1. Metals in the Roman
World
Geoff Tindall
Session 7 -2012

2. Metals of the ancient world
Gold, Silver, Copper, Lead, Iron, Mercury, Tin, Zinc,
Antimony and Arsenic.
Of these only one was usually found native, the others
were primarily made from ores.
From these metals important alloys were made
Bronze (80-90% Copper, 10-20% Tin)
Brass (80-90% Copper, 10-2% Tin, 2% Zinc)
Pewter (85-90% Tin, remainder Copper)
Solder (70-90 % Lead with Tin or Antimony)
Steel (Iron with 0.2 – 1.3 % carbon

3. Primary minerals in ores
are
Malachite – Cu2CO3(OH)2
Galena – PbS
Cinnabar – HgS
Cassiterite – SnO2
Magnetite – Fe3O4
Hematite – Fe2O3
Goethite - FeOOH

4. Roasting and Smelting
(Base Metals: Copper, Lead, Tin, Zinc, Mercury)
Roasting is just heating up the ground rock and blowing
air in to it through a tuyere (clay pipe), this gets the sulfur
out of the rock
PbS +3O2 -> PbO + SO2
Smelting is the next stage which is to heat the oxide with
charcoal in a furnace and a chemical reaction makes
metal. PbO + C -> Pb + CO2
The fire is hot so liquor metal flows to the bottom,
unreacted rock (slag) floats to the top

5. Blooming and Forging
The romans did not have the technology to make a fire hot
enough to smelt or cast iron so when the iron was
reduced it formed a ‘bloom’. Which is a sponge like
material.
The bloom was then forged or wrought, that is heated up
in a fire and hit with a hammer until it became one piece.
By putting iron in a fire with coals and hitting it, carbon
becomes included into the metal structure as ‘pearlite’
crystals and steel is formed. The more it is worked, the
more carbon is included and better steel is made.
Ancient steel was highly variable, and good smiths were
attributed magical abilities.

6. Did iron supersede bronze
The ancients could not cast iron, but bronze casting is
easy, so bronze objects could be made in a way iron could
not.
Iron is soft and not ductile, so does not make good tools
or weapons. Steel superseded bronze for these
purposes, not iron.

7. What about silver ?
Silver is often associated with
lead geologically, so a process
called cupellation was used to
separate lead metal from silver
metal.
Pb + Ag + O2 -> PbO2 + Ag
By heating lead and silver
mixture and blowing in air, then
lead can be converted back to a
rock like substance, and liquid
silver separated from it. The
lead was not recoverable from
this process.