Issue 4, 18th December 1995: Thomas Challoner, Alum Alumnus
By Adam Hart-Davis.
Computing, Law, SciFi, Sport(13th).
This story of the Peak Alum Works at Ravenscar is incredible, but true.
Ravenscar, a beautiful desolate stretch of North Yorkshire coast, where steep cliffs look out over the bleak North Sea, does not look much like an industrial wasteland, but in fact it was the birthplace of the British Chemical Industry---a great international business that involved Henry VIII, tonnes of seaweed, and vast quantities of stale human urine.
The problem was the Tudors and Stuarts weren't much good at dyeing.
The value of woollen cloth in those days depended on how well it was dyed. The difficulty was this. When they wanted to dye some wool with vegetable dye, the dye wouldn't stick on the wool. You can try it yourself; boil up some onion skins and extract the lovely yellow dye. Dip in a white wool sock, and although it comes out yellow, the moment you rinse it in cold water all the dye comes out again.
The Romans had discovered a trick. They got hold of some alum, which they found lying about in the ground in Italy, dissolved it in water, and dipped their socks in the alum solution first. Try that with your sock; it goes yellow, and it stays yellow, because the aluminium in the alum acts as a mordant---that is, it's like a set of teeth; it sticks to the dye and bites into the wool fibres.
So alum was vital when they wanted to dye cloth, and the Romans also used it for softening leather, fireproofing their uniforms, making smooth paper, and probably for stopping the bleeding when they cut themselves shaving. Alum still has plenty of uses today.
In the fifteenth century the whole alum industry came under the control of the Vatican. This meant that when King Henry VIII had a row with the Pope because he wanted to divorce Catherine of Aragon, the supplies of alum to England were cut off, and the clothing industry took a nose-dive. The only way to get things dyed was to send them to Flanders---that is Belgium---where the alum was inferior and expensive.
So when Thomas Challoner set up an alum industry in North Yorkshire in the early 1600s, it was definitely good news---in fact such good news that James I gave him a monopoly on the industry.
There are two really impressive things about the alum industry: the incredibly complex manufacturing process they developed at Ravenscar---and other places on the east coast---and the sheer scale of the operation.
The trouble was that unlike the Romans, the industrial chemists of Ravenscar couldn't just mine alum---they had to make it. First they took some rock---and they certainly took a lot of rock. The two huge quarries at Ravenscar must have yielded more than a million tons.
Just imagine what this meant; in a remote rural area, the industry employed hundreds of people through the seventeenth and eighteenth centuries. All summer, the pickmen hacked lumps of grey shale from the cliff with pickaxes. Barrowmen wheeled it down perilously steep and narrow paths to the bottom, and built huge bonfires called clamps, 10 or 20 metres high. They put brushwood at the bottom to start the fire, and then piled shale on top.
The fires smouldered away for nine months---yes, nine months---and the rain on the outside kept them from getting too hot. After several months in the fire, the whole rock turned red.
Then the liquormen tipped the red rock into big pits of water to extract aluminium sulphate. The used red rock was hauled out of the pits by the pitmen, and tipped out to make great spoil heaps---which are still there, covered with yellow-flowered, prickly gorse.
Meanwhile the aluminium sulphate solution was channelled into stone gutters, and ran 300 metres down the hill to the alum works on the top of the cliff, collected in a tank, and when each batch was ready it was run down into the treatment works, boiled, and allowed to settle.
Now, a modern-day chemist might explain that the exact chemical they wanted to use as a mordant was potassium ammonium alum---that is:
K SO Al (SO ) .24H O/(NH ) SO Al (SO ) .24H O 2 4 2 4 3 2 4 2 4 2 4 3 2because this was the best source of soluble aluminium. To make it they needed aluminium sulphate, which they had made, plus potassium and ammonia. They got their potassium by toasting sea-weed! Specifically they shipped in kelp from far and wide---some of it came from the Orkneys, several hundred miles north.
Next they needed ammonia, and for that they used, believe it or not, stale human urine. One adult produces perhaps a litre and a half of urine every day. To begin with they collected it locally; there were barrels outside every farmhouse in the area, and all the workers were invited to contribute. But the industry prospered, and the demand outgrew the supply.
In the heyday of the industry they used about 200 tonnes a year, which would have meant the urine from about a thousand people. There simply weren't enough locals, and so they shipped the urine in from Newcastle and from London. Buckets stood on street corners, and men with barrels came around once a week to collect it. The barrels were shipped up here in lye boats. Imagine what it must have been like unloading barrels of very old urine on to the rocky shore in an easterly gale!
The smell must have been quite something! As it gets older, urine becomes richer in ammonia because of biochemical decomposition of the urea.
It was well known in the trade that the urine from Poor working people was much better than the urine from the wealthy, because they did not Partake of so much strong drink!
Both the toasted seaweed and the stale urine were unloaded on the rocks and then winched up the steep cliff on a rack railway to the factory on top, where the new ingredients were added to the brew. Finally, after the urine and seaweed had been added to the aluminium sulphate liquor, they let it stand, and alum crystals settled out of it.
For 250 years this was how the basic mordant was made to dye English wool.
About 1855 someone invented a way of making alum synthetically, and at about the same time aniline dyes were invented. They came from by-products of town gas works, and didn't need alum, because they contained their own mordant dyes. So after 250 years, the alum industry died.
What really amazes me is that they worked out how to do all these complicated reactions in the first place. It's relatively easy for us to understand now because we can use chemical formulae and a lot of hindsight. But they must have discovered by trial and error. Picture the scene in the lab as young Thomas gave instructions to his research team:
``Excuse me Mr Challoner, I've found some grey rock. What do you want me to do
``I don't know. Try burning it for nine months, and see what happens.''
``I did that, Mr Challoner. It's gone red.''
``Oh good! Now see what happens if you mix it with toasted seaweed and soak it in stale human urine...''
This seems extremely unlikely. But they did discover how to make alum at the Peak Works at Ravenscar, and the first British chemical industry was set up, something like 150 years before chemistry was invented.
As for Thomas Challoner, he was unlucky, for he grew old before the industry was really established. But he always had confidence in the future, and he instructed his servants to collect his urine, and sell it for a penny a firkin!