Copperworks no. 2 in Kaifeng, China

Journal of the Historical Metallurgy Society, 1995, 29.2: 113-116. [Published 1997].

Donald B. Wagner

Kaifeng is a small provincial city in the province of Henan in central China. It was the capital of China in the Northern Song period (960-1127), and the capital of Henan in the early twentieth century, but today its glory is entirely in the past. Unlike almost all Chinese cities it has not grown significantly in recent times: its population was about 200,000 in the 1920’s, and today is much the same. The city wall, built in the Ming period (1368-1644), is largely intact, and still forms the boundary between urban and rural modes of living. The poverty of all of Henan is apparent here, but is not oppressive, and the marketplace is a lively centre of activity in the evening. Kaifeng gives a feeling that here is what China was like in earlier centuries, and it is surprising that foreign tourists seldom come here.

When I was in Kaifeng for a few days in October 1987, just north of the city I noticed yellow-green smoke climbing in the windless air from the building shown in Figure 1 (photographed on another occasion), and was delighted to discover a traditional copper smelting works, Kaifeng di-er yelian chang. Walking through the gate into a yard surrounded on four sides by buildings, I found the scene shown in Figure 2: a small blast furnace, about three metres tall, in a haze of greenish smoke. A young man named Wang Puli made himself my guide, though his country dialect and my imperfect spoken Chinese meant we often had to work to understand each other. Wang Puli explained to me that the blast furnace was to be blown out that evening, Friday, repaired and relined on Saturday, and blown in again on Sunday. I set out by bicycle early Saturday morning because I especially wanted to see the inside of the furnace while it was being relined, but unfortunately lost my way and did not arrive until 10:30 a.m.; by this time the furnace had again been reassembled and loaded with fuel. What could be seen was that the furnace is built of three sections, which can be disassembled using the hoist erected above it. The loaded furnace is seen in Figure 3; the object on the left which resembles an elephant’s trunk is the blast pipe leading from an electric blower.

Blowing-in began on Sunday at 8:00 a.m., when the load of coke in the furnace was ignited through the taphole, the blast was started, and the taphole was sealed with clay. As can be seen in some of the photographs, the blast-pipe blows through the blast-hole from a distance of 10-15 centimetres: it is not attached to the furnace and there is no tuyère. Figure 4 was taken during this blowing-in period.

Coke was added to the charge several times during the blowing-in. The first ore briquettes were added at 8:25, and by 9:00 operation had become regular, with ore briquettes, some large chunks of ore, and coke being charged about every 10 minutes. Wang Puli told me that the ore briquettes were composed of borax, gypsum, limestone (he showed me the labelled bags of these ingredients), and an ore mineral called qingshi . There was no smell of sulphur, so this is presumably a non-sulphide ore. The slag hole was kept open and a trickle of slag ran constantly out, as can be seen in Figure 5. When cold the slag was glassy and had a reddish-orange colour. Occasionally some quartz or flint was added to the charge, presumably to adjust the composition of the slag and keep it flowing freely.

The furnace-master spent most of his time watching conditions in the furnace through the blast hole and adjusting the exact direction of the blast, as can be seen in Figure 6. Copper was tapped three times in the first three hours. As shown in Figures 7-10 the clay seal on the taphole was broken, allowing the copper to flow into a ladle which was then poured into four iron bar-moulds. Two men poured while a third used a long-handled tool to keep back the slag floating on the metal; it can be seen in Figure 10 that some of the slag was not liquid but came out in a large clump.

Friday's production lay in a storehouse, and consisted of 23 bars, a typical one of which weighed 16 kg, i.e. about 368 kg in all. They had a blistered appearance on top. Wang Puli told me that normal daily production is 400-450 kg, but I was unable to find out the end use of the copper.