User:The joy of all things/subpage 28

The alum industry in North Yorkshire was a major chemical industry in North Yorkshire England between the 17th and the 19th centuries. The production of alum was suited to North Yorkshire due to the presence of the shale rock needed to make the alum sulphate which was essential as a dyeing agent until synthetic dyes became widely available in the 19th century. Production of alum in North Yorkshire peaked in 1769 with approximately 6,000 tonne produced. The alum industry in North Yorkshire has been labelled the first of the dirty industries in the area, with ironstone mining, steelmaking and the broader Teesside chemical industry all following on from the alum workings. Apart from one large site in Lancashire, almost all of the industrial alum supplied to Britain originated in North Yorkshire. Smaller concerns were operated sporadically in Dorset and London.

History
For over 250 years, the coastal and moorland areas of North Yorkshire were the centre of the alum industry in England. Alum was required for tanning, medicines, and most importantly, as a mordant for fixing dye into clothes, before the industrial revolution allowed dyes distilled from coal via a sulphuric acid method to be readily available. In the Elizabethan age, most alum was acquired from workings in Italy, and as the both Henry VII and Elizabeth I had seceded from Catholicism to form the Church of England, and Italy was staunchly Catholic, the availability of supply was controlled entirely by the Italians and meant that the supply could be turned off due to political whims. 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. 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.

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. 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.

Alum shales were quarried, then burnt on huge open fires of brushwood, sometimes for up to nine months. The stacks for burning often were 30 m wide, and 15 m high. 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 tonne of alum shale rock to produce 1 tonne of alum. The key to the best time to stop heating the resultant liquor was to float a hen's egg in the liquor to act as a hydrometer. When the egg floated to the top of the liquor, it was ready to be separated out. At this point, the yellow iron silicate (known as Slam) was siphoned off the liquor, and could be sold on to make fertiliser. This process of firing, cooling, settling, heating, separating and mixing, has led to it being labelled the first of Yorkshire's dirty industries.

The alum industry helped develop the port of Whitby as not only was the finished product exported through the port, but coal had to be brought in for the process. 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 tonne of urine was needed to make 1 tonne of alum). 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. This had a secondary benefit in sewage disposal for the City of London, and those supplying the urine were paid for the product. Alternatively, burnt kelp was used to precipitate potassium sulphate in the process.

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. In 1769, production of alum peaked at 6,000 tonne, however, by the end of the 18th century, the alum was selling £13 per tonne, when it cost £14 per tonne to make. The band of alum shale in North Yorkshire is typically 100 ft 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.

The village of Sandsend, so called because that is where the sandy stretch of beach northwards from Whitby literally ends, was developed as a village for those employed at the nearby alum works. The alum shale depths in the cliffs there reached almost 90 ft, 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. Additionally, inland locations had the problem of overburden, which in the instances of coastal alum workings, the overburden was simply tipped into the sea. 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.

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. 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. The cement was widely used locally for vases, tiles, pipes, chimney pots and concrete blocks. 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.

Sites
Below is a list of major sites in North Yorkshire providing alum to Britain between 1600 and 1870. The bulk of alum production in Britain on an industrial scale was centred on the North Yorkshire region, although one major site did operate in Lancashire, and others were on the south coast of England, notably in Dorset and Hampshire. Archaeological investigations have determined 22 major sites in North Yorkshire, although 50 have been known to have operated throughout England between the 17th and 19th centuries. Some sites, such as Hawsker Bottoms, were developed but actually produced little, or no alum.

Sites which trialled producing alum, or had a very short working life, included Cringle Moor, Easington, Eskdaleside (17th century works), Hawsker, Ingleby, Kirkleatham, and Thimbleby.