Process for Rendering Wool Dyeings Fast to "Potting" or 66 Spungeing."
Year: 1895

page_text: Date of Application, 9th Dec., 1895-Accepted, 11th Jan., 1896
COMPLETE SPECIFICATION.
Process for Rendering Wool Dyeings Fast to "Potting" or
66
Spungeing."
I, SYDNEY PITT, of Sutton in the County of Surrey, do hereby declare the
nature of this invention (which has been communicated to me from abroad by
Leopold Cassella and Co. of Frankfort-on-Main, in the Empire of Germany)
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
The shades of wool dyed with certain azo dyestuffs undergo a considerable
alteration, when subjected to a high temperature. Such a treatment is unavoidable
in the so called "potting" process applied to dyed woollen piece goods, and the
discovery of a method which paralyses the sensitiveness of such dyeings to the
influence of high temperatures, and thus renders them fast to "potting" is of great
practical value.
It has been observed that the change of the shades by the influence of heat is
due to a splitting of the azo groups. This can for instance be demonstrated with
polyazo dyestuffs the azo groups of which are successively destroyed thus the
shades of black diazo dyestuffs derived from amidoazonaphtalinesulpho acids are
first turned into red and at this stage the amidoazo compound can be recognised on
the fibre. On the basis of these observations tests were made to paralyse the effect
of the animal fibre by adding oxidizers or easily reducible bodies and the desired
result was really obtained.
First it was found that only such oxidizers are applicable as are not too easily
changed by the animal fibre before the application of the "potting" process.
Bichromates and permanganates consequently do not give the desired effect whilst,
for instance, chlorates and salts of copper oxides are excellently suitable.
The process itself is very simple as it is only necessary to impregnate the dyed
cloth with a solution of the oxydizing salt which is either done in the dye-bath or
after dyeing.
The quantity of the oxydizing salt required depends on the depth of the dyeing
and also on the quality of the wool.
But generally:
3 to 4% sulphate of copper of the weight of the wool, or
5 to 8% chlorate of soda
"
"
"
11 T
C
When applying salts of copper the goods after being dyed or impregnated may
be washed which is however to be avoided when chlorate of sodium bas been
used.
As dyestuffs which especially are by this process fixed fast for "potting” I
enumerate the basic dyestuffs of the naphtylamine black group, naphtylamine
black D, naphtyl blue black N, anthracite black, jet black, sulphone black, etc. etc.
although the application of this method is not at all confined to these.
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 :-
The process of rendering wool dyeings fast to the influence of high temperatures

page_text: such as are applied in potting or spungeing by impregnating them with oxydizing
bodies or easily reducible substances such as chlorates or salts of copper oxides
substantially as described.
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