IMPROVEMENTS IN DYEING
Year: 1853

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition,
on the 14th March 1853.
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County
of Middlesex, and of Glasgow, North Britain, Gentleman, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN DYEING
to be as follows:-
This Invention relates as well to the securing superior solidity of
colour, in dyeing processes, for all fibrous substances, whilst brilliancy
and beauty are preserved, as to the obtainment of economy in the
manufacturing cost. Hitherto, in dyeing silk, gall apples have been
used, either alone, or combined with an oxide of iron, to increase the
density of the silk; this addition making up for the weight lost in the
dyeing process. Silk so treated is termed "charged," and is recognized
as being very superior, but the substances involved in the treatment are
costly; and in adopting (according to this Invention) a new means of
charging silks dyed in black and other colours, the fibrous matters

page_text: are softened, and superior brilliancy is arrived at, at a cheap rate.
The essential feature of the Invention is based on the use of pure
nitrate of iron, and partly on nectate and sub-acetate of lead.
In dyeing black, violet, and other colours, the bath is made up of
sub-acetate of load and litharge water, and pyroligneous acid. The
puro nitrate of iron is prepared with nitric acid and new bars of iron
of a certain thickness, in order that the operation may progress slowly.
The silk, if to be dyed a darker or lighter shade of black, is first boiled
and then washed, and afterwards placed in a bath of nitrate of iron.
The treated fabric is then exposed to the air, and is then washed in
flowing water. The material is then again irumersed in a bath
of nitrate of iron, and the processes already described are repeated to
the extent found necessary. A bath is then prepared, for example, of
extract of logwood and wood quercitron, or "bois jaune," and to this
mixture a solution of sulphate of copper is added. The silk is then
immersed in this bath, when they receive a magnificent black colour;
and this is followed by a washing in running water, and afterwards by
a plunging into a tepid bath of water, in which a small quantity of oil
decomposed by carbonate of soda has been poured. The process is
finally completed plunging the silk into a boiler containing the sub-
acetate of lead, this treatment producing the augmentation of weight.
But the black so produced is of a light shade, and, to darken it, it is
dried in a low temperature, and exposed to a current of sulphuric acid.
This gives a pure and brilliant black, whilst the colour is solid. It is to
be understood that all those metals which by their combinations with
acids or gases produce agents or compositions, the chemical or physical
qualities of which are the same as those obtained by the process herein
indicated, must, necessarily, form part of the essential principle of
improvements. For colours, a bath termed the "charged" bath, com-
posed either of sub-acetate or acetate of lead, according as the reaction
is more or less favorable, is used, in order that it may compete
with the bath charged with sugar of lead, or other ingredient hitherto
used.
The acetate of lead is superior to all the alkaline solutions, as far as
solidity of colour is concerned, as proved by the violet obtained from the

page_text: alga tinctoria" or white moss. Under its influence the woad acquires
great solidity, and becomes golden. Thus the principle of the Invention
rests on the use of nitrate of iron and the acetate and sub-acetate
of lead, or any other agent or composite material with a metallic basc,
possessing the same properties, as fulfilling the special conditions herein
referred to.