Improvements in the Manufacture of. Black. Tea.from the Green Tea Leaf, and a New Compound for Use in such Manufacture.
Year: 1899

page_text: PROVISIONAL FEUIFICATION
14-
I
Improvements in the Manufacture of. Black. Tea.from the Green Tea
Leaf, and a New Compound for Use in such Manufacture.
JA
t
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ireland,
Merchant, do hereby declare the nature of this invention to be as follows:-
My invention relates to the treatment of tea leaf in the course of its manu-
facture into what is commercially known as black tea, and it consists of an
improvement in the treatment of the leaf and also of a new compound for use in
such treatment.
In the manufacture of tea leaf into black tea, according to the method hitherto
ordinarily followed the leaf is first withered, then rolled, after which, and while
still in a moist state, it undergoes a process of oxidation which is generally
known as fermentation," during which absorbs oxygen, whereby it loses its
"
green colour and becomes a brownish tint.
The successful accomplishment of the changes which are effected in the leaf,
by its proper absorption of oxygen, determines to an important extent the subse-
quent quality of the tea, after its manufacture has been completed by the final
drying of the leaf.
...!
If the condition of the leaf and the nature of its juices, when it is being manu-
factured, are such that a long continuance of the fermentation process is required,
in order to effect the requisite absorption of oxygen and other necessary changes
for the production of black tea, the quality of the liquor obtained by infusing
the finished tea (hereinafter referred to as the infusion) is depreciated, owing
to the fact that a long duration of the fermentation process also involves further
changes taking place in the leaf and juices of a detrimental nature, which render
their albuminoid constituents less soluble in the infusion and which at the same
time materially reduce the pungency and strength of the infusion.
Accordingly the object of my present invention is to so treat the leaf after it has
been withered, and while it is being subsequently rolled, that its tendency to
absorb oxygen is enhanced, whereby the duration of the process is greatly
curtailed, the said absorption more advantageously effected, the originally con-
tained pungency and strength of the leaf and juices more fully preserved, and
the solubility of the albuminoid constituents increased, so that the resulting
black tea produces a richer coloured and stronger infusion, and is of improved
market value.
My invention consists in adding to the leaf, after it has undergone the above
referred to withering process, and during the subsequent rolling operation,
approximately one-half to one per cent. of its weight of a compound, consisting
of ordinary sugar ground into a fine powder, with an alkaline substance, such as
the carbonate or bi-carbonate of soda, potash or magnesia, or an admixture thereof
(hereinafter referred to as the alkali) in the proportion of preferably three parts
of sugar to one part of the alkali (and which combination of sugar and alkali is

page_text: hereinafter referred to as the compound); but I do not limit myself to the
particular proportions of sugar and alkali herein stated, or to any exact per-
centage of the compound which may be applied to the leaf, as the quantity may
be varied to suit special growths of the tea leaf, but the proportions and percentage
above stated answer well in ordinary cases.
The incorporation of the compound into the leaf is conveniently effected by
sifting it gradually over the same while it is undergoing the rolling operation,
and preferably after the surfaces of the leaf have become slightly moistened by
the exuding juices, after which the further squeezing and turning over and over
to which the leaf is subjected before its rolling is completed, very thoroughly
mixes and incorporates the compound therewith. I may employ any type of
rolling machine, but I preferably employ the tea leaf rolling machine described
in the Specification of previous Letters Patent granted to me No. 22149 dated
6th October 1896. The addition of the compound can be very evenly and per-
fectly effected in this machine because the receptacle for containing the leaf while
being rolled is constructed to work with the top uncovered, which allows of the
compound being very equally sifted over the leaf, and during the rolling operation
the leaf receives a continuous "boiling up" movement, which causes a very
rapid and perfect circulation of the leaves throughout the mass, and incorporation
of the compound therewith, together with excellent aeration of the leaf, which
facilitates its absorption of oxygen.
The compound may be added to the leaf at any stage during or prior to the
operation of rolling, but I preferably add it while the leaf is being rolled, as a
considerable amount of the juices are usually expressed during this process, and
_by_adding the compound after the surfaces of the leaf have become moist, the
further rolling-of-the-leaf very quickly and thoroughly amalgamates it therewith.
The most suitable duration of time-which-should be allowed to elapse between
the rolling and subsequent drying of the leaf, can easily be ascertained by a
few experimental trials, and cannot here be definitely stated, as different growths
of leaf, and different temperatures and other atmospheric conditions of the factory
in which the manufacture is being conducted, influence this point, but in all
cases the time required is considerably less than would be necessary if the leaf
were manufactured without the compound. If the leaf has been artificially
withered in accordance with the method, and by the apparatus described in the
Specification of previous Letters Patent granted to me No. 1125 of 15th January
1897, the operative effects of the compound are very evident and pronounced, as
the leaf after being thus withered, and when treated with the compound during
the rolling operation, has its oxidation sufficiently advanced by the time its
rolling process is completed, for it to be taken directly on completion of the
rolling process, to the drying, without any interval of time being allowed to
elapse between the one process and the other, as by this method of manufacture
the leaf is warm while being rolled, and its tendency to absorb oxygen is thereby
enhanced. Consequently with this system of manufacture, in combination with
the employment of the compound, the time required for the oxidation of the
leaf is reduced to a minimuni, and the black tea produced thereby is equivalently
superior in quality.
The new and improved technical effects produced on the leaf and its juices
after the compound has been added and thoroughly mixed therewith, are a more
rapid and advantageous absorption of oxygen thereby, greater solubility of the
mucilagenous and albuminoid constituents, whereby they amalgamate more
thoroughly and completely with the other constituents of the leaf and juices
during the rolling process, the combined results of which, provided the subsequent
drying of the leaf be properly done, and at the most suitable time (according to
circumstances of manufacture) after the leaf comes out of the rolling machine,
are that the black teas obtained are of improved quality and higher market
value.
In order to facilitate and ensure the proper admixture of the sugar and alkali

page_text: in the compound, a trace of any suitable coloring matter which is neutral and
inactive in regard to the juices of the tea leaf may be added to the first constituent.
put into the grinding and mixing machine and when this constituent has become.
colored throughout by mixture with the colouring matter the next constituent
may be added and the grinding and mixing continued. The mixing of the.
substances in the machine can then be visibly followed until their complete and
thorough amalgamation is evidenced by the material having attained a uniform
color throughout.
Improvements in the Manufacture of Black Tea from the Green Tea
Leaf, and a New Compound for Use in such Manufacture.
I, SAMUEL CLELAND DAVIDSON, of Sirocco Engineering Works, Belfast, Ireland,
Merchant, 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 treatment of tea leaf in the course of its manu-
facture into what is commercially known as black tea, and it consists of an
improvement in the treatment of the leaf and also of a new compound for use in
such treatment.
In the manufacture of tea leaf into black tea, according to the method hitherto
ordinarily followed the leaf is first withered, then rolled, after which, and while
still in a moist state, it undergoes a process of oxidation which is generally
known as
fermentation," during which it absorbs oxygen, whereby it loses its
green colour and becomes a brownish tint.
"
The successful accomplishment of the changes which are effected in the leaf,
by its proper absorption of oxygen, determines to an important extent the subse-
quent quality of the tea, after its manufacture has been completed by the final
drying of the leaf.
If the condition of the leaf and the nature of its juices, when it is being manu-
factured, are such that a long continuance of the fermentation process is required,
in order to effect the requisite absorption of oxygen and other necessary changes
for the production of black tea, the quality of the liquor obtained by infusing
the finished tea (hereinafter referred to as the infusion) is depreciated, owing
to the fact that a long duration of the fermentation process also involves further
changes taking place in the leaf and juices of a detrimental nature, which render
their albuminoid constituents less soluble in the infusion and which at the same
time materially reduce the pungency and strength of the infusion.
Accordingly the object of the present invention is to so treat the leaf after it has
been withered, and while it is being subsequently rolled, that its tendency to
absorb oxygen is enhanced, whereby the duration of the process is greatly.
curtailed, the said absorption more advantageously effected, the originally con-
tained pungency and strength of the leaf and juices more fully preserved, and
the solubility of the albuminoid constituents increased, so that the resulting
black tea produces a richer coloured and stronger infusion, and is of improved
market value.

page_text: This invention consists in adding to the leaf, after it has undergone the above
referred to withering process, and during the subsequent rolling operation,
approximately one-half to one per cent. of its weight of a compound, consisting
of ordinary sugar ground into a fine powder, with an alkaline substance, such as
the carbonate or bi-carbonate of soda, potash or magnesia, or an admixture thereof
(hereinafter referred to as the alkali) in the proportion of preferably three parts
of sugar to one part of the alkali (and which combination of sugar and alkali is
hereinafter referred to as the compound); but I do not limit myself..to the
particular proportions of sugar and alkali herein stated, or to any exact per-
centage of the compound which may be applied to the leaf; as the quantity may
be varied to suit special growths of the tea leaf; but the proportions and percentage
above stated answer well in ordinary cases...
The incorporation of the compound into the leaf is conveniently effected by
sifting it gradually over the same while it is undergoing the rolling operation,
and preferably after the surfaces of the leaf have become slightly moistened by
the exuding juices, after which the further squeezing and turning over and over
to which the leaf is subjected before its rolling is completed, very thoroughly
mixes and incorporates the compound therewith. I may employ any type of
rolling machine, but I preferably employ the tea leaf rolling machine described
in the Specification of a previous Letters Patent granted to me, and dated 6th
October 1896 No. 22,149. The addition of the compound can be very evenly and per-
fectly effected in this machine because the receptacle for containing the leaf while
being rolled is constructed to work with the top uncovered, which allows of the
compound being very equally sifted over the leaf, and during the rolling operation
the leaf receives a continuous boiling up" movement, which causes a very
rapid and perfect circulation of the leaves throughout the mass, and incorporation-
of the compound therewith, together with excellent aeration of the leaf, which
facilitates its absorption of oxygen.
The compound may be added to the leaf at any stage during or prior to the
operation of rolling, but I preferably add it while the leaf is being rolled; -as-a
considerable amount of the juices are usually expressed during this process, and
by adding the compound after the surfaces of the leaf have become moist, the
further rolling of the leaf very quickly and thoroughly amalgamates it therewith.
The most suitable duration of time which should be allowed to elapse between
the rolling and subsequent drying of the leaf, can easily be ascertained by a
few experimental trials, and cannot here be definitely stated, as different growths
of leaf, and different temperatures and other atmospheric conditions of the factory
in which the manufacture is being conducted, influence this point, but in all
cases the time required is considerably less than would be necessary if the leaf
were manufactured without the compound. If the leaf has been artificially
withered in accordance with the method, and by the apparatus described in the
Specification of previous Letters Patent granted to me, and dated 15th January 1897
No. 1,125, the operative effects of the compound are very evident and pronounced, as
the leaf after being thus withered, and when treated with the compound during
the rolling operation, has its oxidation sufficiently advanced by the time its
rolling process is completed, for it to be taken directly on completion of the
rolling process, to the drying, without any interval of time being allowed to
elapse between the one process and the other, as by this method of manufacture
the leaf is warm while being rolled, and its tendency to absorb oxygen is thereby
enhanced. Consequently with this system of manufacture, in combination with
the employment of the compound, the time required for the oxidation of the
leaf is reduced to a minimum, and the black tea produced thereby is equivalently
superior in quality.
The new and improved technical effects produced on the leaf and its juices
after the compound has been added and thoroughly mixed therewith, are a more
rapid and advantageous absorption of oxygen thereby, greater solubility of the
mucilagenous and albuminoid constituents, whereby they amalgamate more

page_text: thoroughly and completely with the other constituents of the leaf and juices
during the rolling process, the combined results of which, provided the subsequent
drying of the leaf be properly done, and at the most suitable time (according to
circumstances of manufacture) after the leaf comes out of the rolling machine,
are that the black teas obtained are of improved quality and higher market
value.
I am aware that the addition of alkaline carbonates or bicarbonates to tea leaf
in the course of its manufacture into black tea, in order to produce a richer
coloured infusion, is not new, having myself been already granted exclusive
privileges in India and Ceylon, dated respectively 14th October 1892 No. 158.
of 1892, and 20th July 1892 No. 390, for the employment of alkalies or alkaline
carbonates in the manufacture of tea leaf into black tea, but the novel combina-
tion of said alkaline carbonates or bi-carbonates with a suitable proportion of
sugar, which combination is an essential feature of the present invention, produces
new technical effects during the manufacture of the leaf, whereby the quality of
the resulting black tea is improved.
In order to facilitate and ensure the proper admixture of the sugar and alkali
in the compound, a trace of any suitable coloring matter which is neutral and
inactive in regard to the juices of the tea leaf may be added to the first constituent
put into the grinding and mixing machine and when this constituent has become
coloured throughout by mixture with the colouring matter the next constituent
may be added and the grinding and mixing continued. The mixing of the
substances in the machine can then be visibly followed until their complete and
thorough amalgamation is evidenced by the material having attained a uniform
color throughout.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. The addition to tea leaf in and during the process of manufacture of same
into black tea, of a compound consisting of sugar in combination with an alkali
or alkaline carbonate or bi-carbonate of soda, potash, or magnesia, or any suitable
admixture thereof, all substantially as and for the purpose set forth.
2. A new compound for use in the manuafcture of black tea from the tea leaf,
the said compound consiting of sugar and an alkali with or without a neutral
inactive colouring matter, substantially as and for the purpose set forth.
Dated this 23rd day of November 1899.
J. C. MEWBURN & ELLIS,
55 and 56, Chancery Lane, London, Chartered Patent Agents.