THE NORTH RIDING PROJECT

Alum was extracted from quarried shales through a large scale and complicated process which took months to complete. The process involved extracting then burning huge piles of shale for 9 months, before transferring it to leaching pits to extract an aluminium sulphate liquor. This was sent along channels to the alum works where human urine was added. At the peak of alum production the industry required 200 tonnes of urine every year, equivalent to the produce of 1,000 people. The demand was such that it was imported from London and Newcastle, buckets were left on street corners for collection and reportedly public toilets were built in Hull in order to supply the alum works. This unsavoury liquor was left until the alum crystals settled out, ready to be removed.

National Trust

What a preposterous, obscure and infernal business alum-making was. The boiling of stale urine and burnt seaweed ash, and that mysterious matter – the alchemical secret – of the floating egg. Someone hazarded dropping a hen’s egg into the solution, and found that when it floated the solution was ready to be harvested. All this was carried out in remote clifftop hamlets, hovels cheek-by-jowl with the reeking works

Guardian