INK. 
iion. A little carmine also improves the 
colour. (Encycl. Arts & Metiers, vol. iii. 
p. 518.) 
Inks, coloured. Few of these are used 
except red ink. The preparation of these 
is very simple, consisting either of decoc- 
tions of the different colouring or dying 
materials in water, and thickened with 
gum-arabic, or of coloured metallic oxides 
or insoluble powders, merely diffused in 
gum-water. The proportion of gum-arabic 
to be used may be the same as for black 
writing ink. All that applies to the fixed 
or fugitive nature of the several articles 
used in dying, may be applied in general 
to the use of the same substances as inks. 
Ink, red, is usually made by boiling about 
two ounces of Brazil wood in a pint of wa- 
ter, for a quarter of an hour, and adding 
to the decoction the requisite quantity of 
gum, and about half as much alum. The 
alum both heightens the colour and makes 
it less fugitive. Probably a little madder 
would make it more durable. 
Ink, , blue, may be made by diffusing 
Prussian blue or indigo through strong gum- 
water. 
\nn, yellow, may be made by a solution of 
gamboge in gum-water. 
Most of the common water-colour cakes 
diffused in water, will make sufficiently 
good coloured inks for most purposes. 
Inks of other colours may be made from 
a strong decoction of the ingredients used 
in dying, mixed with a little alum and gum 
arabic. For example, a strong decoction 
of Brazil wood, with as much alum as it can 
dissolve, and a little gum, forms a good red 
ink. These processes consist in forming a 
lake, and retarding its precipitation by the 
gum. See Lake. 
On many occasions it is of importance to 
employ an ink indestructible by any pro- 
cess, that will not equally destroy the ma- 
terial on which it is applied. Mr. Close 
has recommended for this purpose 25 grains 
of copal in powder dissolved in 200 grains 
of oil of lavender, by the assistance of gentle 
heat, and then mixed with 2| grains of lamp 
black and half a grain of indigo : or 120 grains 
of oil of lavender, 17 grains of copal, and 
60 grains of vermilion. A little oil of laven- 
der, or of turpentine, may be added, if the 
ink be found too thick. Mr. Sheldrake 
suggests, that a mixture of genuine asphal- 
tum dissolved in oil of turpentine, amber 
varnish, and lamp black, would be still su- 
perior. 
When writing with common ink has been 
effaced by means of oxygenized muriatic 
acid, the vapour of sulphuret of ammonia, 
or immersion in water impregnated with 
this sulphuret, will render it again legible. 
Or if the paper that contained the writing 
be put into a weak solution of prussiate of 
potash, and when it is thoroughly wet a 
sulphuric acid be added to the liquor, so as 
to render it slightly acidulous, the same 
purpose will be answered. 
Mr. Haussman has given some composi- 
tions for marking pieces of cotton or linen, 
previous to their being bleached, which are 
capable of resisting every operation in the 
processes both of bleaching and dying, and 
consequently might be employed in mark- 
ing linen for domestic purposes. One of 
these consists of asphaltum dissolved in 
about four parts of oil of turpentine, and 
with this is to be mixed lamp black, or black 
lead in fine powder, so as to make an ink 
of a proper consistence for printing with 
types. Another, the blackish sulphate left 
after expelling oxygen gas from oxide of 
manganese with a moderate heat being dis- 
solved and filtered, the dark grey pasty 
oxide left on the filter is to be mixed with 
a very little solution of gum tragacanth, and 
the cloth marked with this is to be dipped 
in a solution of potash or soda, mild or 
caustic, in about ten parts of water. 
Among the amusing experiments of the 
art of chemistry, the exhibition of sympa- 
thetic inks holds a distinguished place. 
With these the writing is invisible, until 
some reagent gives it opacity. We shall 
here mention a few out of the great num- 
ber, that a slight acquaintance with che- 
mistry may suggest to the student. 1, If a 
weak infusion of galls be used, the writing 
will be invisible till the paper be moistened 
with a weak solution of sulphate of iron. It 
then becomes black, because these ingre- 
dients form ink. 2. If paper be soaked in a 
weak infusion of galls, and dried, a pen dipped 
in the solution of sulphate of iron will write 
. black on that paper, but colourless on any 
other paper. 3. The diluted solutions of 
gold, silver, or mercury, remain colourless 
upon the paper, till exposed to the sun’s 
light, which gives a dark colour to the ox- 
ides, and renders them visible. 4. Most of 
the acids or saline solutions being diluted, 
and used to write with, become visible by 
heating before the fire, which concentrates 
them, and assists their action on the paper. 
5. Diluted prussiate of potash affords blue 
letters when wetted with the solution of 
sulphate of iron. 6. The solution of cobalt 
