Theory of Colours — trans. Charles Lock Eastlake (1840)

The mineral chameleon, a name which has been given to an oxyde of manganese, may be considered, in its perfectly dry state, as a green powder. If we strew it in water, the green colour displays itself very beautifully in the first moment of solution, but it changes presently to the bright red opposite to green, without any apparent intermediate state.

543.

The same occurs with the sympathetic ink, which may be considered a reddish liquid, but which, when dried by warmth, appears as a green colour on paper.

544.

In fact, this phenomenon appears to be owing to the conflict between a dry and moist state, as has been already observed, if we are not mistaken, by the chemists. We may look to the improvements of time to point out what may further be deduced from these phenomena, and to show what other facts they may be connected with.

XLIII.

FIXATION.

545.

Mutable as we have hitherto found colour to be, even as a substance, yet under certain circumstances it may at last be fixed.

546.

There are bodies capable of being entirely converted into colouring matter: here it may be said that the colour fixes itself in its own substance, stops at a certain point, and is there defined. Such colouring substances are found throughout nature; the vegetable world affords a great quantity of examples, among which some are particularly distinguished, and may be considered as the representatives of the rest; such as, on the active side, madder, on the passive side, indigo.

547.

In order to make these materials available in use, it is necessary that the colouring quality in them should be intimately condensed, and the tinging substance refined, practically speaking, to an infinite divisibility. This is accomplished in various ways, and particularly by the well-known means of fermentation and decomposition.

548.

These colouring substances now attach themselves again to other bodies. Thus, in the mineral kingdom they adhere to earths and metallic oxydes; they unite in melting with glasses; and in this case, as the light is transmitted through them, they appear in the greatest beauty, while an eternal duration may be ascribed to them.

549.

They fasten on vegetable and animal bodies with more or less power, and remain more or less permanently; partly owing to their nature,--as yellow, for instance, is more evanescent than blue,--or owing to the nature of the substance on which they appear. They last less in vegetable than in animal substances, and even within this latter kingdom there are again varieties. Hemp or cotton threads, silk or wool, exhibit very different relations to colouring substances.

550.

Here comes into the account the important operation of employing mordants, which may be considered as the intermediate agents between the colour and the recipient substance; various works on dyeing speak of this circumstantially. Suffice it to have alluded to processes by means of which the colour retains a permanency only to be destroyed with the substance, and which may even increase in brightness and beauty by use.

XLIV.

INTERMIXTURE, REAL.

551.

Every intermixture pre-supposes a specific state of colour; and thus when we speak of intermixture, we here understand it in an atomic sense. We must first have before us certain bodies arrested at any given point of the colorific circle, before we can produce gradations by their union.

552.

Yellow, blue, and red, may be assumed as pure elementary colours, already existing; from these, violet, orange, and green, are the simplest combined results.

553.

Some persons have taken much pains to define these intermixtures more accurately, by relations of number, measure, and weight, but nothing very profitable has been thus accomplished.

554.

Painting consists, strictly speaking, in the intermixture of such specific colouring bodies and their infinite possible combinations--combinations which can only be appreciated by the nicest, most practised eye, and only accomplished under its influence.

555.

The intimate combination of these ingredients is effected, in the first instance, through the most perfect comminution of the material by means of grinding, washing, &c., as well as by vehicles or liquid mediums which hold together the pulverized substance, and combine organically, as it were, the unorganic; such are the oils, resins, &c.--Note V.

556.

If all the colours are mixed together they retain their general character as σκιερόν, and as they are no longer seen next each other, no completeness, no harmony, is experienced; the result is grey, which, like apparent colour, always appears somewhat darker than white, and somewhat lighter than black.

557.