The Romans were the first to use brass on any significant scale, although the Greeks were well acquainted with it in Aristotle's time (c. 330 B.C.). They knew it as 'oreichalcos', a brilliant-and-white copper, which was made by mixing tin and copper with a special earth called 'calmia' that came originally from the shores of the Black Sea. Pure zinc was not known until quite modern times, the ore employed being calamine which is an impure zinc carbonate rich in silica. The earliest brass was made by mixing ground calamine ore with copper and heating the mixture in a crucible. The heat applied was sufficient to reduce the zinc to the metallic state but not to melt the copper. The vapour from the zinc, however, permeated the copper and formed brass which was then melted. (10).
In historical records, the word 'brass", like 'bronze", must not be taken too literally, but should be interpreted according to the known metallurgy of the times. Brass is frequently mentioned in the English version of the Bible, although so far as the Old Testament is concerned, the word probably referred to copper or bronze. In the New Testament, 'chalkos' means copper or bronze.
Some Roman armour, particularly the helmets worn on ceremonial occasions, was made of brass (Fig. 5).
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| Figure 5. Examples of Greek bronze work. The head is thought to be that of the poet Sophocles and dates from about the 2nd Century B.C. On the left is an inscribed bronze mirror-cover showing Aphrodite and Pan. | |
A large number of fine specimens of these helmets still survive. Spears and swords, daggers and palstaves, were originally of bronze, but later for weapons the Romans turned entirely to iron.
The Romans also used brass for brooches (fibulae), personal ornaments and for decorative metalwork. The alloys employed contained from 11 to 28 per cent of zinc, and the Romans clearly knew the value of different grades of brass for different purposes. The quality specified for delicate decorative work, for instance, had to be very ductile and of a good colour; and the Roman mixture contained about 18 per cent of zinc and 80 per cent of copper, i.e. it was about the same as the modern 'gilding metal' so widely used today for imitation gold jewellery.