In the production of bronze, they used to mix oxydated tin ore, in the proportions which experience had taught them, with oxydated copper ore or copper pyrites; to this mixture was added a small quantity of charcoal. The whole was placed in an earthen vessel in the midst of a burning furnace. The two oxides were reduced to a metallic state by means of the charcoal; the copper and tin being set free, blended and formed bronze.
When the alloy was obtained, all that was necessary was to dip it out and pour it into sand or stone moulds which had been previously arranged for the purpose.
The art of casting in bronze must have played a very essential part among primitive peoples. There was no instrument that they used which could not be made by casting it in bronze. The sword-blades were thus made; and, in order to harden the edge of the weapon, it was first heated and then cooled suddenly, being afterwards hammered with a stone hammer.
In fig. 147, we represent the workshop of a caster in bronze during the epoch we are considering. The alloy, having been previously mixed, has been smelted in a furnace, and a workman is pouring it into a sand-mould. Another man is examining a sword-blade which has just been cast.
Fig. 147.—A Founder's Workshop during the Bronze Epoch.
Bronze being precious, it is probable that in these ancient communities bronze weapons and implements were reserved for rich and powerful personages, and that stone weapons remained the attribute of the common people. The use of bronze could only become general after the lapse of time.
The high value of bronze would lead to its being economised as much as possible. The Pre-historic Museum at Copenhagen contains unquestionable proofs of this scarcity of the metal, and the means which were used for obviating it. Among the bronze hatchets in the Museum of Copenhagen, there are some which could only have served as ornaments, for they contained a nucleus of clay, and the metal of which they were composed was not thicker than a sheet of paper.
We must also add that worn-out instruments of bronze and utensils which were out of use were carefully preserved in order to be re-cast; the same material re-appearing in various forms and shapes.