23rd June 1503. Alum.

Henry VII had enriched himself by trading alum in 1486, after alternative sources from the Ottoman Empire had been found. Previously the pope had controlled a monopoly being mined only in Tolfa, Italy, in the process making a fortune for the Pope. 

The chemistry of textile dying, which required alum, developed from unforeseen circumstances relating to the Treaty of Betrothal of Henry VIII to Catherine of Aragon, which took place Today in 1503.

Alum Crystal.

However at the time of Henry’s annulment of the marriage, the pope who had controlled the source of alum, essential as a mordant in cloth dyeing, in retaliation, cut off supplies.

Remains of alum liquor channel.

Abandoned Alum House in North Yorkshire..

Alum is a mordant which binds the dye, like a glue, to the cloth fibres, without which the colours are less vivid and soon wash out. Thus without the Papal alum, the race was on to find alternative sources in Britain. 

It was textile manufacturer Sir Thomas Challoner in 1600 who realised, after visiting Italy,that the shales in North Yorkshire, were similar to those at Tolfa.

So returning with key workers he set about quarrying the grey shale from the cliffs on the coast at Ravenscar, North Yorkshire.(1) 

The industry was to continue in Yorkshire until the mid-1800.s and the remains of track-ways for horse and carts, and harbours, where flat-bottomed ships berthed, are still evident.

The shale was roasted slowly for nine months on a bonfire and either toasted seaweed and ammonia from stale human urine was added.

It has been said that ‘Taking the P***’, came from ships’ captains transporting urine from London, when asked the contents of their cargo.

The liquor collected in big lead pans until a fresh chicken’s egg just floated on the surface. After a long time cooling, out came beautiful colourless crystals of pure alum.

Chemistry as a science was not officially developed for another 150 years, but this blend of alchemy and trial and error became the first chemical industry in the country.

Over the next 250 years thousands of tons of alum were made in north Yorkshire all resulting from the rift of Henry VIII from Rome.

Alum was vital to our woollen trade originally based in the West Country, East Anglia, and Coventry where  textiles at the Whitefriars had flourished since the 1340.s, (with its ‘true blue’ dyed cloth), thus establishing the fourth largest industry outside London.

(1) The names Alum Bay in the Isle of Wight and Alum Chine in Dorset testify to the activity there to find alum.


bbc.co.uk.coast-walks.north yorkshire.

wikipedia.org.alum/Pic of crystal.





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About colindunkerley

My name is Colin Dunkerley who having spent two years in the Royal Army Pay Corps ploughed many a barren industrial furrow until drawn to the 'chalk-face' as a teacher, now retired. I have spent the last 15 years researching all aspects of life in Britain since Roman times.

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