Alum industry in North Yorkshire

For over 250 years, the coastal and moorland areas of North Yorkshire were the centre of the alum industry in England.^[1] Alum was required for tanning, medicines, and most importantly, as a mordant for fixing dye into clothes or cloth, before the industrial revolution allowed dyes distilled from coal, via a sulphuric acid method, to be readily available.^[2][3][4] In the Elizabethan age, most alum was acquired from workings in Italy, and the availability of supply was controlled entirely by the Italians and meant that the supply could be turned off due to political whims; Henry VIII, Edward VI, and Elizabeth I had seceded religiously from Catholicism to form the Church of England.^[5] Sir Thomas Chaloner discovered alum-shale rocks on his estates in Guisborough, and he set about exploiting this resource and received Royal Assent from James I, but after two years of operation, the licence to produce alum passed to the crown.^{[6][note 1]} By the year 1609, a law had been passed prohibiting the import of foreign alum, partly so that it could generate revenue for the crown, but also due to the nature of the strained relations between the recently protestant United Kingdom, and the majority of foreign countries that supplied alum being Catholic.^[9][10] Documents from the era show that in the early years, the hiring of foreign experts to aid with the alum production was necessary, but by the 1630s, the English alum workers were in high demand across Europe and only the intervention of the government prevented those workers from being hired abroad.^{[note 2]}

North Yorkshire became a powerhouse region for the creation of alum and its associated transportation. Other sites were tried throughout Britain, including Lancashire, Dorset, Hurlet in Scotland, Neath in South Wales, and London.^[12] The discovery of alum in Dorset occurred in the 1560s, with licences being granted for the industry there.^[13] The site in London was quite close to the Tower of London and was started during the reign of Charles I, but was suppressed in 1627 due to the "loathsome vapour" that the site produced, and was alleged to have been poisoning the fish in the Thames.^[14]

Alum shales were quarried, then burnt on huge open fires of brushwood, sometimes for up to nine months.^[15] The stacks for burning often were 98 feet (30 m) wide, and 49 feet (15 m) high.^[16] The resulting powder was steeped in tanks of water (lixiviation), which extracted the sulphates of iron, and the pyrites within the shale produced sulphuric acid, which in turn, precipitated the alumina. It could take up to 33–100 tonnes (36–110 tons) of alum shale rock to produce 1-tonne (1.1-ton) of alum.^[17] The liquid was then moved by gravity to the alum house where it was boiled, and the key to the best time to stop heating was to float a hen's egg in the liquor to act as a hydrometer.^[16] When the egg floated to the top of the liquor, it was ready for the boiling to cease, and for the liquor to be separated out.^[18] At this point, the yellow iron silicate (known as Slam) was siphoned off the liquor, and could be sold on to make fertiliser.^[19] Wherever possible, the use of gravity was employed to cause as little effort as possible in transporting the product. Quarries were usually stepped, and the quarried rock was burnt lower down than the quarry face, and when the burnt rock was mixed with water to form the liquor, troughs would then allow the liquor to run downhill to a building known as the alum house for the boiling process.^[20][21] This process of firing, cooling, settling, heating, separating and mixing, has led to it being labelled the first of Yorkshire's dirty industries.^[22] One writer commented that the 80 boiling pans in constant use at Boulby, represented "a true hell's cauldron."^[23] Some accolades have heralded the alum industry in Yorkshire as the first inorganic chemical industry in Britain, but copperas was being worked in Essex and Kent some 25 years before the alum industry took off in Yorkshire.^[24]

The alum industry helped develop the port of Whitby as not only was the finished product stored in "houses" on the quayside, and then exported through the port, but coal had to be brought in for the process.^{[25][26][27][note 3]} A record of ships leaving and entering Whitby harbour in 1612, shows that one particular ship, the Allome An, made four trips to London carrying a total of 217 tonnes (239 tons) of alum. Imported coal, mostly from Sunderland, totalled 667 chaldrons, in a total of 39 inwards sailings throughout the same year also.^{[29][note 4]}

Another important ingredient in the process was the use of human urine as a source of ammonia, which initially came locally from Whitby, and then from Newcastle and Hull, but the amounts supplied proved insufficient (2 tonnes (2.2 tons) of urine was needed to make 1-tonne (1.1-ton) of alum).^[31] The supply chain was switched to London, with collected urine being sent north in tubs. The preferred urine was that from the poorer classes, as they tended to drink beer not wine, the resultant urine was better for the process.^[31][32] This had a secondary benefit in sewage disposal for the City of London, and those supplying the urine were paid for the product.^[33] Alternatively, burnt kelp was used to precipitate potassium sulphate in the process, and whilst local supplies were used, eventually kelp had to be sourced from mainland Scotland and Orkney when the supply derived from the coast of North Yorkshire was not plentiful enough.^[34][35] The need to transport urine, coal and other ingredients in, coupled with the need to export the finished alum, led, in part to the creation of flat-bottomed boats known as "Whitby Cats". Many of the coastal workings were not by a suitable harbour, and so ships would beach themselves at low tide to allow the transfer of minerals.^[36] The transport of goods was limited due to the alum workings all being before the advent of railways in the area;^{[note 5]} historical documents show that coal from the Durham Coalfield was transported through Yarm to feed the works inland via a pannier system, or by ship for the coastal workings.^[34]

The location of alum workings extended from Ravenscar on the coast at its southern extent north-westwards towards Skinningrove, before curving inland at the foot of the Cleveland Hills escarpment, finishing near Osmotherley in the small village of Thimbleby.^[16][38] However, the inland workings were on a smaller scale than the coastal workings; partly due to shale reserves, but also at the time, transportation of the finished product was simpler for the coastal workings as ships could simply moor-up on the beach adjacent, or below the workings.^[16][39] Some sites took advantage of the boats that could beach themselves, others, such as at Saltwick Bay, developed their own harbours to export the alum.^[36] Inland working has one advantage over the coastal areas in that the overburden above the alum shale was said to be thinner and softer making it easier to extract the shale underneath.^[40] In 1769, production of alum across the Yorkshire sites peaked at 6,000 tonnes (6,600 tons) for the year,^[41] however, by the end of the 18th century, alum was selling at £13 per tonne, when it cost £14 per tonne to produce.^[42] The band of alum shale in North Yorkshire is typically 100 feet (30 m) thick, and exists at varying depths. The lower section of shale was not used as it was low on the alumina sulphate and its composition had a greater ratio of bituminous material within it.^[43] Fossils were also found within the shale measures; a huge plesiosur is on display in the Yorkshire Museum in York, and other finds have been an ichthyosaurus, and a teleosuarus (a huge crocodile).^[36] The cap over the alum shales at the coastal workings was usually sandstone, which could be used as a secondary aggregate for building purposes, but it needed care to remove it. In some places, this caused quarrying problems, such as at Kettleness, where the cap is said to have 39 feet (12 m) thick.^[44]

In December 1829, heavy rainfall caused the village of Kettleness to slip into the sea. The inhabitants had taken shelter in a ship, the Little Henry which had come to the coast there to collect alum. The destruction of the village and its alum works delayed alum production for two years, and the quarrying on the coastline was blamed for the village slipping into the sea.^[45][46]

The village of Sandsend, so called because that is where the sandy stretch of beach northwards from Whitby ends,^[47] was developed as a village for those employed at the nearby alum works.^[48] The alum shale depths in the cliffs there reached almost 90 feet (27 m), and the coastal location was able to take advantage of sea transport. Inland locations were hampered by their lack of transport methods, whereas the coastal locations had easy access to the sea.^[39] Additionally, inland locations had the problem of overburden, which in the instances of coastal alum workings, the overburden was simply tipped into the sea.^[15] A lot of the inland locations, particularly the early ones around Guisborough, exported their alum through the Port of Whitby, which not only increased trade through Whitby, but led to growth of the town.^[49]

The alum trade died-off largely as a result of aniline dyes (derived from coal-tar), which were introduced in 1856, being cheaper and less labour intensive to exploit.^[50] Whilst alum workings ceased operating in the second half of the 19th century, commercial exploitation of alum continued in the Sandsend area for a type of cement until well into the 20th century. The product was known as Mulgrave Cement, and was made at a plant in East Row (Sandsend) between 1811 and 1936.^[51][52] The cement was widely used locally for vases, tiles, pipes, chimney pots and concrete blocks.^[53] Some of the old alum sites have gained listed protection, whereas others, such as those at Saltwick Bay, have seen erosion destroy the old alum house on the beach, and coastal erosion threatens the entire site.^[54]