Alum in Yorkshire – the first chemical industry

One of our local volunteers has written an article to give you an introduction to Alum. Come and see some real alum at the museum - and a unique urine barrel...

Alum was used as a mordant or fixative for dyes in the textile industry, for waterproofing leather, in the manufacture of parchment, glass and candles, and as a fire-retardant. As a fixative for natural dyes it was essential to allow the finery of the Church, the crown or the court to be distinctive from the drab colours of the masses! 

Alum had been found naturally in the eastern Mediterranean in Roman times, but by the 15^th century was being produced in Italy, with the Vatican controlling most of the supply. It was thought necessary to try to establish an English alum industry, especially after Henry VIII’s split with Rome. There are stories of Sir Thomas Chaloner kidnapping or smuggling key workers at the Vatican out of Rome in barrels, for which apparently, he was excommunicated. 

In the 16^th century there were various failed attempts to establish an industry on the south coast, but around 1600 the first successful alum works were established near Guisborough, and during the 17^th century about 20 works were established at various sites in land and on the Yorkshire coast. By the 1830s of the five works still operating four were local to Staithes, at Loftus, Boulby, Kettleness and Sandsend all with access to sea-borne transport. As synthetic ways of manufacturing alum were found in 1845 the traditional manufacturers struggled economically and the last works closed in 1871 at Sandsend. 

For over two hundred and seventy years the alum workers of Yorkshire had conducted the lengthy, complex and multiple phases of production, and established the first major chemical industry. Chemically the product was potassium ammonium alum, but the producers got to this end without knowing the chemical formula. The process involved:

• Clearing the unwanted earth above the shale

• Quarrying the alum shale – about 72 tons for every ton of finished alum

• Calcining or burning the shale – the piles could reach 100 feet high and smoulder for up to a year

• The ash was washed in steeping pits outside

• The waste was dumped, the liquor left to clarify in the alum house

• Water content was evaporated by heating

• An alkali was added 

• Alum crystals were separated from the mother liquor

• The crystals were washed, and then

• Placed in roaching casks, which when dismantled left pillars of alum 

• Alum was then sold as powder or in lumps.

  
  

The local shale was particularly suited to the task as it contained elements of carbon, which helped the piles burn, but imports of coal and alkali, and places to collect the water needed for the process were also wanted. The alkali came in the form of seaweed, which was cut, dried, burnt and compressed into a ‘cake’ of potash, or in urine, which was collected in the village, but also brought in ship loads from Newcastle and London (‘you must be taking the piss’!). The stink from the process was unbearable; an attempt to set up an alum works in London produced dead fish in the Thames, ‘loathsome vapours’ and acid rain, but such side effects were acceptable up north! 

Besides the stink makeshift harbours were built below the cliffs, local workers had an additional source of meagre pay for extremely hard labour, and the landscape was transformed. What remains now below the cliffs at Boulby and Kettleness are piles of grey moonscape shale upon which nothing has grown in the 150 years since the works stopped producing. Old alum workings can also be seen just north of Sandsend from the Cleveland Way that runs there along the old railway line. At Alum House in Boulby there is a tunnel that descends to the foreshore 200 feet below, a tunnel, and the remains of a tunnel and post holes from the old dock from whence the alum was exported.