DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20658#0315
COLOURING SUBSTANCES.
301
fourth may be added in the same way. In this manner any other colour may be applied ; and
it is the only one by which orpiment can be employed, so as to preserve all its beauty, although
retaining some of its defects. Another way of executing this kind of work is to apply the
colours and the varnish without previously using the size and the white ground. This method
is very expeditious, but it has the defect of not being susceptible of the high polish and brilliancy
of the former method.
CHAP. VII.
of the nature; composition, and qualities of different colouring
substances.
Although from early habits we are accustomed to suppose that colours really exist in
bodies, yet it is certain that the term colour denotes no property in these substances, but simply
a modification of our minds. Colour belongs inherently to light by which, according to the
various sizes of its parts, or from other cause, it excites different vibrations in the optic nerves,
which being propagated to the sensorium affect the mind with different sensations. Colours in
painting are distinguished as they mean the drugs and other substances producing them, and as
the tints and hues produced by those materials variously combined and applied.
Colour-making, or the art of preparing different sorts of colours, properly belongs to chemistry t
and is one of its most curious but least understood parts ; the principles on which it depends
being quite different from those on which the theory of other parts of chemistry is founded j and
the practice of it being generally kept a profound secret by those employed in the art. .
The rays of light present to our eyes only seven principal or primitive colours, which are red,
orange, yellow, green, blue, indigo, and violet; all the others from white down to black being
only mixtures of these principal colours differently combined. The white and black, it is true,
cannot with propriety be ranked among colours, the white being only a general result from
compounding all the other colours together in certain proportions, and black being a privation
or absence of all colour.
The colours used in painting are composed of mineral, vegetable or animal substances, either
taken separately or combined together in various ways,
One of the chief colouring substances is iron, the effects of which are to be traced in many
■other bodies. Its different solutions produce yellow, orange, red, violet, blue and black.—Copper
gives blue, green, and black.—Gold, when in the state of a calx or oxyde, furnishes purple or
violet, brown and black.—Lead, dissolved and calcined produces white, grey, minium or red lead,
litharge either black or yellow, and black : a solution of tin gives to scarlet great part of its
brilliancy: cobalt produces the blue colour of enamel; and a combination of mercury and
sulphur makes a red colour called cinnabar or vermilion.
In painting the expression local colours is used for those which, by their situation, and the
help of some other colours, represent any particular object, as the flesh, linen, stuffs, &c. and
they are called local because the place they occupy requires such particular colours to give it its
4 h due
301
fourth may be added in the same way. In this manner any other colour may be applied ; and
it is the only one by which orpiment can be employed, so as to preserve all its beauty, although
retaining some of its defects. Another way of executing this kind of work is to apply the
colours and the varnish without previously using the size and the white ground. This method
is very expeditious, but it has the defect of not being susceptible of the high polish and brilliancy
of the former method.
CHAP. VII.
of the nature; composition, and qualities of different colouring
substances.
Although from early habits we are accustomed to suppose that colours really exist in
bodies, yet it is certain that the term colour denotes no property in these substances, but simply
a modification of our minds. Colour belongs inherently to light by which, according to the
various sizes of its parts, or from other cause, it excites different vibrations in the optic nerves,
which being propagated to the sensorium affect the mind with different sensations. Colours in
painting are distinguished as they mean the drugs and other substances producing them, and as
the tints and hues produced by those materials variously combined and applied.
Colour-making, or the art of preparing different sorts of colours, properly belongs to chemistry t
and is one of its most curious but least understood parts ; the principles on which it depends
being quite different from those on which the theory of other parts of chemistry is founded j and
the practice of it being generally kept a profound secret by those employed in the art. .
The rays of light present to our eyes only seven principal or primitive colours, which are red,
orange, yellow, green, blue, indigo, and violet; all the others from white down to black being
only mixtures of these principal colours differently combined. The white and black, it is true,
cannot with propriety be ranked among colours, the white being only a general result from
compounding all the other colours together in certain proportions, and black being a privation
or absence of all colour.
The colours used in painting are composed of mineral, vegetable or animal substances, either
taken separately or combined together in various ways,
One of the chief colouring substances is iron, the effects of which are to be traced in many
■other bodies. Its different solutions produce yellow, orange, red, violet, blue and black.—Copper
gives blue, green, and black.—Gold, when in the state of a calx or oxyde, furnishes purple or
violet, brown and black.—Lead, dissolved and calcined produces white, grey, minium or red lead,
litharge either black or yellow, and black : a solution of tin gives to scarlet great part of its
brilliancy: cobalt produces the blue colour of enamel; and a combination of mercury and
sulphur makes a red colour called cinnabar or vermilion.
In painting the expression local colours is used for those which, by their situation, and the
help of some other colours, represent any particular object, as the flesh, linen, stuffs, &c. and
they are called local because the place they occupy requires such particular colours to give it its
4 h due