Studies into the Discovery and Exploitation of Metals.
Work on this topic has been presented in some detail in three Monographs (links below), so this page serves as more general background to the work and its direction.
The prehistoric discovery and exploitation of metals was perceived as being an important part of the economy of the Metal Ages. In line with the experimental procedures promulgated at Butser, the work began with the development of a construct based on excavated, supposedly metal producing, furnaces. The construct and the way in which it was operated leaned heavily on late 19th century technology, considered more pertinent than the innovative, chemical and electrical methods adopted in the 20th century.
The early work proved largely unsuccessful and when the author of the Monographs retired he offered to review the programme. He rapidly concluded that there were a number of flaws in the foregoing:-
(a) Degrading recent technology can only go so far before a step change is reached. There is usually no clear indication of what the situation was before then. For example, the discovery of metals and the availability of bellows and "bulk" chemicals cannot be coeval. How they relate to one another cannot be resolved by retrogression.
(b) The interpretation of excavated archaeological remains is less than clear cut :-
(1) It is often difficult to be sure of the use of discovered furnaces.
(2) "Technological persistence", i.e. the continued presence of features once thought useful, may lead to the presence of irrelevant elements, which at worst may have proved harmful to the process as operated.
(3) In earlier periods, when all was empirical, a knowledge of a way to make metals was an important bread-
(4) However, such empirical knowledge does leak out, co-
Faced with these problems, it was decided to adopt a radical new approach. Instead of working back from the present, it was decided to work from the past forward to the present. This threw up a new problem. How could the beginning be identified?
It was regarded as permissible to use present understanding and knowledge to define the factors that had to come together to produce a recognisable metal.
These are :-
(a) Ore, in its oxide form, reasonably finely divided (for quick reduction) and pure ( if impurities cannot be melted away, they will degrade any metal produced).
(b) A controlled source of an appropriate, high temperature.
(c) A controllable reducing atmosphere.
(d) Some means of stabilising any metal formed.
An underlying question arises, as to why mankind should be interested in and involved in manipulating ores, in the first place. The only clear answer appears to be colour.
Mankind has always seemed interested in pigments and certainly long before the appearance of metals, for example cave paintings and later with pottery glazes. Today, body colouring is still prevalent and surely existed for most of time.
To make a good pigment from a coloured ore, it needs to be pure and finely divided. Manual grinding of dense ores is hard labour and this may have led to producers (for sale or barter, rather than simply for personal usage) to turn to heat as a way to assist the process. Heating and shattering with cold water is quite a widespread procedure.
Thus pigment makers would readily satisfy one of the first requirements identified.
Pottery makers could have provided all the other requirements.
It was postulated that pottery kilns when operated at maximum thermal efficiency could convert ore to metal. It is therefore proposed that sooner or later, someone would use a pottery kiln to prepare ores for pigments and thereby stumble on metal.
This approach was found, by experiment, to be highly successful and the work at Butser has shown it is possible to use a wood fired pottery kiln to produce all the metals known in antiquity -
It has also been shown that the pottery kiln could be evolved into the shaft furnace, first with an external wood fire, and then with internal charcoal firing. Until this last was developed, iron could not be produced reliably and this may explain the late arrival of the Iron Age, which really requires bulk availability of charcoal and the use of bellows.
The fact that copper is difficult to melt and thereby to free it from impurities was shown to be resolved by extracting it into lead and recovering it as lead bronze. This may explain the rapid dominance of the Bronze Age over any Copper Age.
Another area of study has shown the bowl furnace, originally a melting tool, has smelting capability and is related to the African furnace.
The work at Butser has been largely qualitative showing that the route to metals outlined above is feasible. It was planned to carry out quantitative work.
Sadly, Tony Hamlin, the author of this work died in January 2000.