Dhan had constructed a smelting furnace

Over a shallow hole in the ground Dhan had constructed a smelting furnace, a clay wall surrounded by a thicker outer wall of rock and mud, the whole girdled with bands of sapling. It stood the height of a man's shoulders and a pace wide, tapering to a slightly narrower diameter at he top to concentrate the heat and reinforce the walls against collapse.

In this oven Dhan made wrought iron by burning alternating layers of charcoal and Persian ore, pea and nut size. Around the oven a shallow trench had been dug. Sitting on the outer lip with his feet in the trench, he operated bellows made from the hide of a whole goat, forcing precisely controlled amounts of air into the glowing mass. Above the hottest part of the fire, ore was reduced to bits of iron like drops of metal rain. They settled through the furnace and collected at the bottom in a blob-like mixture of charcoal, slag and iron, called the bloom.

Dhan had sealed a removal hole with clay that he now broke away so he could drag out the bloom, which was refined by strong hammering requiring many reheating in his forge. Most of the iron in the ore went into slag and waste, but that which was reduced made a very good grade of wrought iron. But it was soft, he explained to Rob through Harsh. The bars of Indian steel, carried from Kausambi by the elephants, were very hard. He melted several of these in a crucible and then quenched in fire. After cooling, the steel was extremely brittle and he shattered it and stacked it on pieces of the wrought iron.

Now, sweating among his anvils, tongs, chisels, punches, and hammers, the skinny Indian displayed biceps like serpents as he wedded the soft and hard metals. He forge-welded multiple layers of iron and steel, hammering as if possessed, twisting and cutting, overlapping, fording the sheet and hammering again and again , mixing his metals like a potter wedging clay or a woman kneading bread.

Watching him, Rob knew he could never learn the complexities, the variables needing subtle skills passed down long generations of Indian smiths, but he gained an understanding of the process through asking innumerable questions.

From the book “The physician” by Noah Gordon.