Improvements in and Connected with Indigo Dyeing.
Year: 1888

page_text: Date of Application, 27th Dec., 1888
Complete Specification Left, 25th Oct., 1889-Accepted, 23rd Nov., 1889
PROVISIONAL SPECIFICATION.
Improvements in and Connected with Indigo Dyeing.
I, JAMES COWAN, of the firm of Cowan & Drysdale, Drysalters, of 124 Renfield
Street, Glasgow, Lanarkshire, do hereby declare the nature of my invention to be as
follows:-
This Invention has reference to the dyeing with real Indigo or Indigo Blues of
wool and woollen goods and other fibrous materials, such as silk, cotton, linen, or jute,
and of yarns or thread, or other textile or woven fabrics or piece goods, and of other
substances or marketable materials; and comprises certain new or improved mixtures,
combinations, or compounds of substances with pure commercial Indigo, for use as
new or improved basic or solvent compounds in preparing or making down with
water the deoxidised Indigo liquid dye vats in the said dyeing process; including
improvements in the mode and means of preparing these new compounds; and also
improvements in the process of dyeing therewith all of which improvements will
save much time and labour, besides being more economical, convenient, and
advantageous, as compared with the modes and means heretofore employed in such
pure Indigo dyeing.
The nature and novelty of the improvements of this invention consist all as
follows: Namely, as regards one example of the first or dry new or improved
Compound (which is susceptible of modification as hereinafter described) this consists
of the following substances in nearly the proportions here given :-
Pure Commercial Indigo, ground to powder
Zinc Oxide or Zinc Powder
West Indian or other Sugar in Crystals
Potassium Carbonate
-
100 parts by weight.
100
"
"
"
40 "
""
"
20 "
"
"
These ingredients would be thoroughly mixed and ground together, preferably in a
fine grinding or disintegrating mill, along with the Indigo, the latter being preferably
previously ground to an impalpable powder, all in a dry state. This dry powdered
mixture thus prepared by the first improvement is ready for being made up in
parcels by weight for use or sale as a new dry basic Dyeing Compound. In using
this new compound or prepared Indigo powder it is first put into a tub or vessel and
water, either cold or warin added, and the whole mixture is then stirred until it
becomes a thin paste or liquor. To this is added 20 parts by weight of sulphuric
acid at about 166 degrees Twaddel, (commercially known as oil of vitriol) and
stirred; and thereafter the whole mixture put into a dye vat of hot water preferably
about 180° Fahrenheit, and thoroughly stirred. To this liquor in the dye vat is
added 450 parts by weight of liquid Bisulphite of Soda, and after stirring, the Indigo
in the dye vat will be deoxidised or reduced and rendered soluble, ready for
commencing dyeing operations.
Instead of mixing the sulphuric acid, and the bisulphite of soda, with the prepared
Indigo compound, at separate operations, the sulphuric acid and bisulphite of soda
may be mixed together in presence of water either hot or cold, and the Indigo dry
compound then added and thoroughly mixed with them in the dye vat.
As an alternative to preparing the Indigo new compound, as a dry powder, by a
further improvement I prepare it in the form of a solution or liquid solvent
compound, with the ingredients hereinafter stated, which on being added to a hot or
boiling dye vat of water, will at once on stirring or mixing the dye liquor, give to
the dyer a deoxidised Indigo liquor vat ready for instant use.

page_text: Sulphuric Acid at 166° Twaddel
Water, either hot or cold
Liquid Bisulphite of Soda
-
-
20
1,300
450
These substances on being stirred and thoroughly mixed together, form the Indigo
new Liquid Compound, ready for being placed in casks to be conveyed to the dye
vats for use as a deoxidising Indigo liquor.
Instead of the Potassium Carbonate salt used in the aforesaid dry or liquid
compounds or mixtures for rendering Indigo soluble, other equivalent salts can be
substituted therefor, such as Potassium Bicarbonate, Nitrate or Chlorate, Sodium
Oxide, Carbonate, Bicarbonate or Soda Ash, or Nitrate or Biborate, and which will
give corresponding results and not be precipitated at the temperatures maintained in
the dye Vats. And instead of West Indian Sugar, other sugars may be used, such
as beetroot, grape, or milk sugar, honeys, sugar syrups, or molasses, or the saccharine
matter may be taken from other substances. And instead of sulphuric acid, Hydro-
sulphurous or equivalent acid may be used.
The die vat prepared as described would have the Indigo so strong and thoroughly
deoxidised that the vat can be kept at any desired high temperature up to boiling
and at any degree of concentration, according to the shade of blue desired by the
dyer, which would enable the material to be dyed very quickly, or by a very short
immersion in the vat, in fact effecting this in as many minutes as hours were here-
tofore required in the Indigo vats containing lime or lime salts for the deoxidation of
the Indigo, and which required special treatment at low temperatures to prevent
lime being precipitated on and damaging the articles being dyed.
By these improvements a vat dye liquor ready for immediate use is at once
obtained, instead of after lengthened and troublesome operations to attain the same
end by existing methods. Continuous dyeing may proceed in same vat, no rests or
intervals (in some cases of considerable duration) requiring to take place between
each dyeing as is the case with existing processes. Nor is any delay occasioned by
the addition of dyeing ingredients to the dye vat, as, immediately after stirring up,
dyeing can proceed, whereas under the present processes, a lengthened rest for the
dye liquor is required every time dye stuffs and particularly lime are added. There
being no lime used in this process, or in the preparation of the prepared Indigo
powder, the dye liquor can be stirred up at any time the dyer chooses, without
injuring either the dye liquor or goods immersed in it, whereas, the presence of lime
in most existing processes (both for reducing or rendering Indigo soluble, and in the
subsequent dyeing operation itself) prevents even the slightest stirring being done,
and renders those "rests" just described of absolute importance, so as to allow the
lime to settle at the bottom of the dye vat. For the same reason, namely, the presence
of lime in the Indigo solution used or to render it soluble in vat, and the necessity of
its frequent addition to dye liquor besides, under existing processes, the dyeing heat
has hitherto been restricted, of necessity, to a heat of about 145° Fahrenheit as a
maximum, and to about 118° or 120° as a usual working heat, whereas in the present
new process, a very high heat can be employed, extending for certain materials even
to boiling, and to 160° or thereby, in the case of cotton, linen, or jute, for which
Indigo dyeing is generally conducted cold, because of the great quantity of lime

page_text: present in dye vat. The possibility of using such high heats in dyeing by my new
process, assures an immensely augmented daily output of dyed material, whether
one vat or many may be employed. No special plant or fittings are required for my
new process, unlike previous methods, which from the nature of the dyeing compounds
employed, and the consequent danger of injurious sediments being disturbed by the
direct introduction of steam to the dye liquor in frequent cases necessitates a special
and expensive adaptation of dye vats, so as to overcome this drawback.
These improvements would be carried into practice in the operations of dyeing, as
follows: In the case of unspun wool (previously scoured and washed) dyeing can
begin at a heat of 180° Fahrenheit, which heat may be raised to boiling, if desired,
and dyeing continued and completed at that temperature. In the case of yarns or
goods dyed in cloth or piece, the dye liquor should be cooled before dyeing begins
to 130° Fahrenheit, or thereby, and the goods (previously properly scoured and wet
out) may then be entered in the dye liquor, and worked in the usual way, either in
one continuous operation till the desired shade is got, or by successive dips or runs
with the customary squeezing and airing between each, in dyer's option. As dyeing
proceeds, the heat may be raised from 130° Fahrenheit to boiling, the reason for
starting at 130°, for yarn and piece goods being, that more uniform shades of colour
are thus got, this course not being important in the case of wool, which, even at the
high heats already stated, is dyed sufficiently uniform in shade for practical purposes,
as any slight irregular or uneven dyeing which may appear when dyeing is done, is
remedied in the subsequent carding process which dyed wool must undergo before it
can be spun into yarn.
The quantities of prepared Indigo powder, oil of vitriol, and bisulphite of soda to
be used in dyeing a given shade of blue must necessarily be regulated by the intensity
or depth of the shade desired, but, as an example of a practical dyeing operation,
the following directions are given to obtain on 200 lbs. of unspun wool (previously
scoured and washed) an ordinary blue shade. Enter in hot or boiling water, in a
dye vat of a capacity suited to the quantity of wool above named, 65 lbs. of the
prepared new Indigo powder, and 10 lbs. Oil of Vitriol, both articles having been
previously mixed in a tub as already instructed, then add 112 lbs. liquid bisulphite of
soda and stir well. Or instead of the aforesaid a corresponding quantity of the new
liquid Indigo Compound may be taken. The Indigo will immediately become soluble,
and after cooling the dye liquor with cold water to 180° Fahrenheit (if boiling heat
has been used in preparing the vat liquor) the wool may be entered in the usual way,
and as much as possible kopt under the surface of the dye liquor. When sufficiently
dyed, raise and squeeze the wool, letting surplus liquor drain into the dye vat, then
open out the wool as well as possible, so as to let the air act on it freely, and as
uniformly as may be, when, from a yellowish, olive green, the colour on the wool
will change by the oxidation of the air, to a rich, full shade of blue. After cooling
and airing, the usual subsequent process of washing and cleaning may be proceeded
with. For a second batch of wool of equal weight, and of same-shade, dyeing may
at once be resumed in same dye liquor, (first stirring it well up), and without any
further addition of dyeing ingredients; but in that case a longer time will be taken
to obtain an equally full shade of blue, for the reason that the dye liquor is necessarily
weaker than at first. In practice, however, this course will rarely be taken, unless
for the dyeing of light shades, and the dyer will prefer in doing a series of dyeings
of same weight and shade, to add for each fresh dyeing operation one half the
quantity of prepared dry Indigo powder, oil of vitriol, and bisulphite of soda, or a
corresponding quantity of the new liquid Indigo Compound, which he used for
dyeing the first or starting lot. This course permits of the shade being arrived at
much more rapidly, and as a consequence, a much increased daily output of dyed
material is assured. Practically the same directions will apply to the dyeing of
woollen yarns or piece goods, due allowance being made for the difference of
working these, whether mechanically or by hand, as distinguished in usual practice
from the dyeing of wool, and for the difference of dyeing heat recommended at start
for the reason already given. Silk dyeing would be conducted on the same lines, thë

page_text: material first being prepared for dyeing in the customary way. Cotton and linen
goods would be dyed without any special preparation, and would be simply thoroughly
wet out before dyeing commences, and be dyed in a dye liquor prepared exactly as
described for wool, but dyeing should not be conducted at a heat of over 160°.
Practical Indigo dyers will understand these facts, as detailed, and see in them
important improvements on existing methods or processes, whether for reducing the
Indigo to a soluble state in the dye vat, or in the simplicity, rapidity, and economy
of time and plant in the dyeing operations themselves.
Dated the 26th December 1888S
W. R. M. THOMSON & Co.,
A gents
:
COMPLETE SPECIFICATION.
Improvements in and Connected with Indigo Dyeing.
1, JAMES COWAN, of the firm of Cowan & Drysdale, Drysalters, of 124 Renfield
Street, Glasgow, Lanarkshire, do hereby declare the nature of my said Invention,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement in writing, that is to say :-
This Invention has reference to the dyeing with real indigo or indigo blues of
wool and woollen goods and other fibrous materials, such as silk, cotton, linen, or
jute, and of yarns or thread, or other textile or woven fabrics or piece goods, and of
other substances or marketable materials; and comprises certain new or improved
mixtures, combinations, or compounds of substances with pure commercial indigo,
for use as new or improved basic or solvent compounds in preparing or making
down with water the deoxidised indigo liquid dye vats in the said dyeing process;
including improvements in the mode and means of preparing these new compounds;
and also improvements in the process of dyeing therewith; all of which improvements
will save much time and labour, besides being more economical, convenient, and
advantageous, as compared with the modes and means heretofore employed in such
pure indigo dyeing.
:-
The nature and novelty of the improvements of this invention consist all as
follows Namely as regards one example of the first or dry new or improved
compound (which is susceptible of modification as hereinafter described) this consists
of the following substances in or near the proportions here given :-
Pure Commercial Indigo, ground to powder
Zinc Oxide or Zinc Powder
West Indian or other Sugar
Potassium Carbonate
100 parts by weight.
100
"
"
"
40
23 "
"
20
33
""
"
These ingredients would be thoroughly mixed and ground together, preferably in a
fine grinding or disintegrating mill, along with the Indigo, the latter being preferably
previously ground to an impalpable powder, all in a dry state. This dry powdered
mixture thus prepared by the first improvement is ready for being made up in
parcels by weight for use or sale as a new dry basic dyeing compound. In using
this new compound or prepared indigo powder, to make up a dyeing liquor vat, it is
first put into a tub, pail, or other vessel, along with hot water, and to this is added
and stirred an equal weight of liquid Bisulphite of Soda, and this mixture is then
added to a dye vat of hot or boiling water and the whole boiled for a few minutes.
Or alternatively, a dye liquor vat may be prepared by adding equal proportions by
weight of the prepared Indigo powder and liquid Bisulphite of soda direct to a dye
vat of hot or boiling water without previous mixture. The Indigo in the dye vat has
meantime become deoxidised or reduced and rendered soluble, and dyeing operations
may commence after a few minutes have been allowed to let the dye liquor settle,

page_text: dyeing being better conducted in the clear liquor. Alternatively a stock vat may be
employed prepared as just described in any desired concentration by the addition to
equal proportions by weight of prepared indigo powder and bi-sulphite of soda of
more or less water, and the whole boiled up for a few minutes. This would form a
stock supply from which the dye vat could be fed as required, such stock liquor or
solution only requiring to be stirred ere any portion of it is added to the dye vat,
which would at once be available for use after the few minutes allowance for liquor
to settle.
As an alternative to preparing the indigo new compound, as a dry powder, by a
further improvement I prepare it in the form of a solution or liquid solvent compound,
with the ingredients hereinafter stated, which on being added to a hot or boiling dye
vat of water will, on being boiled for a few minutes and allowed a brief time to
settle, give to the dyer a clear deoxidised Indigo liquor vat ready for instant use.
INGREDIENTS OF INDIGO NEW LIQUID COMPOUND.
Of this mixture I take one part by weight, and of liquid Bisulphite of Soda one
part by weight, and water either hot or cold in quantity according to concentration
desired.
As regards the use of sulphuric acid with my prepared Indigo powder or new
liquid solvent Indigo compound, as set forth in my provisional specification, further
experiments have shown that its use is not essential, and in practice, may be
discontinued in dyer's option, without detriment to dyeing results, unless when the
liquid bisulphite of soda employed has become deficient in sulphurous acid, when an
addition to dye vat of sulphuric acid in or near the proportion stated in my said
provisional specification may be made with advantage, to renew or restore the effective
action of the bisulphite of soda on the zinc present in the dye vat. To effect the
same object and as an equivalent for sulphuric acid, liquid sulphurous acid may be
employed instead.
These substances on being stirred and thoroughly mixed together form the Indigo
new liquid compound ready for being placed in casks to be conveyed, after first being
well stirred, to the dye vats for use as a deoxidising Indigo liquor in the way already
described for the use of the dry prepared Indigo powder and bi-sulphite of soda.
Instead of the Potassium Carbonate salt used in the aforesaid dry or liquid
compound or mixture for rendering Indigo soluble, other equivalent salts can be
substituted therefor, such as Potassium Bicarbonate or Potassium oxide, sodium
Oxide, Carbonate, Bicarbonate, Nitrate, Biborate, or Soda Ash. And instead of
West Indian sugar, other sugars may be used, such as beetroot, grape, or milk sugar,
honeys, sugar syrups, or molasses, or the saccharine matter may be taken from other
substances. The dye vat prepared as described would have the Indigo so thoroughly
deoxidised that the vat can be kept at any desired high temperature up to boiling
and at any degree of concentration, according to the shade of blue desired by the
dyer, which would enable the material to be dyed very quickly, or by a very short
immersion in the vat.
By these improvements a vat dye liquor ready for immediate use is obtained,
instead of after lengthened and troublesome operations to attain the same end by
existing methods. Continuous dyeing may proceed in same vat, no rests or intervals
extending to from one to two hours requiring to take place between each dyeing as

page_text: For the
is the case with existing processes. Nor is any delay occasioned by the addition of
dyeing ingredients to the dye vat, as immediately after stirring up, and settling for
a few minutes dyeing can proceed, whereas under all previous processes, a lengthened
rest for the dye liquor is required every time dye stuffs and particularly lime are
added. There being no lime used in this process, or in the preparations of the
prepared Indigo powder or new Indigo liquid solvent compound the dye liquor can
be stirred up at any time the dyer chooses, without injuring either the dye liquor or
goods immersed in it, whereas the presence of lime in most existing processes (both
for reducing or rendering Indigo soluble, and in the subsequent dyeing operation
itself) prevents even the slightest stirring being done after that which is given when
it is added at first, and renders those "rests" just described of absolute importance,
so as to allow the lime thoroughly to settle at the bottom of the dye vat.
same reason, namely, the presence of lime in the Indigo solution used or to render
it soluble in vat, and the necessity of its frequent addition to dye liquor besides,
under existing processes the dyeing heat has hitherto been restricted, of necessity, to
a heat of about 145° Fahrenheit as a maximum, and to about 110° to 120° as a
usual working heat for wool and woollen goods, whereas in. the present new process
a very high heat can be safely and indeed advantageously employed, extending for
certain woollen materials even to boiling point and to 160° or thereby, in the case
of cotton, linen, or jute, for which Indigo dyeing is generally hitherto conducted
cold, because of the great quantity of lime present in dye vat. The possibility
besides of using such high heats in dyeing by my new process, assures an immensely
augmented daily output of dyed material, whether one vat or many may be employed.
No special plant or fittings are required for my new mixtures and process, though
preferably I advise the use of Iron or Zine dye vats heated by a fire or by indirect
steam heat applied by means of dumb or unperforated pipes or an outer shell or
steam jacket.
:-
These improvements are carried into practice in the operations of dyeing as
follows In the case of unspun wool (previously scoured and washed) dyeing can
begin at a heat of 180° Fahrenheit, which heat may be increased to 200° Fahrenheit,
or thereby if desired, and dyeing may be continued and completed at that temperature.
In the case of yarns, or goods dyed in cloth or piece, the dye liquor should be
cooled before dyeing begins to from 150° to 160° Fahrenheit or thereby for yarns,
and 170° Fahrenheit or thereby for woollen piece goods, and the goods (previously
properly scoured and "wet out") may then be entered in the dye liquor, and
worked in the usual way, either in one continuous operation till the desired shade is
got, or in dyers option by successive dips or runs with the customary squeezing and
airing between each. As dyeing proceeds, the heat may be raised for piece goods to
just off boil if desired, and dyeing process may be completed at that heat. The
reason for starting at a less heat for yarns and piece goods than for unspun wool,
being that more uniform shades of colour are thus got, this precaution not being so
necessary in the case of wool, which even at the high heats already stated, is dyed
sufficiently uniform in shade for practical purposes, as any slight irregular or uneven
dyeing which may appear when dyeing is done, is remedied in the subsequent
carding process which dyed wool must undergo before it can be spun into yarn.
The quantities of prepared Indigo powder, and bisulphite of soda to be used in
dyeing a given shade of blue or of the new Indigo liquid solvent compound must
necessarily be regulated by the intensity or depth of the shade desired, but, as an
example of a practical dyeing operation, the following directions are given to obtain
on 200 lbs. of unspun wool (previously scoured and washed) a good deep blue shade.
Enter in hot or boiling water in a dye vat of a capacity suited to the quantity of
wool above named, 65 lbs. of the prepared new Indigo powder, and 65 lbs. liquid
Bisulphite of soda, both articles having been previously mixed to a paste in a tub
with water as already instructed and boil for a few minutes. Or instead of the
aforesaid a corresponding quantity of the new liquid Indigo Compound may be
taken. After boiling for a few minutes the Indigo will have become soluble and
after dye liquor is allowed 5 or 10 minutes to clear the wool previously "wet-out" in

page_text: hot water, may be entered into dye vat in a net in the usual way, and as much as
possible kept under the surface of the dye liquor. When sufficiently dyed, raise and
squeeze the wool, letting surplus liquor drain into the dye vat, which is not run off,
but retained for further use, then open out the wool as well as possible, so as to let
the air act on it freely, and as uniformily as may be, when, from a yellowish green,
the colour on the wool will change by the oxidation of the air, to a full shade of
blue. After cooling and airing, the usual subsequent process of washing may be
proceeded with. For a second batch of wood of equal weight, and for same shade,
dyeing may at once be resumed in same dye liquor, (first stirring it well up, then
letting it settle for a few minutes), and without any further addition of dyeing
ingredients; but in that case a longer time will be taken to obtain an equally full
shade of blue, for the reason that the dye liquor is necessarily weaker than at first.
In practice, however, this course will rarely be taken, unless for the dyeing of light
shades, and the dyer will prefer in dyeing a series of dyeings of same weight and
shade to add to the retained dye liquor of first dyeing for each fresh dyeing operation
one half the quantity or thereby of prepared dry Indigo powder, and bisulphite of
soda, or a corresponding quantity of the new liquid Indigo Compound, which he used
for dying the first or starting lot. This course permits of the shade being arrived at
much more rapidly, and as a consequence, a much increased daily output of dyeing
material is assured. Practically the same directions will apply to the dyeing of
woollen yarns or piece goods, due allowance being made for the difference of working
these, whether mechanically or by hand, as distinguished in usual practice from the
dyeing of wool, and for the difference of dyeing heat recommended at start for the
reason already given, and according to strength of dye liquor any desired shade can
be arrived at in one or several dips or dyeing operations in dyer's option, squeezing
and airing being always duly attended to, and such goods are thereafter washed and
cleaned in the usual ways. Silk dyeing would be conducted on the same lines, but
in a more concentrated vat liquor the material first being prepared for dyeing in the
customary way. Cotton and linen goods would be dyed without any special
preparation, and would be simply thoroughly boiled or "wet out" before dyeing
commences, and he dyed in a dye liquor prepared exactly as described for wool, but
in a more concentrated form, and dyeing should not be conducted at a heat of over
150° Fahrenheit.
In the case of cotton warps, desired shade can be got in one vat and in one dyeing
operation instead of requiring to pass through a series of vats of different degrees of
strength and at a great expenditure of time as at present and hank yarns can also bo
dyed in one vat and in one or more dyeing operations in dyer's option.
The fact of cotton being dyed hot by my process renders the Blues so produced
faster to soaping than those obtained by the existing cold processes.
For the same
reason they are also cleaner, stand bleaching better, and have the important further
advantage over Blues done by old methods when woven into white linen goods, of
enabling them to be calendered direct from the loom without marking off or staining
the white part of said goods, thus obviating the use of cotton sheets between the
folds which at present is necessary on account of the existing Indigo Blues having
the serious defect of marking or staining white in the process of calendering unless so
protected, and thus causing great extra expense on the cost of production of such
linen goods for the market, all which is saved by the adoption of my process.
Practical Indigo dyers will understand these facts as detailed, and see in them
important improvements on existing methods or processes, whether for reducing the
Indigo to a soluble state in the dye vat, or in the simplicity, rapidity and economy of
time and plant in the subsequent dyeing operations.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is.-
First. The use of the herein described new dry basic Indigo dyeing compound for
the purposes set forth.

page_text: Second. The use of the herein described new liquid Indigo dyeing compound for
the purposes set forth.
Third. A dry Indigo compound or mixture for Indigo dyeing having Potassium
Carbonate, or the other herein described equivalent substances, substantially as
set forth.
Fourth. In liquid Indigo compounds or mixtures for Indigo dyeing, the use of
Potassium Carbonate or the other herein described equivalent substances, substantially
as set forth.
Fifth. The mode and means of mixing and preparing the dry and the liquid
Indigo compounds as described and distinguished for use in Dyeing, substantially as
set forth.
Sixth. The herein described process or mode and means of mixing and preparing
the liquid vats from the dry and the liquid new Indigo compounds for the dyeing of
different goods, substantially as set forth.
1009
W. R. M. THOMSON & Co.,
96, Buchanan Street, Glasgow, Agents.