Classical Studies 2700B

Other types of metal handling (continued from previous lecture, and all illustrated with slides):

d) Lost wax (cire perdu) casting: a difficult method of producing metal objects, but result often v. attractive. Model of object is made, with great detail, of wax. It is then provided with wax branches and submerged in a container of plaster-of-Paris; when plaster has set, the wax is all melted out of the plaster through heating in an oven or fire; molten metal is then poured into the plaster mould; after metal has cooled, plaster is broken away and resulting metal object should (!) resemble exactly the original wax image;

e) granulation: tiny balls of gold applied to surface of object and then fused into place by high temperature heating; this is done today with a propane torch; but how Egyptians, Minoans and Etruscans did this in antiquity is not properly understood;

lastly, two techniques from the New World:

f) depletion gilding: “all that glisters is not gold”; this technique treats a metal sheet made of 60% copper, 20% silver and 20% gold and ends up with a gold surface by getting rid of the copper and silver in the surface layer;

g) sintering: how to incorporate a material that cannot be melted by using another as a kind of glue; ex. from Ecuador of gold dust and platinum (which latter has a melting point of 1650° C; and ancient furnaces could not reach this temperature).

IRON

Of the various iron ores, oxides were the most commonly used in ancient times, though some carbonates used as well (processes are essentially the same). Meteoric iron (iron-bearing meteors are called siderolites) was the first kind known: Sumerians called it the “heavenly metal” and it was comparatively rare. Great problems in smelting iron: melting point of pure iron is c. 1635° C and ancient furnaces could reach only c. 1300° C at best; so no pig iron or cast iron in antiquity. Since melting temp. of iron lowers as it absorbs carbon, what was produced was either wrought iron or, if it was carburised, a form of steel. Description of production of a bloom of iron in a furnace. Processes are known from modern experiments with replicas of Roman furnaces; it took about 8 hours to produce c. 9 kg (20 lbs) of metal.

History of iron smelting is somewhat mysterious: from c. 2,700 BC objects of smelted iron turn up in small amounts quite widely in Middle East, but no evidence (yet) of furnaces (in fact, earliest remains of an iron smelting furnace are from Hüttenberg in Austria—c. 500 BC). Earliest more or less regular production of iron was done by the Hittites in Asia Minor from around 2,000 BC; earlier, iron may have been a fortuitous by-product of copper smelting. However, only after the collapse of the Hittite empire (c. 1200 BC) is there upsurge of iron production in Middle East and also in Greece and then later in Italy. Also, for handling a metal that could not be melted or cast, new techniques were necessary—tongs, anvils, hammers. Iron is called the “democratic metal”—fairly plentiful and relatively cheap: initially used almost exclusively for weapons, but by 500 BC in Greece artisans (stone masons and woodworkers) had tools made of iron and this had great effect on output, techniques and quality. Ironworking had reached Britain by 500 BC (Celtic Hallstatt culture) and great variety of techniques evolved for handling the material; ex. of “faggoting” (a sort of lamination or layering of carburised and uncarburized iron), good for blades or for tires on chariot wheels and carts. Iron soon replaced bronze for everyday objects.

Finally, some evidence for deliberate steel-making in Alpine areas to the N. of Italy (Noricum and Bohemia); also, in Hyderabad in India there was made what the Romans called “Seric iron”.

Roman Blacksmithing: see this handout, which will be discussed briefly in class, if there is time available. Sources of information about the work of Roman blacksmiths. They wear something like a uniform. Note the hearth, the bellows, the fuel (charcoal), and the tools for the hearth; the anvil (different shapes and sizes); tongs and hammers; chisels and punches; nail heading tool. Also “fancy work”—parade armour and the like: usually done in specialist shops; but expendable stuff (spear heads, arrow heads and artillery bolts) were made by blacksmiths in military camps.