A variety of yellow and red ochres, in addition to the pigments above mentioned, were used by painters, such as rubrica, an iron ochre of a dark red colour, and sinopis, or reddle, obtained from Egypt, Lemnos, and the Balearic Isles. Oxides of manganese were used as brown pigments. The white pigment, paratonium, was probably meerschaum. Melinum was a variety of chalk found in Samos. The ancients were well acquainted with indigo and madder, and with the method of manufacturing lakes, which was employed by Grecian artists.
The famous purpurissum was chalk or clay stained by immersion in a solution of Tyrian purple. Atramentum was lamp-black: ivory-black was used by Apelles, and was known as elephantinum. The ink of the ancients consisted of lamp-black suspended in a solution of gum or glue. The atramentum indicum, imported from the East, was identical with China ink.
The ancients were well skilled in the art of dyeing, and even of calico printing. The Tyrians produced their famous purple dye as far back as 1500 B.C. It was obtained from shell-fish, mainly species of Murex, inhabiting the Mediterranean. Tyrian purple has been shown to be dibrom-indigo, and to have been produced by the action of air and light upon the juices exuded from the shell-fish. The fine linen of the Old Testament was probably cotton, for the production of which Egypt was long celebrated. That the Egyptians were acquainted with the use of mordants seems evident from the following passage from Pliny, quoted by Thomson:—
There exists in Egypt a wonderful method of dyeing. The white cloth is stained in various places, not with dye stuffs, but with substances which have the property of absorbing colours; these applications are not visible upon the cloth, but when they are dipped into a hot caldron of the dye they are drawn out an instant after dyed. The remarkable circumstance is that, though there be only one dye in the vat, yet different colours appear upon the cloth; nor can the colour be afterwards removed.
This passage accurately describes the process of madder dyeing on cotton, whereby a variety of fast colours—reds, browns and purples—can be obtained from the same vat by the employment of different mordants, such as alumina, oxide of iron, or oxide of tin, etc.
Glass has been known from very early times. Representations of glass-blowing were found on the monuments of Thebes and Beni Hassan, and large quantities of glass were exported to Greece and Rome from Egypt, mainly by Phœnicians. Aristophanes mentions it as hyalos, and speaks of it as the beautiful transparent stone used for kindling fire. The Egyptians made use of various metallic oxides in colouring glass. The hæmatinon of Pliny was a red glass coloured with cuprous oxide. Cupric oxide was used to colour glass green; and ancient blue glass has been found to contain cobalt. The costly vasa murrhina of the Romans, obtained from Egypt, probably consisted of fluorspar, identical with the Blue John of the Derbyshire mines.
Stoneware has been made from time immemorial, and the Chinese have manufactured porcelain from very remote periods. Bricks and tiles were made by the Romans, and mortar and stucco were employed by the ancient Egyptians.
Soap (sapo) is mentioned by Pliny, but its detergent properties were apparently unknown to him. It appears to have been first made by the Gauls, who prepared it from the ashes of the beech and the fat of goats, and used it as a pomatum, as did the jeunesse d’oreé of Rome. Wood ashes, as well as natron, were, however, used by the ancients for their cleansing properties.
Starch, acetic acid, sulphur, alumen or crude sulphate of alumina, beeswax, camphor, bitumen, naphtha, asphalt, nitrum (carbonate of soda), common salt, and lime, were all known to the Egyptians, and were used by them for many of the purposes in which they are employed to-day.
It will be evident from this brief survey that the ancients possessed a considerable acquaintance with many operations of technical chemistry; but, although they must necessarily have accumulated a large amount of knowledge, very little has come down to us concerning the mode in which their processes were conducted, or as to the precautions they employed to ensure uniform results. Their methods were probably jealously guarded and handed down by successive members of the crafts as precious secrets. The experienced masters of these crafts must have met with many strange and perplexing phenomena in the course of their operations, and a spirit of inquiry must thereby at times have been awakened. But, under the conditions in which their industries were prosecuted, the scientific spirit was not free to develop, for science depends essentially upon free intercommunication of facts and the spread of knowledge of natural phenomena. Moreover, the great intellects of antiquity, for the most part, had little sympathy with the operations of artisans, who, at least among the Greeks and Romans, were, for the most part, slaves. Philosophers taught that industrial work tended to lower the standard of thought. The priests, in most ages, have looked more or less askance at attempts, on the part of the laity, to inquire too closely into the causes of natural phenomena. The investigation of nature in early times was impossible for religious reasons. There was an outcry in Athens when the thunderbolts of Zeus were ascribed to the collision of clouds. Anaxagoras, Diogenes of Apollonia, Plato, Aristotle, Diagoras, and Protagoras were charged by the priests with blasphemy and driven into exile. Prodikos, who deified the natural forces, as did Empedokles the primal elements, was executed for impiety. Sacerdotalism in Athens had no more sympathy with science than had the Holy Congregation in Italy when it banned the writings of Copernicus, Kepler, and Galileo, and sent Giordano Bruno to the stake. The educated Greeks had no interest in observing or in explaining the phenomena of technical processes. However prone they might be to speculation, they had no inclination to experiment or to engage in the patient accumulation of the knowledge of physical facts. “You Greeks,” says Plato in one of his Dialogues, “are ever children, having no knowledge of antiquity, nor antiquity of knowledge!” The influence of a spurious Aristotelianism, which lasted through many centuries and even beyond the time of Boyle, was wholly opposed to the true methods of science, and it was only when philosophy had shaken itself free from scholasticism that chemistry, as a science, was able to develop.