Gunpowder and galls

From the 16th century The Blean served two nationally important enterprises, the copperas works at Tankerton and the gunpowder mills of Faversham.

Copperas. London Clay contains brown nodules of copperas or iron pyrites, which are washed out by wave action along the coast. The nodules were collected and placed in long beds on the shore to weather for four years. Inundation of the copperas beds by the sea was a risk and a defensive wall was constructed with layers of faggots held by oak posts. A ditch was created on the landward side and soil heaped over the structure.

The resulting green ferrous sulphate crystals were doubly significant to the economy of Canterbury. Weavers used them as a mordant to bind vegetable dyes to their fabric but they were also combined with gallic acid from oak apples or galls to produce an intense black colour used as an ink by the monks.

The copperas works continued production until 1835.

Gunpowder was made by mixing sulphur with potassium nitrate and charcoal derived from alder, hazel, willow and alder buckthorn. Imported potassium nitrate was expensive but it could be made locally from animal manure mixed with earth, crushed oyster shells and potash obtained by burning beech wood. The Oare Gunpowder works finally closed in 1934 but are once again in operation, though now as a fascinating visitor centre.

With thanks to the Blean Heritage and Community Group