Improvements in and connected with Retting or Steeping Flax and Hemp.
Year: 1895

page_text: Date of Application, 3rd Aug., 1895
Complete Specification Left, 2nd May, 1896-Accepted, 6th June, 1896
PROVISIONAL SPECIFICATION.
Improvements in and connected with Retting or Steeping Flax
and Hemp.
We, GEORGES LOPPENS and HONORÉ DESWARTE, of Nieuport, in the
Kingdom of Belgium, Manufacturers, do hereby declare the nature of this
invention to be as follows:-
This invention relates to the retting or steeping of flax and hemp in vats or
tanks by means of running water and has for object, to obtain, with a minimum
waste of water, an efficient process of retting flax and hemp by water which is
afterwards utilized for other purposes.
Retted flax or hemp, to be of value, must have undergone the necessary degree.
of normal fermentation by steeping in running water and must be uniform in
quality.
Regular fermentation effected by steeping in running water is distinguished by
the following characteristics,-
1. During the steeping; the particular odour which emanates from the flax under
treatment.
2. After steeping and drying; the peculiar fresh odour, the light yellow colour,
the fragility of the wood and the want of adherence of the fibre to the wood.
Amongst the processes in use at the present time that of steeping in running
water is the process which gives the best results.
The uniformity of the retted material depends entirely on the uniformity of the
same before the steeping, and also on the regularity of the steeping.
As is well known to practical men this uniformity is of the greatest importance
in the subsequent processes to which the material is subjected and to the value of
the product obtained.
From experiments based partly on the study of processes already known and
partly on numerous experiments which we have made we have found
A. That to bring about normal fermentation by steeping in running water it is
necessary that the juices extracted from the material under treatment shall not
remain in contact with the same but shall be replaced by fresh water in quantities
proportionate to the production of such juices.
B. That to obtain regularity in the steeping process it is necessary that the
water be renewed in all parts of the flax or hemp under treatment in the same way
and with the same facility.
Our invention consists
1. In forming and maintaining directly underneath the mass being steeped a
layer of fresh water which supplies the said mass with the necessary quantity of
water.
2. In ensuring that the whole of the material under treatment is supplied
regularly, uniformly and continuously with fresh water.
3. In drawing off the water containing the juices without mixing it with the fresh
water.
In carrying out our invention we employ vats or tanks with vertical sides and
provided with false bottoms arranged at a certain height above the bottom of the
tank. The inlet and outlet pipes for the water both enter the rats between the
bottoms and the false bottoms of the same, the inlet pipes however entering above
the level of the outlet pipes.

page_text: The flax or hemp is retained in the vats preferably by means of transverse boards
fixed in the vats.
The apparatus is employed as follows,-The bundles of flax (or hemp) are
arranged vertically on the false bottom of the vats in such a manner that the same
pressure exists throughout the whole mass.
The tops of the bundles are then covered with a layer of straw and the retaining
boards are arranged so as to keep the mass suitably immersed. The vats are then
filled with water and a current of water is allowed to flow through the same
the level of the water in the vat being kept approximately constant by regulating
the outlet.
The flax (or hemp) immersed has a tendency, varying with the degree of
fermentation, to rise in the water but is prevented from rising above a certain
height by the retaining boards.
The fresh water flowing into each vat spreads out in a layer under the bundles
of flax or hemp and is caused to rise through the bundles by the descending streams
of juice from the flax or hemp, the said juice being heavier than water. These
heavy streams slowly traverse the layer of fresh water and form in the bottom of
the same a layer of impure water which flows away through the outlet.
It is obvious that by this arrangement the retting, or steeping is effected: in a
regular and uniform manner.
Independently of the two essential requirements which are satisfied by our
process the latter presents other advantages which result from the peculiar manner
in which the circulation of the fluids takes place in the mass under treatment and
from the special arrangement adopted for the entrance and exit of the water into
and from the tank. Among such advantages are the following:-
a. The useful fibre is not wholly separated from the woody parts of the stems of
flax or hemp by the slow-circulation, which becomes slower as the extraction of the
juice from the flax or hemp diminishes. This separation frequently occurs in the
processes hitherto in use. Moreover when emptying the vat after the process of
steeping it is easy to effect the proper draining of the stems before removing the
bundles for the grassing process.
b. When the water flows too quickly into the vat the level of the lower
layer of impure water will sink until the outlet ceases to be quite covered
by this layer, in which case a certain quantity of fresh water will flow directly
through the vat without circulating in the mass under treatment, which will
continue to suck up a quantity of fresh water: sufficient to replace the juices
extracted from the same, that is to say, not only will an excess of water not be
prejudicial to the flax (or hemp) but such excess can be at once detected by. the
purity of the water which flows out from the vat and. can therefore be remedied.
c. When the fresh water does not flow quickly enough into the vat the diminution
in the circulation will be first'observable in the layer of impure water in the form
of abnormal fermentations (putrid, acid or butyric) before any effect. is produced
in the mass, where the water is always pure. The attendant will, then, be advised
by the odour of the water flowing from the outlet of the insufficiency of the flow of
water into the vat before injurious effects have been produced.
d. Lastly, on account of the slowness of the flow below the flax bundles and also
in the interstices in the same and on account of the superposition of the layers of
fresh and impure water, the said fresh and impure water will only mix to a slight
extent and the heavy juice will be: hardly diluted before it is drawn off through the
outlet. Except in the case in which the freshwater flows too rapidly, into the vat,
which it is easy to obviate, our process is attended with a minimum consumption
' of water as the latter only leaves: the vats when saturated more or less with the
juice extracted from the stems of the flax or hemp under treatment.
Dated the 3rd day of August 1895.

page_text: Improvements in and connected with Retting or Steeping Flax
and Hemp.
We, GEORGES LOPPENS and HONORÉ DESWARTE, of Nieuport, in the Kingdom
of Belgium, Manufacturers, do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to the retting or steeping of flax and hemp in vats or tanks
by means of running water and has for object to cbtain, with a minimum waste
of water, an efficient process of retting flax and hemp by water which is afterwards
utilized for other purposes.
Retted flax or hemp, in order to be of the greatest value, must have undergone
to the necessary degree the special fermentation which is obtained by steeping in
running water; it must also be as uniform as possible.
Regular fermentation such as that effected by steeping in running water is
distinguished by the following characteristics
:-
1. During the steeping; the particular odour which emanates from the flax or
hemp:
2. After steeping and drying; the peculiar fresh odour, the light yellow colour,
the fragility of the wood and the very slight adherence of the fibre to the-
wood.
The uniformity of the retted material necessitates evidently the uniformity of
the straw before the steeping and requires the steeping to be carried on with.
regularity.
As is well known to practical men, the uniformity of retted material is of the
greatest importance having regard to facility in stripping and to the value of
the harl.
From thorough researches, based partly on the study of processes already known
and partly on numerous experiments which we have made, we have ascertained :-
A. That to bring about normal fermentation by steeping in running water, it is.
necessary and sufficient that the juices extracted from the material under
treatment do not remain in contact with the same and that they be replaced
by fresh water in proportion as they are produced.
B. That to obtain the greatest possible regularity in the steeping it is necessary
and sufficient that the water be renewed in all parts of the retting straw in the
same way and with the same facility.
.
Our invention relates to a steeping process in tanks or vats by which these
objects are attained together with a great saving in water and it consists: -
1. In forming and maintaining directly underneath the material being steeped
a layer of fresh water which supplies it with the necessary quantity of water.
2. In ensuring that the material under treatment is supplied with fresh water
regularly, uniformly and constantly throughout its whole mass.
3. In collecting and drawing off the water containing the juices without mixing
it with the fresh water.
In carrying out our invention, we employ a tank or vat having vertical sides and
provided with a false bottom with openings. The inlet and outlet pipes for the
water both enter the tank between the bottom and the false bottom, the first
entering at a higher level than the second. They must be large enough to allow
the water to pass in and out without producing eddies or whills.
The flax or hemp is retained in the water preferably by means of boards or slats
secured by bars fixed by pins passing into uprights in each tank or by other
suitable means.

page_text: The flax or hemp is worked up into double bundles that are made of two ordinary
bundles placed head to foot and having consequently a nearly cylindrical form.
These bundles are arranged vertically on the false bottom of the tank in such a
manner that the stems are subjected to a like pressure throughout the whole mass.
The tops of the bundles are then covered with a layer of straw and the retaining
slats are arranged so as to keep the mass suitably immersed. The tank is then
filled with water and the renewal of the water is regulated in such a manner as to
keep its level approximately constant.
The flax (or hemp) immersed has a tendency, varying with the degree of
fermentation, to rise in the water but is prevented from rising above a certain
height by the retaining boards or slats.
The fresh water flowing into the tank spreads out in a layer under the
bundles. From this layer, slender streams of fresh water ascend on all sides into
the interstices of the stems, and replace therein the descending streams of juice,
the said juice being heavier than water. These impure heavy streams slowly
traverse the layer of fresh water and form in the bottom of the tank a layer of
impure water which flows away through the outlet.
We will now point out how our process satisfies the condition herein before
mentioned.
The presence of a layer of fresh water bathing the lower parts of the stacks
ensures that the juices set free from the mass under treatment are replaced by a
tream of fresh water and this takes place without any hindrance on account of
great velocity with which the water can circulate in the interstices between the
fib these interstices forming veritable small continuous canals along the whole
leng height of the stacks or bundles.
L
Fron
has been stated it will be understood that, provided the stalks or
stems are uniformly packed throughout the tank, the renewal of the water is
effected in all parts of the material in the same way and with the same facility.
Independently of the two essential requirements which are satisfied by our
process the latter presents other advantages which result from the peculiar manner
in which the circulation of the fluids takes place in the mass under treatment and
from the special arrangement adopted for the entrance and exit of the water into
and from the tank. The very gentle circulation of the water and its decrease
as the production of the soluble juices diminishes gives rise to the following
advantages:-
:-
a. The fibres are prevented from being entirely deprived of their gummy
substance as is the case at the end of ordinary retting processes in which the
gummy substance which should remain in the fibres becomes reduced to a very soft
mucilaginous condition and is easily separated by a too rapid circulation of water
or rubbing of any kind. Moreover, by completely emptying the tank after the
process of steeping it is easy to effect the proper draining and hardening of the
stems before removing the bundles for the grassing process. This precaution
absolutely prevents the production of white veins resulting, in river retting, from
the rough handling to which the wet stems are subjected when unloading them.
b. When the water flows too quickly into the tank the level of the lower layer
of impure water will sink until the outlet ceases to be quite covered by this layer,
in which case a certain quantity of fresh water will flow directly through the tank
without circulating in the mass under treatment, which will continue to suck up
from the layer of fresh water a quantity sufficient to replace the juices extracted
from the same, that is to say, not only will an excess of fresh water not be pre-
judicial to the flax (or hemp) but such excess can be at once detected by the purity
of the water which flows out from the tank and can therefore be remedied.
c. When the fresh water does not flow quickly enough into the tank, the
diminution in the circulation will be first observable in the layer of impure water
in the form of abnormal fermentations (putrid, acid or butyric) before any effect
is produced in the mass, where the water is always purer. The attendant will,
then, be warned, by the odour of the water flowing from the outlet, of the

page_text: insufficiency of the flow of water into the tank before injurious effects have been
produced.
d. Lastly, on account of the low velocity of the flow below the flax bundles and
also in the interstices in the same and on account of the superposition of the layers
of fresh and impure water, the said fresh and impure water will only mix to a slight
extent and the heavy juice will be hardly diluted before it is drawn off through
the outlet. Except in the case in which the fresh water flows too rapidly into the
tank, which it is easy to obviate, our process is attended with a minimuin con-
sumption of water as the latter only leaves the tank when more or less saturated
with the juice extracted from the stems of the flax or hemp under treatment.
In the accompanying drawing which represents a vertical section of a tank or
vat for retting or steeping flax in accordance with our invention,―
A is the layer of pure water fed into the tank through the passage B which
allows the water to rise to the required height.
C is the layer of impure water flowing off through the outlet passage D, the
flow being regulated by the sluice I. Or the outlet passage D may be extended
up to near the top of the tank and the outflow be regulated by an adjustable over-
flow aperture. In this case a suitable valve would be placed in the bottom of the
tank for emptying it after each operation.
M is the mass under treatment which rests on the perforated false bottom E but
which is lifted under the pressure of the water when the level is sufficiently high
in the tank.
F, F are the boards or slats resting on a layer of straw f covering the material
which is being steeped.
G is one of the securing bars placed on the slats F and held by pins passed into
holes in the uprights H.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The herein before described process of retting or steeping flax and hemp, such
process consisting in causing fresh water to circulate vertically through the bundles
of flax or hemp and quite uniformly through every part of the mass: the said
circulation being caused solely by the superior density of the juice given out by
the stems, which descends and causes an upward flow of fresh water.
2. For carrying out the method of circulation referred to in Claim 1 with a
minimum supply of water, maintaining a free space of sufficient height between the
bottom of the tank and the mass of flax and hemp under treatment and arranging
the water inlet aperture at the top and the outlet aperture at the bottom of the
said space so as to maintain a layer of fresh water between the bottom of the mass
and the layer of impure water which forms in the bottom of the tank, substantially
as herein before described.
3. The improved apparatus for use in retting or steeping flax and hemp
herein before described and illustrated in the accompanying drawing.
Dated the 2nd day of May 1896.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.