Australian Wool Testing Authority (AWTA), Airflow can
also be affected by large variations in Coefficient of Variation (CV),
providing coarser results with a large CV and a finer result with a lower CV.
It was the normal measurement for micron results in Australian wool auctions
until the summer of 2000.
The projection microscope provides the only primary reference method available
for the direct measurement of the mean fiber diameter and distribution of wool
fibers. All other instruments are calibrated using standard wool samples where
the diameter and distribution values have been determined using the Projection
Microscope. (See Photo 4) Projected fiber images are individually measured at
500X magnification. However, this method is time consuming and expensive and
only used occasionally nowadays for special jobs.
Portable Instruments (OFDA2000 and Fleecescan)
OFDA2000 and Fleecescan are two instruments developed in Australia for on-farm
fleece testing with the objectives of separating superfine wool from flocks of
fine-wool sheep and assisting with genetic selection based on fineness
characteristics. The reason for the former practice is a premium paid for
superfine wool. One of the problems of measuring purely for marketing reasons
was in many cases when the superfine wool was removed from the clip, the
remaining wool had a higher micron with a lower market value. The additional
labor and testing expense to separate the superfine wool is not always
The OFDA2000 and Fleecescan are not approved by IWTO or ASTM. Wools separated
into different micron ranges by these instruments still have to be core sampled
and tested by IWTO and/or ASTM approved methods and instruments when offered
The OFDA2000 measures the dimensions of raw (i.e., greasy and dirty) fibers and
then uses a constant correction factor (within a “mob”) to estimate the true
dimensions. This correction factor is measured and calculated on-site and is
typically the average of 30 samples. Since the cleanliness of every sample
measured is different, this practice limits the accuracy of individual
The OFDA2000 has a built-in compensator for temperature and relative humidity
that adjusts for the ambient air at the testing location. Thus it can only be
properly used on samples that have been given time to reach equilibrium with
the ambient air. OFDA2000 is not suitable for testing raw, unconditioned
samples at a central location since raw samples from different areas of the
country contain varying amounts of moisture that affect fiber diameter. Also,
it would not be possible to use an appropriate grease correction factor. The
only way to accurately test wool or other animal fibers is for the samples to
be washed, dried, and conditioned at standard conditions for testing textiles,
a worldwide requirement.
The OFDA2000 tests fewer than 100 fibers (depending on the fiber diameter and
staple length) from tip to base in five millimeter increments for a total of
about 1500 measurements.
It produces a fiber profile reflecting aging, health/production status, and
environmental conditions the animal was subjected to during the growth of that
particular staple length. Typically, a mid-side sample is measured to estimate
the average fiber diameter of the whole fleece. Other (more accessible)
locations (e.g., the pin bone) have also been investigated.
The OFDA2000 uses the same basic technology as its parent the OFDA 100 with the
exception of measuring multiple fibers in profile. The OFDA 100 is actually
capable of measuring one fiber at a time in profile but this measurement is
slow and tedious, and probably only used by researchers.
The Fleecescan is transported in a trailer. This system minicores each fleece
and chemically cleanses the sample that is then tested on a specially designed
LaserScan heavily protected to avoid damage as it is being moved.
Genetic Selection Tool
Yocom-McColl uses both LaserScan and OFDA 100 to test fiber of individual
animals. We can measure average fiber diameter, diameter distribution, spin
fineness, curvature, curvature distribution, and comfort factor on the
LaserScan. Using the OFDA 100, we measure all of the above plus medullation on
white or light-colored animals. Comfort factor is the percentage of fibers
greater than 30 microns subtracted from 100 percent (in other words, a
marketer’s positive “spin” on the original term “prickle factor”.
We test individual animals using two millimeter snippets obtained across the
base of the two inch square submitted sample. In this way, we are able to
provide estimates of the genetic uniformity of the sample at a precise
The Laserscan and the OFDA 100 test from 2,000 to 4,000 individual snippets per
sample either core sampled (minicored) or guillotined. When guillotined at the
base of the staple, all fibers measured were produced at the same time and in
the same environment. Such a measurement indicates the genetic fineness and
uniformity of the animal (at a specific age) that can be extremely valuable for
Neither LaserScan nor OFDA measure relaxed staple length. Yocom-McColl measures
average staple length on an Agritest instrument according to IWTO 30 on
relaxed, conditioned staples.marketplace. I believe that any initiative that
make’s alpacas more productive in the long run will ultimately benefit every
breeder. I do not at all agree that breed standards will hurt individual
breeders. Breed standards are a herd improvement tool.
In Reno the panel members made it clear that, for breed standards to be
successfully established in our industry, there has to be “buy in.” The members
must feel that standards are inclusive not exclusive. And whatever goals,
guidelines or standards that are adopted must allow for change and become an
What’s next? I would like to see a task force appointed by the ARI and AOBA
Boards of Directors. I think the task force should include a representative of
each of the affiliates; a board member from AOBA and ARI; a member of the
Alpaca Show Rules Committee; a member of the Judges Training Committee and; one
or two senior alpaca judges. I also would like to see the continuing
participation of the panel led by Dr. Ames.
I would hope that the task force could meet in Kentucky at the 2004 AOBA
convention. They would be charged with creating a process for examining the
issue of breed standards.
In the end I would urge that the process result in a Breed Type Conference held
at the 2005 joint ARI/AOBA Fiber to Fashion Conference in Orlando, Florida. Dr.
Ames says that these types of conferences are the traditional vehicle for
livestock breeds who wish to establish or update breed standards. A typical
conference would last for a day or two and would allow all of the
“stakeholders” to have their say.
Once the conference was complete the industry could decide whether or not to
adopt standards and if so, what the standards should look like. It is like the
saying on Fox News, “You Decide.”