Hence you perceive that prussian blue cannot be a permanent colour, unless prepared with red oxyd of iron, since by exposure to the atmosphere it gradually darkens, and in a short time is no longer in harmony with the other colours of the painting.
CAROLINE.
But it can never become darker, by exposure to the atmosphere, than the true prussian blue, in which the oxyd is perfectly saturated?
MRS. B.
Certainly not. But in painting, the artist not reckoning upon partial alterations in his colours, gives his blue tints that particular shade which harmonises with the rest of the picture. If, afterwards, those tints become darker, the harmony of the colouring must necessarily be destroyed.
CAROLINE.
Pray, of what nature is the paint called carmine?
MRS. B.
It is an animal colour prepared from cochineal, an insect, the infusion of which produces a very beautiful red.
CAROLINE.