Cob RE: Hemp: Long

[Jack C. Thompson]

Since posting a reply earlier I've gone back into my files and pulled the
following report up.  It's pretty long, even after I snipped much of the
discussion about fiber preparation and economic discussions.  The complete
report may still be available from the following web site:

                http://fornits.com/no-zone/

I haven't checked, and if it has gone away, I'd be happy to send to entire
report to individuals rather than clog up the list.


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The following is an abstract presented to the Industrial Hemp Conference in
Toronto, Ontario, Canada, March 25th, 1996
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Bioregional Development Group

THE ECOLOGY CENTRE, HONEYWOOD WALK CARSHALTON, SURREY SMS 3NX, England TEL:
+44 (0)181 773 2322 FAX: +44 (0)181 773 2878

HEMP TEXTILES IN BRITAIN - OPPORTUNITIES FOR BIOREGIONAL DEVELOPMENT
Sue Riddlestone

Abstract

        Hemp (Cannabis sativa) could be an important crop enabling the
production of environmentally-friendly, locally produced, high quality
textiles. Hemp is a traditional fibre crop which for centuries was
important in meeting our needs for textiles, paper and oils. It is easy to
grow organically, that is, without a need for artificial pesticides,
herbicides or fertilizers, so it can make an important contribution to a
sustainable future. Currently the bulk of our demand for textiles is met by
cotton and synthetics, both of which have serious environmental problems
associated with them.

        The once major hemp textile industry has now completely disappeared
from the western world. At Bioregional Development Group we have been
investigating the potential for reviving hemp and flax cultivation and
integrated processing to produce textiles, paper, particleboard and oils on
a sustainable basis in our bioregion, The Weald of Surrey, Kent and Sussex
in Southern England.

        As part of our work, as a practical experiment we grew a small
trial crop of hemp specifically for textile production. We processed the
crop in a variety of ways, by hand, using conventional flax machinery and a
novel decorticator to produce yarn which was woven into fabric. This had
not been done in the UK for many years and was a very interesting and
worthwhile experience.

(snip)

Appropriate Technology

        Although traditional land use is of great interest to us,
traditional back breaking work is less appealing! It is clear that we
cannot go back to traditional ways of working. In industrialised countries
a return to the highly labour intensive practices of the past is just not
conceivable from our economic viewpoint. However, it is possible that
efficient small-scale
technologies can enable the revival of industries based on traditional
forms of land-use.

(snip)

Hemp textiles in context

        The significance of hemp to the economic and day-to-day lives of
our ancestors is increasingly being recognised. It was important for
textile, paper, rope and oil production. Indeed, hemp was so important in
England in the sixteenth century that King Henry VIII passed an Act of
Parliament which
fined farmers who failed to grow the crop. Although hemp was mainly used to
produce ropes, sailcloth and sacking, the fabric which can be produced from
hemp is comfortable to wear, and this feature, combined with its
durability, meant that hemp was a fabric of choice for many working
clothes, often in blends with wool. It is interesting that Levi Strauss
made his first jeans from hempen cloth imported from Nimes in France, hence
the name "denim" which comes from "Serge de Nimes". Also, within living
memory Italian women
were wearing linen-like dresses made from hempen cloth which was sold in
all drapers shops in Italy (Bosticco, 1995).

(snip)

        Hemp, as a fibre crop is like flax (which is used to make linen).
Both hemp and flax fibres are known as 'bast fibres', that is the fibres
are contained in the stem. The processes and machinery required to produce
fabric are similar in principle for both crops. Whereas the hemp textile
industry has died out in the western world, the flax industry continues
with machinery
and expertise readily available.

        Hemp growing never ceased in France, and in response to concerns
about the narcotic uses of the hemp plant low narcotic strains were
developed. In recent years hemp has been grown in France to produce
cigarette paper and banknotes from the fibre and animal litter and bedding
material from the
woody core, also known as 'hurds'. Since 1993, hemp has once again been
grown in the UK under licence from the UK government. Hemcore, an Essex
based agricultural merchant successfully argued that under European
Community law, if the French could grow low narcotic hemp then why not UK
farmers? In 1995, 1,000 hectares of hemp were grown, 2,000 hectares are
being planted this Spring. Hemcore are growing hemp primarily to produce a
non-allergenic and absorbent horsebedding from the hurds. Some fibre is
being pulped to make tea-bags, cigarette papers and banknotes, but the
production of hemp textiles has proved more problematic.

        Growing consumer demand and interest in hemp fabric has stimulated
research in this area. The French have developed a chemical/enzymatic
process to produce a textile fibre which is awaiting funding for a pilot
plant (Matthieu,1994). In the UK Hemcore has been working with a textile
company to produce small quantities of hemp blended fabrics especially
using
recycled wool and cotton. We, at Bioregional Development Group, have been
working with Hemcore and other organisations to produce experimental
quantities of 100% hemp fabric.

        We believe hemp merits consideration as a new linen-like,
environmentally friendly, textile fabric. Hemp can be grown easily under
organic cultivation as it grows so fast that it smothers weeds. Indeed,
studies have shown that organically grown hemp has higher fibre yields
(Haraszky & Jakobey 1968) and improved fibre fineness (Jakobey 1968). In
addition, hemp is a multiple use crop. The high value, long "bast" fibres
are used to produce textiles, twine, geotextiles and paper. The shorter
"tow" fibres from textile processing are also suitable for geotextiles and
paper making. The woody
core or hurds are also fibrous and can be used for animal bedding, paper
making or in building materials, such as particleboard. The seed is used
for fish, bird or human consumption or for oil production. Growing regimes
vary according to whether seed or fine fibre is required. Obviously, aside
from the whole crop utilisation, multiple co-products will allow far
greater
income generation from the crop.

Bioregional Development Group's
"Hemp for Textiles" project

        In order to explore the value of UK gown hemp as a textile fibre we
instigated a project "Hemp for Textiles" with funding from the UK
Department of the Environment Local Projects Fund and the Konrad Zweig
Trust. Hemp for Textiles, which we have now almost concluded, aimed to:

   * grow four hemp varieties (in Kent in Southeast England) to explore any
differences in fibre quality and yield;
   * extract by different methods a textile grade fibre and produce samples
of UK hemp yarn and fabric;
   * compare processing techniques and evaluate the best way to establish a
UK hemp textile industry;
   * make our results available to interested parties and the
general public, to advance knowledge of hemp and its potential as a
sustainable crop.

The traditional method of producing hemp textiles

        As a starting point we investigated the centuries old method of
hemp textile production (Rowlandson, 1849; Eyre, 1913). In principle it is
similar to the method currently used to produce linen from flax. It
involved:

  1. sowing the seed densely to produce tall, slender stems which contain a
greater amount of finer fibre.
  2. harvesting after flowering but before the seeds set (the fibre content
is reduced and becomes coarser toward seed formation);
  3. "retting" the crop - retting (or rotting) being the name given to the
process whereby bacteria and fungi break down the pectins that bind the
fibres to the stem allowing fibre to be released; one of two alternative
methods were gen-erally used. Water retting, which involves lying the stems
in water in tanks, ponds or in streams for around 10 days -it is more
effective if the water is warm and bacteria laden; and/or dew retting,
which entails laying the crop on              the ground for 10-30 days,
turning as necessary to allow even retting;
  4. breaking the stems by passing through a "breaker" or fluted rollers.
  5. separating the fibre from the woody core ("scutching") by beating the
broken stems with a beech stick or passing through rotary blades, and
finally;
  6. "hackling" (combing) to remove any woody particles and to further
align the fibres into a continuous "sliver" for spinning. Spinning was
either carried out on a wet or dry basis. In the case of bast fibres
generally, the best yarns              are obtained by wet spinning
(Carter,1925), in which fibres are allowed to pass through a trough of hot
water before being spun. This softens the pectin allowing a greater drawing
out and separation of the fibres and producing a              finer yarn
(greater than 12Nm). Dry spinning is cheaper, producing yarns and fabrics
with a different appearance and handle.

Cultivation of hemp for textile production

        The first stage of our project was to grow hemp on a trial basis
specifically for textile fibre production. This we did in 1994 in Kent in
partnership with a Kentish farm, Hemcore (agricultural merchants) and Wye
Agricultural College, University of London. The seed was sown at a rate of
55kg/hectare on 11th May (for fibre production 55-60kg/hectare is
recommended -Franck, 1993). Four different low narcotic varieties were
grown, two French, F34 and F56 and two Hungarian, Kompolti and Uniko BF. We
saw for ourselves hemp's remarkable weed smothering properties and the crop
did not suffer from any pests. However, the crop did badly where the soil
was compacted by tractor wheels, with an obvious reduction in plant height
and increased competition from weeds along these "tram lines".

        We harvested the crop when the male plants were in flower and
shedding pollen and when the stems were whitening at the base and the
leaves were starting to drop as recommended in the literature (Rowlandson
1949, Eyre 1913). In our trial the French varieties were ready for harvest
on 7 August and the Hungarian varieties on 13 August (Uniko) and 27 August
(Kompolti).  The crop reached 1-2 metres in height. In our trial we found
that the Hungarian varieties yielded 70% greater biomass (as measured after
retting) than the French varieties.

        We also harvested 600 kg of Hemcore's 2 metre high commercial crop
on 24 August using an Allen Scythe, which laid the crop in an even swath.
The seed variety was F34, sown on 29 April.

Retting

        We chose dew retting as our main test method to produce enough
fibre for a spinning trial. After cutting, the hemp stems were laid
Parallel in rows to dew ret. The stems needed turning at least once
(sometimes twice) in order to allow for even retting. When turning, we
observed that the stems closest to the ground remained green whilst the top
was retting and turning brown. When retting was complete the crop was
entirely brown/grey. The thicker stems took longer to ret. Therefore
uniform tall, fine stems would seem to be best for trouble-free retting.

        Judging the degree and completeness of retting is currently a
subjective exercise based upon experience. Retting is complete when the
fibre bundles appear white, separate from the woody core and divide easily
into individual finer fibres for their full length. Evenness of retting is
as important as the degree of retting.

Table 1 Dew retting.

               hemp variety   harvest date    retting time
                F34 and F56      7/8/94            20 days
                 Uniko BF       13/8/94            22 days
                    F34         24/8/94            27 days
                 Kompolti        27/8/94      50 days (incompIete)

                       Water retting - 20 days at 4-5C

        For the earliest harvested crop, retting took only 20 days. For the
crop harvested 20 days later retting took 50 days and was incomplete (see
table1). This was due to a cold, wet spell of weather in September and
confirmed our suspicion that dew retting would prove risky in the UK
climate.

        Once it is considered that retting has gone far enough, the crop
needs to be dried to halt the retting process before it damages the fibre
and to prevent further retting in storage. With flax a moisture content of
less than16% is recommended. We stood the crop in stooks in the field to
dry, but turning and
then baling on a dry day would have the same effect.

        In our small-scale trials we harvested the crop by hand or with
small machines, but if hemp is to be farmed commercially for
textiles,special or adapted farm machinery will be needed to;

   * cut the crop and lay it in swaths,
   * turn the crop to allow even retting, and
   * bale the dried stems.

Extracting the fibre from the retted stems

        The next stop in our project was to investigate the ways in which a
fabric could be produced from the hemp we grew. With the resurgence of
interest in hemp fabrics, manufacturers of fibre extraction equipment,
research institutes, spinners and weavers have all been keen to run trial
batches on their machines.

        The amount of fibre contained within the stem is around 30% of
which perhaps 20% is suitable for textiles. For comparison, yields of flax
fibre from traditional scutching methods are 16-18% of long aligned fibre
for textiles and 8-10% short fibres (tow) from a similar total of 30% fibre
within the
retted stem (Sultana I991). lncidentally, the tow would be an excellent
paper making material.

We attempted fibre extraction by two different methods using;

   * conventional flax "scutching" machinery (producing aligned fibres)and
   * the new "Fibrelin" machine (producing nonaligned fibres)
developed in the UK to process flax.

        We sent retted stems to Depoortere, a flax processing machinery
manufacturer in Belgium for trial processing on a conventional flax scutch
line.The hemp stalks needed to be cut from their full length to 1.5 metres
and yields of only 8.5% fibre wore achieved (given that unadapted flax
machinery was used, with a scutch turbine adapted for hemp, we should be
able to obtain greater yields). To be processed on conventional flax
machinery, the stems have to be kept aligned throughout harvesting and
fibre extraction. The long aligned "hanks" of fibre thus produced will need
to be spun and woven on flax
machinery. A flax scutch machine adapted to take hemp could be produced and
indeed this is the method used in Eastern Europe to produce hemp fibre.
However, it is somewhat labour and energy intensive and requires that the
stems be aligned at all times.

        The remainder of the stems we sent to Silsoe Research Institute in
theUK to be processed through their new "Fibrelin" machine, The hemp was
successfully processed to produce nonaligned fibres, with a yield of 20-25%
fibre.  However, the hemp was very "heavy" on the machinery, which has been
designed for flax, and a rather more robust version of the machine would
need to be built to process hemp.

(snip)

Technical problems to be overcome

        We are pleased with the results of our experiment, as we succeeded
in producing the first machine processed, UK grown 100% hemp apparel fabric
probably this century. In the short term we feel that it would be possible
to establish hemp textile production in Southern England to produce high
quality hemp yarn and fabrics at a similar cost to linen. However, if
hemp is to be grown and processed in cooler climates or at a more
competitive price there are two technical problems which would need to be
overcome.

        Firstly, as hemp is harvested late in the season (a month later
than flax) dew retting of hemp is unreliable. Therefore we must develop
retting technologies that are suitable for our temperate climate, or bypass
the need to depend on the weather. A lot of work has been done on retting
flax, particularly by the French. In the UK we are also trying various
techniques but it is too early to asses their probability of success. A
great deal of work still needs to be done. What is certain is that unless
the problem of retting is overcome we will not be able to produce textiles
from hemp in countries where the climate is unsuitable for reliable dew
retting.

        The second problem is technically easier to overcome, but still
needs substantial research and development, After retting the hemp stems,
the fibre needs to be removed from the rest of the plant. As we have
discussed, adapted flax machinery can be used, but it is not entirely
suited to hemp which requires a more robust machine, and unless cutting the
stems in half as
we did for our trial is practiced, a much larger machine.  We believe that
the problem could be rapidly solved if the market demands the final
product.

(snip)

Potential Yields

        From the information that we have gathered we can calculate the
amount of fabric that could be produced from [an] earth tonne of hemp if it
were produced on a commercial scale.

        One tonne of hemp could comfortably be grown on 0.2
hectare(approximately 0.5 acre). A tonne of hemp would produce at
conservative yields of 15%, 150kg of line or high quality fibre. We should
expect losses of 35% in hackling or carding, 5% in yarn production and a
further 20% in boiling and bleaching the yarn to accept dye. This would
leave us with 73kg of fine hemp yarn producing 182 square metres of 400gsm
(jeans weight) fabric.

        In addition, 100kg (10%) of shorter tow fibres would be generated
which could be used for paper making or geotextiles and 500kg (50%) of hemp
hurds which would make excellent building materials or paper or can be sold
as animal bedding. Whole crop utilisation is obviously beneficial from both
an
economicand an environmental point of view.

Predicted conservative yields of fabric

0.2 hectares, (I tonne) hemp -> 150kg textile fibre -> 97.5kg sliver ->
73kg yarn -> 182 square metres of 400gsm fabric

In conclusion - Opportunities and challenges

        We learnt an enormous amount from our Hemp for Textiles trial. We
have written up the results along with details of hemp for textiles in UK
history and around the world in our report "Hemp for Textiles" (Riddlestone
et al, 1995).

(snip)

Sue Riddlestone - March 1996

References:
Bosticco, 1995 - Miss Mary Bosticco, personal communication
Carter,1925 - Modern flax, hemp and jute spinning and twisting (2ndedition)
Scott, Greenwood and Son, London.
Eyre, 1913 - Some Minor Farm Crops, Hemp, Journal of the Royal Agricultural
Society 1913, V74, pp 141-149.
Frank, 1993 - Cultivation of hemp, Translated from
FichesTechno-Economiques, Institut Agricole et Horticole Genech 1992
(French).
George, 1988 - A Fate worse than debt, Penguin.
Haraszyta A & Jakoby I, 1968 - Effects of trace elements on the harl
formation of hemp. Acta Biol. Debrcina 6:53-64 Field Crop abtracts, 23 3915
Jakobey,1968 - Effects of micro-elements and fertilisers on the fineness of
hemp. Rustnovenyek Kompolt 1968, 13-20 In; Field Crop abstracts, 22.
Mattheiu, 1994 - personal communication with Monsieur Mattheiu,Federation
Nationale des Producteurs de Chanvre (FNPC), Le Mans, France.
Rowlandson, 1849 - On Hemp, Journal of the Royal Agricultural Society
1849, v1O, pp172-182,
Riddlestone et Al, 1995 - Hemp for Textiles, growing our own
clothes,Bioregional Development Group, Sutton, Surrey UK.
Sale, 1991 - Dwellers in the land - the bioregional vision New
SocietyPublishers.
Sultana 1991 - La culture du lin fibre. Institut Technique Agrirole duLin,
France.
WCED, 1987 - Our Common Future, The World Commission on Environmentand
Development. Oxford University Press, Oxford.

Thanks to Dave Cull for sending us this.
E-mail: dcull at qb.island.net
WWW Site: http://fornits.com/no-zone/


Jack C. Thompson
Thompson Conservation Lab.
7549 N. Fenwick
Portland, OR  97217

503/735-3942  (voice/fax)

www.teleport.com/~tcl