The colours denominated by dyers simple, 
because they are the foundation of all their 
other processes, are four ; namely, first, blue ; 
Second, yellow; third, red ; fourth, black. 
To these they usually add a fifth, under the 
name of root or brown colour. 
Of dyeing blue :. — The only colouring mat- 
ters employed in dyeing blue, are woad and 
indigo. 
Woad is a plant cultivated in this kingdom, 
and even growing wild in some parts of Eng- 
land. 
Indigo is a blue powder, extracted from a 
spucies of plant which is cultivated for that 
purpose in the East and West Indies. These 
plants contain a peculiar green pollen, which 
in that state is soluble in water. This pollen 
has a strong affinity for oxygen, which it at- 
tracts greedily from the atmosphere; in con- 
sequence of which it assumes a blue colour, 
and becomes insoluble in water. 
Indigo has a very strong affinity for wool, 
silk, cotton, and linen. Every kind of cloth, 
therefore, may lie dyed with it, without the 
assistance of any mordant whatever. The 
colour thus induced is very permanent ; 
because the indigo is already saturated with 
oxygen, and because it is not liable to be de- 
composed by those substances, to the action 
of which the cloth is exposed, hut it can 
only be applied to cloth in a state of solution ; 
and the only solvent known being sulphuric 
acid, it would seem at first sight, that the 
sulphuric acid solution is the only state in j 
which indigo can be employed as a dye. 
The sulphate of indigo is indeed often used 
to dye wool and silk blue ; but it can scarcely | 
be applied to cotton and linen, because the 
affinity of these substances for indigo is not j 
great enough to enable them readily to de- 
compose the sulphate. The colour given 
by sulphate of indigo is exceedingly beaut i- , 
fill ; it is known by the name of Saxon blue. | 
One part of indigo is to be dissolved in four ! 
parts of concentrated sulphuric acid; to the : 
solution one part of dry carbonate of potass 
is to be added, and then it is to be diluted , 
with eight times its weight of water. The 
cloth must be boiled for an hour in a solu- 
tion, containing five parts of alum, and three 
of tartar, for every 32 parts of cloth. It is 
then to be thrown into a water-bath, con- 
taining a greater or smaller proportion of the 
diluted sulphate of indigo, according to the 
shade which the cloth is intended to receive. 
In this bath it must be boiled till it has ac- 
quired the wished-for colour. 
The alum and tartar are not intended to 
act as mordants, but to facilitate the decom- 
position of the sulphate of indigo. The 
alkali added to the sulphate, answers the 
same purpose. These substances also, by 
saturating part of the sulphuric acid, serve in 
some measure to prevent the texture of the 
cloth from being injured by the action of the 
acid, which is very apt to happen in this pro- 
cess. 
But sulphate of indigo is by no means the 
only solution of that pigment employed in 
dyeing. By far the most common method 
is, to deprive indigo of the oxygen, to which 
it owes its blue colour, and thus to reduce it 
to the state of green pollen ; and then to dis- 
solve it in water by means of alkalis, or alka- 
line earths, which in that state act upon it 
very readily. 
'Two different methods are employed for 
this purpose. The first of these methods is, to ' 
DYEING. 
mix with indigo a solution of some substance 
which has a stronger affinity for oxygen than 
the green basis of indigo ; green oxide, for 
instance, and different metallic sulphurets. 
If therefore indigo, lime, ami green sulphate 
of iron, are mixed together in water, the in- 
digo gradually loses its blue colour, becomes 
green, and is dissolved ; while the green 
oxide of iron is converted into the red oxide. 
The manner in which these changes take 
place is obvious; part of the lime decom- 
poses the sulphate of iron.; the green oxide, 
the instant that it is set at liberty, attracts 
oxygen from the indigo, decomposes it, and 
reduces it to the state of green pollen. This 
green pollen is immediately dissolved by the 
action of the rest of the lime. 
The second method is, to mix the indigo 
in water with certain vegetable substances, 
which readily undergo fermentation. Dur- 
ing this fermentation, the indigo is deprived 
of its oxygen, and dissolved by means of 
quick-lime or alkali, which is added lo the 
solution. The first of these methods is usu- 
ally followed in dyeing cotton and linen; the 
second, in dyeing wool and silk. 
In the dyeing of wool, woad and bran are 
commonly employed as vegetable ferments, 
and lime as the solvent of the green base of 
the indigo. Woad itseif contains a colouring 
matter precisely similar to indigo; and bv 
following the common process, indigo mav 
be extracted from it. in the usual state of j 
woad, when purchased by the dyer, the in- \ 
digo which it contains is probably not far j 
from the state of the green pollen. Its quan- 
tity in woad is but small, and it is mixed with 
a great proportion of other vegetable matter. 
When the cloth is first taken out of the 
vat, it is of a green colour ; but it soon be- 
comes blue, by attracting oxygen from the 
air. It ought to be carefully washed, to 
carry off the uncombined particles. This’ 
solution of indigo is liable to two inconveni- 
ences : first, it is apt sometimes to run too 
fast into tire putrid fermentation ; this may 
be known by the putrid vapours which it ex- 
hales, and by the disappearing of the green 
colour. In this state it would soon destroy 
the indigo altogether. The inconvenience 
is remedied by adding more lime, which has 
the property of moderating the putrescent 
tendency. Secondly, sometimes the fermen- 
tation goes on too languidly. This defect 
is remedied by adding more bran or woad, 
in order to diminish the proportion of quick- 
lime. 
Silk is dyed light-blue by a ferment of 
six parts of bran six of indigo, six of potass, 
and one of madder. To dye it of a dark 
blue, it must previously receive what is called 
a ground-colour; a red dye-stuff, called 
archil, is used for this purpose. 
Cotton and linen are dyed blue by a so- 
lution of one part of indigo, one part of green 
sulphate of iron, and two parts of quick-lime. 
Of dyeing yelloiv . — The principal colour- 
ing matters for dyeing yellow are weld, fustic, 
and quercitron bark. 
W eld is a plant which grows commonly in 
tins country, reseda .luteoia. 
Fustic is the wood of a large tree which 
grows in. the West Indies, morus tinctoria. 
Quercitron is a tree growing in North 
America, the bark of which contains colouring 
matter. 
Yellow colouring matters have too weak 
an affinity for cictn, to produce pemyment ' 
5/3 
I colours without the use of mordants. Cloth, 
therefore, before it is dyed yellow, is always 
prepared by combining some mordant or 
other with it. The mordant most com- 
monly employed for this purpose, is alumina. 
Oxide of tin is sometimes used when very 
fine yellows are wanting. Tan is otten em- 
ployed as a subsidiary to alumina, and in 
order to fix it more copiously on cotton and 
linen. Tartar is also used as an auxiliary, 
to brighten the colour; and muriate of soda, 
sulphate of lime, and even sulphate of iron, 
in order to render the shade deeper. 
The yellow dyed by means of fustic is 
more permanent, but not so beautiful as that 
given by weld, or quercitron. As it is per- 
manent, and not much injured by acids, it is, 
ofteu used in dyeing compound colours, 
where a yellow is required. The mordant is 
alumina. When the mordant is oxide of iron, 
fustic dyes a good permanent drab colour. 
Weld and quercitron bark yield nearly 
the same kind of colour; but as the bark 
yields colouring matter in much greater 
abundance, it is much more convenient, and 
upon the whole, cheaper than weld. It is 
probable, therefore, that it will gradually 
supersede the use ,of that plant. The me- 
thod of using each of these dye-stuffs ttis 
nearly the. same. 
Wool may be dyed yellow by the follow- 
ing process:” Let it be boiled for an hour or 
more with about -Ith of its weight of alum,, 
dissolved in a sufficient quantity of water. 
I I is then to be plunged, without being rinsed, ' 
into a bath of warm water, containing in it 
as much quercitron bark, as equals the weight 
of the alum employed as a mordant. Tha 
cloth is to be turned through the boiling 
liquid, till it has acquired the intended 
colour. Then a quantity of clean powdered 
chalk, equal lo the hundredth part of the 
'weight of tire cloth, is to be stirred in, and 
the operation of dyeing continued for eight 
or ten minutes longer. By this method a 
pretty deep and lively yellow may be given,, 
fully as permanent as weld yellow. 
For very bright orange or golden yellow, 
it is necessary to have recourse to the oxide 
of tin as a mordant. 
For producing bright golden yellows, some 
alum must be added along w ith the tin. 
In order to give the yellow that delicate 
green shade so much admired for certain 
purposes, tartar must be added in different 
proportions, according to the shade. 
By adding a small proportion of cochineal, 
the colour may be raised to a fine orange, 
or even an aurora. 
Silk may be dyed different shades of yel- 
low, either by weld or quercitron bark, but 
the last is the cheapest of the two. The pro- 
portion should be from one to two parts of 
bark to twelve parts of silk, according to the 
shade. The bark, tied up in a bag, should 
be put into the dyeihg vessel, while the wates* 
which it contains is cold ; and when it ha-? 
acquired the heat of about 100°, the silk, 
having been previously alumed, should be 
dipped in, and continued till it assumes the 
wished-for colour. When the shade is re- 
quired to be deep, a little chalk or pearl-ash 
should be added towards the end of the ope- 
ration. 
The best method of dyeing cotton and 
linen yellow', is as follows : 
'Fhe mordant should be acetite of alumina, 
prepared joy dissolving one part of acetite of 
