Agricola watches a smelting furnace with a notebook in his hand.

The four elements at the smelting furnace

Georgius Agricola (1494–1555) was a German physician and scholar who described the mining and metallurgical practices of his time. In the ninth book of De Re Metallica he takes the reader to a smelting furnace. Governing the four elements sounds like an ambitious claim. Agricola unfolds it into a series of decisions an experienced smelter has to make in the course of a working heat.

What the smelter watches

A man who knew how to mix the four elements rightly has always been counted among the foremost smelters. He mixes them rightly when he casts no more ore, which partakes of earth, into the furnace than is fitting, pours in water whenever it is needed, skilfully governs the blast of the bellows, and casts the ore into the part of the fire that burns bright.

– Georgius Agricola, De Re Metallica, 1557, p. CCCXVIII.[1]

With ore, the first consideration is quantity. A larger charge is hardly always better, since the furnace must be able to handle it. Water also has to be supplied in due measure. Air, in turn, has a direction and a speed. By working the bellows the smelter alters what happens in the fire. Even a well-fed furnace is hotter in some places than in others. Among the worker’s skills is knowing where to put the ore so that the heat will do its work.

Finding the right place in the fire

Earth, water, air and fire stand side by side in the sentence. In the workshop they come into view in different ways. Earth arrives with the ore, air reaches the furnace through a tool, and the fire has regions of differing strength. A visitor might first notice the flame. Agricola also directs attention towards the smelter’s less conspicuous decisions. What ultimately comes out of the furnace depends on the charge, the draught and the position of the heat being right for one another at a particular moment.