Peter Appleton of the Skelton History Group has generously written the following article on the alum industry of north-east Yorkshire for our project. Peter is also planning to publish a book on the subject in 2018 and organise walks to some of the sites, which I will share here nearer to the time.
As well as the ironstone mining activity that is being documented by this project, there was an earlier industry in the project area: the alum industry. This article sets out to provide some background information about this industry by explaining what alum was, why it was important, how it was manufactured, and when.
What was alum?
Alum was, and is, a colourless crystal; a double sulphate of aluminium and one other element, most commonly either potassium or ammonium. The chemical formulae are:
- Potassium alum – 2KAl(SO4)2
- Ammonium alum – 2NH4Al(SO4)2
Why was it important?
The economy of England, prior to the Industrial Revolution, centred around wool and linen. This was very much a legacy of the monasteries. They had established the rearing of sheep, in very large numbers, from which to produce the wool, and the cultivation of flax, from which to produce the linen. The middle and upper classes of those days liked to wear bright, rich colours. The only dyes available at that time were derived from plants and minerals. These were not colour fast during washing. To fix these natural dyes to the natural fibres of the wool and linen cloth, it was necessary to soak the cloth in a mordant before putting it through the dye bath. That mordant was alum.
Until the reign of Henry VIII, alum had been sourced from Italy. The industry and trade in alum, at that time, was tightly controlled by the Pope. When Henry VIII fell out with the Pope, over the matter of his divorce from Catherine of Aragon, it became imperative to find a source of alum within his realm. After some fifty years of prospecting and experimenting, a viable process was arrived at for manufacturing alum from a rock stratum that was particularly abundant in north-east Yorkshire.
“Alum works, Robin Hoods Bay” by H.B.Carter (1843)
How was it manufactured?
The short answer to that question is: slowly. The slightly longer answer is: very slowly! From first quarrying the alum shale, to shipping the first cargo of alum crystal, could take twelve months or more. The first part of the production process took place outdoors in a quarry. Here men would use pickaxes to excavate the rock from the quarry face, and then use mauls to break the pieces down to a more usable size. Shovels would be used to load the broken rock into wooden wheel-barrows, in which it was transported along wooden planks, later iron plates, to the burning place. Here the rock would be calcined in heaps known as clamps.
The clamps were created by laying down a base of brushwood, 15-20 feet across and 3-4 feet high. Around and on top of this, the rock was added until the pile was 6-8 feet high. At this point the brushwood was lit and the burning started. More rock was added to the heap and around its sides, until the clamp was perhaps 200 feet in diameter and 60-90 feet high. The clamp was then left to burn, in a controlled manner. The skilled eye of the heap controller would gauge when the burn had progressed to a suitable state.
At that point, the burnt rock, now called “mine” by the alum workers, was removed and placed in an empty steeping pit. Spring water and collected rainwater would be used to leach the soluble salts out of the mine, resulting a solution called the liquor. The steeping process was a complicated affair, involving pumping of the liquor from one pit to another in a carefully regulated sequence. Eventually, the liquor arrived at the strength desired. It was then pumped into a holding cistern, to await being sent to the alum house. When it was required at the alum house, it would be transported there along wooden troughs or stone conduits.
On arrival at the alum house, the liquor was run into cisterns and left to stand overnight. This allowed debris and detritus to fall to the bottom or float on the surface. Either way, the clarified liquor could now be used in the alum house. It would first be run into large evaporating pans set over open coal-fired furnaces. The pans were made of lead and were around 11-12 feet long, 5-6 feet wide and 2-3 feet deep. They were set on iron plates which, in turn, were set on iron bars, with the coal fires below them. The liquor was brought to the boil and kept there until the desired strength was arrived at.
When it arrived at the appropriate strength, the liquor was run off into settlers where an alkali was added. The effect of the alkali was two-fold. Firstly, it brought about reactions whereby unwanted chemicals were precipitated out. Secondly, it reduced the acidity to the point at which the alum crystals could form. Once the waste products had precipitated, the liquor was run off into coolers; large wooden casks with numerous wooden frames suspended in them. Here the alum crystals had numerous surfaces on which they could form and grow.
The crystals would then be scraped off the frames and the sides of the coolers and washed with fresh spring water, to remove any surface impurities. Then they would be transferred to a roaching pan, smaller than the evaporating pans but made of lead just the same. Here, just enough hot water would be added to dissolve the crystals. The liquor, after a final check on its strength, was transferred to the roaching casks. Here it would cool for about 10 days. The outer cask would then be dismantled, revealing a column of solid alum crystal. This would be left for another 10-15 days to allow the liquor within the column to have a chance to crystalize still further. At the end of that period, the column would be broken into and the saleable alum would be bagged ready for transport.
“The Costume of Yorkshire” by George Walker (1814)
When did all this take place?
The earliest prospecting for alum, during the very end of Henry VIII’s reign, took place in Ireland, around Wexford. During the reign of Elizabeth I, further prospecting occurred on Lambay Island, off the Irish east coast. In England, the earliest attempts to make alum took place on the Isle of Wight and in Hampshire. About 1600, or shortly thereafter, attempts were made at Bellman Bank, Guisborough, and at Springbank, also known as Slapewath. A little later, works were started at Selby Hagg, Skelton and at Sandsend.
These early works consistently struggled to make alum. There was no chemical knowledge to turn to. Everything was done by trial and error – with a predominance of errors! It was, after all, the era of alchemy rather than chemistry. Vast sums of money, from both private fortunes and the Treasury’s coffers, were spent in trying to perfect the process. And vast is the only suitable word to use. Something like £150,000 pounds or more had been expended between 1550 and 1630. At least half a dozen individuals had been bankrupted; and those pounds were Elizabethan and Stuart pounds. Convert them to today’s values, and we’re talking several tens of millions of pounds.
From 1630 onwards, alum works sprang up all around the northern escarpment of the North York Moors and along the coastal cliffs from Loftus to Ravenscar. Competitor works came into being at Pleasington, Lancashire, at Hurlet and Campsie in Scotland, and at Neath in south Wales. Finally, in the mid-19th century, an industrial process for making alum was patented by Peter Spence. His works at Pendleton, Lancashire and Goole, Yorkshire were each capable of producing more alum in one month than the entire Yorkshire alum shale works ever produced in a year. By 1871 the last two alum works in north-east Yorkshire had ceased operation, driven out of business by more efficient production processes and the arrival on the market of synthetic dyes that did not require a mordant to make the colour fast.
1 – Thimbleby
2 – Carlton Bank
3 – Kirby Bank
4 – Ayton Bank
5 – Belman Bank
6 – Newgate Bank
7 – Spring Bank
8 – Selby Hagg
9 – Saltburn (the alum house for Selby Hagg)
10 – Loftus
11 – Boulby
12 – Kettleness
13 – Sandsend
14 – Saltwick
15 – Hawsker
16 – Stoup Brow (or Stow Brow)
17 – Peak
18 – Littlebeck
19 – Godeland Bank
20 – Eskdaleside
21 – Asholme
22 – Rockhole
23 – Holmes
24 – Grosmont
Alum house – the collection of buildings in which the liquor from the steeping pits was processed through to the finished product, the alum crystals
Alum works – the quarry and all its associated fittings such as bared rock, a burning place, steeping pits and storage cisterns
Erected – The setting up of a new alum works and alum house, including the preparation a quarry, a burning floor, steeping pits, and alum house complex and the necessary supplies of water.
Laid down – The cessation of production but with the capability for it to be quickly restarted (today we might use the word mothballed to convey a similar meaning)
Mine – Not a place where mineral ores are extracted from underground, as is the modern usage, but the alum shale itself, especially after it had been quarried and burnt
Mordant – A substance which, if applied to material before it goes into the dye bath, will help the dye pigment bond more strongly with the fibres of the material. This produces a richer, brighter result that is colour-fast when washed
The following published sources are the ones most likely to be available in the collections of the reference libraries:
Miller, I (ed.), Steeped in History; North York Moors National Park Authority, 2002
Pickles, Roger L., “A Brief History of the Alum Industry in North Yorkshire 1600-1875”; in The Cleveland Industrial Archaeologist Issue no.2, 1975
Quinn, K., “Boulby Alum: The Works Diary of George Dodds 1772-1788”; Cleveland Industrial Archaeology Society, 2009
Turton, Robert Bell, “The Alum Farm”; Whitby: Horne & Sons, 1938
Young, George, “A History of Whitby and Streoneshalh Abbey”; Whitby: Clark & Medd, 1817
The network of county archives holds a vast collection of original documents created by or about the alum industry. The largest holdings are to be found at:
North Yorkshire County Record Office, Northallerton
Palace Green Library, Durham
the private archives of the Marquess of Normaby, held at Mulgrave Castle, Lythe
Northumberland Archives, Woodhorn Museum