If you wander through the highways and byways of Cornwall you may well come across the name Blowing House. Where does this come from? In former times ‘houses’ were built to smelt tin, transforming tin ore, or ‘black tin’, containing other chemical elements such as oxygen or sulphur, into purer ‘white tin’. Stannary law stated that all Cornish tin had to be smelted in Cornwall. The result was a rash of small blowing houses. In these, a charge of black tin and charcoal was kept to a temperature sufficiently hot by bellows, operated by a water-wheel.
From 1700 to the 1850s blowing houses were gradually superseded by reverberatory furnaces. These used coal rather than charcoal but, more importantly, kept the heat source separate from the tin ore, resulting in less loss and contamination of the smelted tin. The first reverberatory furnace in Cornwall was established at Newham, just outside Truro. Tin smelting houses needed to be close to a coinage town (before 1838 when coinage was abolished), near to estuaries or the coast for the import of coal and bricks, and near a source of water-power to run the stamps used to break up slag for re-smelting.
Because of the need for large amounts of coal – at least a ton was required to reduce a ton of black tin – tin smelting was dominated by those with capital – merchants and landowners who could afford the cost of importing fuel. Sometimes they also advanced money to the mines, on the security of the tin ore that would result, thus becoming bankers. The clearest example was the Bolitho family of the Penzance district. Their control of Chyandour smelting house from the 1760s eventually led to the foundation of the Mount’s Bay Commercial Bank in 1807 which ultimately became part of Barclays.
Workers in tin smelting houses were less fortunate. The average wage of the 15 men employed at Chyandour in 1883 was 19 shillings a week, around the same or maybe slightly higher than the average Cornish labourer’s weekly earnings of the time.
With the extension of the railway after the 1830s, a location near the ports became less critical. Seleggan tin smelting works at Carnkie near Redruth began to smelt tin in 1887 and became the largest such works in Cornwall. By 1923 it was the only Cornish tin smelter left operating. In the late 1920s it was employing around 200 people in a continuous three shift system. The works closed in 1931 in the midst of the economic depression.