Or Iodine Scarlet, is an iodide of mercury, having the body and opacity of vermilion, and being as much inferior to it in permanence as it is superior in brilliancy. Of all artistic pigments, it is at once the most dazzling and the most fugitive, and should have no place on the palette. If used, it should be with an ivory knife, as iron and most metals change it to colours varying from yellow to black; hence it should never be compounded with metallic pigments. So sensitive, indeed, is it to the slightest touch of metal, that it has been known to turn to a dull brown merely by being washed over with a colour which had been taken out of its saucer with a penknife. In the cake, it must be carefully kept wrapped up in paper, otherwise the presence of metal tubes or a knife in the colour-box may spoil it. By a foul atmosphere, the scarlet is soon utterly destroyed, and even metallized. In contact with the air, it quickly fades away; and has been found to vanish completely, when exposed to light alone. Employed in water, a thick glaze of gum-arabic or gamboge adds to its stability. As a landscape pigment, the colour is out of the general scale of nature; but in flower-painting its charms are almost irresistible. Nothing certainly can approach it as a colour for scarlet geraniums, but its beauty is almost as fleeting as the flowers.
87. RED CHROME,
Also called Scarlet Chrome, is a bright chromate of lead of an orange-red colour, the red being predominant. Rank in tone, it is liable to the changes of the yellow chromes, though in a less degree. The recent introduction of cadmium red renders the use of this unnecessary.
88. RED LEAD,
Minium, or Saturnine Red, is an ancient pigment, by some old writers confounded with cinnabar, and termed Sinoper or Synoper. It is an oxide of uncertain composition, prepared by subjecting massicot to the heat of a furnace with an expanded surface and free accession of air. Of a scarlet colour and fine hue, it is warmer than common vermilion, whose body and opacity it possesses, and with which it was once customary to mix it. Bright, but not so vivid as the iodide of mercury, it is more durable, although far less so than vermilion. When pure and alone, light does not affect its colour, which soon flies, however, on being mixed with white lead or any preparation of that metal. By impure air, red lead is blackened and ultimately metallized.
On account of its extreme fugacity when compounded with white lead, this red cannot be used in tints; but employed, unmixed with other pigments, in simple varnish or oil not rendered drying by any metallic oxide, it may stand a long time under favourable circumstances. It is an excellent dryer in oil, and has often been used as a siccative with other colours, but it cannot safely be so employed except with the ochres, earths, and blacks in general. Oils, varnishes, and, in some measure, strong mucilages, are preventive of chemical action in the compounding of colours, by intervening and clothing the particles of pigments; and hence heterogeneous and injudicious tints and mixtures have sometimes stood well, but are not to be relied upon in practice. Altogether, red lead is a dangerous pigment in any but skilled hands, and has naturally had a variable character for permanence. It is frequently adulterated with earthy substances, such as brickdust, red ochre, and colcotha.
VERMILIONS.
Vermilion is so called from the Italian word vermiglio (little worm,) given to the kermes or "coccus ilicis," which was used as a scarlet dye before the introduction of cochineal. It is a sulphuret of mercury, which previous to levigation is called Cinnabar; and is found native in quicksilver mines, as well as produced artificially. This is an ancient pigment, the κιννάβαρι of the Greeks, and the minium—a term now confined to red lead—of older writers. Pliny states that it was so esteemed by the Romans, as to have its price fixed by express law of state. Among other places, the natural product is met with in California, Spain, and Peru; and in China there is a native cinnabar so pure as only to require grinding to become very perfect vermilion. Whether the natural possesses any advantages over the artificial, appears to admit of doubt: Bouvier thought that the former blackened more than the latter, and others coincide with him. As, however, native vermilion has become commercially obsolete, the question of their comparative permanence is of little importance. Theoretically, it is difficult to assign a reason why there should be any difference between the two.
Vermilion is capable of being made by both wet and dry processes, but the last are almost exclusively adopted on a scale, and are, we believe, preferable. Our opinion, expressed with some diffidence, is, that pigments whose colour depends on the union of sulphur with a metal—such as vermilion and cadmium yellow—are more stable when the sulphur is forced to bite into the base. This can only be effected by a considerable degree of heat, far greater than can be obtained in any moist method. We hold that in pigments so produced, the sulphur is less liable to oxidation by air and light, and that therefore the colour better withstands exposure to those agents. Before now, vermilions have been taxed with fading in a strong light: supposing them genuine, it would be interesting to know by what mode they were manufactured.
There are two kinds of vermilion in common use, European and Chinese, of which the first inclines to orange and the second to purple. These include the several varieties known as—Vermilion, Deep Vermilion, Pale Vermilion, Scarlet Vermilion, Chinese Vermilion, Carmine Vermilion, Extract of Vermilion, Orange Vermilion, and Field's Orange Vermilion.