The Alum Industry : In-depth Information

Alum was principally used in the textile industry as a fixing agent for dyes. It was also used by tanners to produce a more supple leather.

The process involved in extracting alum from alum shale was long and complicated. The shale was first quarried from inland hillsides, such as Belman Bank, Guisborough or coastal cliffs, such as Boulby, leaving massive quarries scarring the landscape.

The shale was then heaped into large mounds (often up to 30 metres high), fired and left to smoulder for up to 9 months. The roasted shale was then tipped into leaching tanks where it was left to soak in water.

The solution, containing aluminium sulphate (the active ingredient of alum), was then drained off and ran along stone or wooden conduits to the ‘Alum House’. Here the water was boiled away from the solution in evaporating pans.

An alkali, derived from human urine or burnt kelp, was added to cause precipitation of the alum crystals. The crystals were then bagged and transported for sale. The burnt shale left in the leaching pits was either disposed of nearby to form enormous shale tips (inland sites) or simply thrown in to the sea (coastal sites).

The Alum Industry

In-depth Information