Red, is one of the simple or primary colours, into which the rays of light divide themselves, on being refracted through a prism.

The principal reds employed in painting are, carmine, rose-pink, red-lead, and vermilion; of the preparation of which, the reader will find a concise account, vol. ii. p. 36.

In dyeing, the chief articles that afford a red shade, with its different varieties, are kermes, cochineal, and madder. - See Dyeing, vol. ii. pp. 203-5.

In the 2d volume of the New Memoirs of the Royal Academy, of Sciences, etc. of Berlin, we meet with a communication by M. MargRaaff, containing an account of an excellent red paint. Its component parts are Dutch madder, and alum; which, being mixed with a small portion of the oil of poppies, afford a colour of exquisite beauty and lustre, far superior to the red obtained from cochineal, or any other vegetable Substitute; while it is considerably cheaper; though, he observes, the quantity of distilled water used in the process, increases the expence of the preparation.

Red-INk, is a coloured liquor employed for the ruling of account-books, and other mercantile purposes. It is prepared by infusing 4 ounces of the raspings of Brazilwood, and 2 drams of pulverized alum, in equal quantities, namely, a pint of rain-water and vinegar, for two or three days; at the expiration of which time, the infusion is boiled over a moderate fire, till the third part of the fluid be evaporated. It is then suffered to stand for three or four days, when it is filtred through blotting-paper, and preserved for use, in close vessels. There is no occasion for adding any gum-arabic,which only tends to suspend impurities, while it changes the ink to a pale purple shade. - Another mode of making red-ink, consists in triturating the whites of four eggs, and a tea-spoonful of pounded lump-sugar, with a similar quantity of spirit of wine, till they acquire an uniform consistence. Vermilion is then to be incorporated in such a proportion as will produce a red colour of sufficient strength. The liquor must be kept in a well-closed vessel, and agitated every time before it is used.