This is a guest post by Brian Kaller, who blogs at Restoring Mayberry.
Explore the now-ruined estates of the Irish countryside and you
occasionally find a stone cylinder, as much as several metres high and
wide, open at the top and with a small door at the base.
Some resemble the medieval fortresses that still dot the landscape
here -- but no one built fortresses so tiny, or half-buried in the side
of a hill.
In fact, they are kilns for lime burning, a
now-forgotten industry that sustained many agrarian communities before
energy became cheap.
“Lime” here means neither the citrus fruit nor the tree, but refers to a white
powder derived from limestone. For at least 7,000 years humans created
lime in kilns, as they might have hardened pottery or smelted ore, and
used the material for dozens of purposes now largely replaced by
fossil-fuel by-products – perhaps most commonly to create mortar for
construction.
British and Irish farmers, though, found it most important to neutralise
acid soils and multiply crop production – as much as fourfold, by some
contemporary accounts. For hundreds of years until the mid-20th
century, lime supported a vast and vital network of village industry --
quarries to mine the limestone, carts and barges to transport it, and
specialists to monitor the burning. In the late 1700s, according to one
survey, County Cork alone was said to contain an amazing 23,000 kilns,
or one every 80 acres. (1)
Limestone is mainly coral and shells of long-extinct sea creatures,
squeezed over aeons into a solid mass of calcium carbonate, or CaCO3.
When burned at 900 degrees C or more it vents carbon dioxide (CO2),
leaving behind the volatile calcium oxide (CaO) – “quicklime,” “burnt
lime” or “unslaked lime.” Then, when combined with water – hydrated or
“slaked” -- the quicklime became calcium hydroxide or Ca(OH)2, and could
be put to many uses. Confusingly, all of these have been called “lime”
at times, but in this article, we will call the original rock
“limestone,” the caustic material from the kiln “quicklime,” and the
hydrated final product “lime” for clarity.
Roman Concrete
The earliest use of lime dates to present-day Turkey between 7,000
and 14,000 years ago, and many ancient civilisations used it to create
mortar between stones. The Romans, however, took lime a step further,
mixing it with various other ingredients to create an early version of
cement. In fact, their version has proven superior to our own in some
ways. Our concrete lasts only decades – as little as a single decade in
seawater -- while Romans created concrete that not only formed in
seawater, but have withstood the pounding of waves for 2,000 years.
Picture: Disused lime kiln above Murlough Bay, Ireland, by Minipixel.
The secret, according to two papers released in the summer of 2013, involved mixing quicklime with volcanic ash
to form mortar. Volcanic ash was plentifully gathered from the volcano
at Vesuvius, according to Pliny the Elder – ironically, the same volcano
that would later kill him. Romans then packed this mortar into wooden
forms and lowered them into seawater, which caused the quicklime to
react and form a lime-and-ash mix of waterproof cement.
The papers’ authors say such techniques could prove useful even today;
not only did their concretes stand up to time and the elements better
than ours, but such methods are “greener” – generating less carbon
emission – than our cement manufacture. Crushing rocks into Portland
cement powder requires enormous quantities of energy and accounts for
seven per cent of all industrial carbon emissions on the planet. (2) (3)
(4) (5) (6)
Picture: One of the forty lime kilns built between Skipton and Bradford along
the Leeds-Liverpool Canal, Bradford's demand for lime being one of the
key reasons the canal was built. Photo credit: Peter Hughes.
Romans brought such technologies with them as they spread across
Europe, so lime kilns appeared in Britain with their invasion and
disappeared for several hundred years after they left. In Ireland, where
Romans never set foot, Normans apparently brought the technology in the
1200s, to build the round towers that still frequently stand today. (7)
Whitewash, Limelight and other applications
Lime also forms the basis of whitewash, used for centuries to protect
and brighten structures, fences, vehicles and even trees, without the
alarming and unpronounceable stew of toxic ingredients in many modern
paints. Whitewash is fundamentally a mix of lime and water, although it
could also contain salt, milk, linseed oil for water-proofing, or hair
or cereal husks for strength.
The dried lime was safe to handle and even for animals to lick, but
remained mildly alkaline enough to disinfect barn and dairy walls. Its
brilliant whiteness was valued in places like Britain and Ireland, where
the winters grow very dark – Irish cottages were traditionally
whitewashed in spring and again before Christmas. In sunnier climates,
however, that same colour helped keep buildings cool.
Lindisfarne had a large limeburning industry and the kilns, which were
built in 1860, are among the most complex in Northumberland. Picture by Tom Blackwell.
Lime had many other uses: Farmers rubbed it on their livestock’s feet
as an antiseptic, or painted it onto fruit trees to prevent fungal
diseases. Some mixed a bit of lime into well-water to disinfect it, or
to preserve eggs for months without spoiling. Tanners used it to remove
hair from hides, gardeners to repel slugs and snails, printers to bleach
paper.
Even the corrosive quicklime, the calcium oxide that came straight
from the kiln, had many uses before it was hydrated. It kept pantries
and store-rooms dry – the 1915 household manual “The Best Way”
recommended keeping a bowl of it to reduce humidity, as it sucked
moisture from the air. It caught fire easily – sometimes too easily –
and was used to make an early, high-intensity lamp for the stage – the
original limelight. (8)
Terrorist Weapon
It also made a rather fearsome weapon, as it could sear the skin and blind the eyes. In David Hume’s A History of England,
he recounts a battle between English and French ships around 1216, in
which the English captain Phillip d’Albiney ingeniously used quicklime
to turn the tide of battle. He saw that the winds were blowing from his
ships to French fleet, and “having gained the wind of the French, he
came down upon them with violence; and throwing in their faces a great
quantity of quick lime, which he purposely carried on board, he so
blinded them, that they were disabled from defending themselves.”
Lime kiln in Prague. Picture by Radim Stezka.
The compound made a handy terrorist weapon as well; when Irish
reformer Charles Parnell spoke at a political rally in 1891, someone in
the crowd threw quicklime at his face, and “had not [he] shut his eyes
in time, he would undoubtedly have been blinded,” his wife Katherine
later wrote.
Quicklime was also shovelled into graves to decompose bodies more
quickly, as Oscar Wilde saw when he was a prisoner at Reading Gaol
(Jail) in Britain:
And all the while the burning lime
Eats flesh and bone away
It eats the brittle bone by night
And the soft flesh by the day
It eats the flesh and bone by turns
But eats the heart away.
Eats flesh and bone away
It eats the brittle bone by night
And the soft flesh by the day
It eats the flesh and bone by turns
But eats the heart away.
Lime in Agriculture: Sweetening the Soil
Its use in agriculture, however, eclipsed any other use on these
islands, so valuable was its ability to turn acid bog-lands into
croplands. Some 40 per cent of the arable land in the world is too
acidic for many plants to grow – the more acidic the soil, the more
toxic aluminium plants absorb. These days, farmers often treat such
soils with crushed limestone or other energy-intensive products, and
scientists like Chris Gustafson of the University of Missouri are trying
to genetically engineer aluminium-resistant crops. In earlier eras,
however, farmers found that lime temporarily “sweetened” or neutralised
the soil. (9)
This made lime so valuable that many
agrarian communities supported a network of local industries to create
it -- quarries to mine the limestone, wagons to transport the rocks by
road or barges by canal, and specialists to supervise the burning. By
the mid-1600s many families in County Cork, Ireland, for example, paid
their rent by lime-burning on the side, according to a civil survey of
the time. (10)
Farmers treated the soil in quite a straightforward manner: they
shovelled quicklime straight from the kiln onto a horse-drawn cart,
drove the cart to the needed field and drove the horse back and forth
across it as though ploughing. Every several metres the farmer stopped
the cart and scooped several shovels of quicklime in “falls” on the
ground -- six to eight barrels to the acre.
Spreading a highly caustic compound onto cropland might sound
inadvisable, but the next rain both hydrated it into lime and soaked it
into the ground. Transporting the quicklime, however, was dangerous
work, as it could spontaneously burst into flame and burn carts and
barns, or simply to eat through wooden containers if it wasn’t spread
quickly. (11) (12)
The process only sweetened the land for a limited amount of time,
according to contemporary reports – three years in some fields, twelve
years in others, depending on conditions. In any case liming had to be
continually re-applied or it “enriched the father but impoverished the
son,” went the saying, so the kilns were kept in steady business. (13)
Operating the Kiln
Kilns
themselves needed to be carefully situated: they needed to be as close
as possible to quarries, so that hundreds of tonnes of rock could be
carried with as little effort as possible, by horse or barge. At the
same time they had to lie as close to the lime’s destination as possible
– a fortress or church being built with mortar, or fields that needed
sweetening -- so that the quicklime could also be transported without
incident. Moreover, they could not be situated near populated areas or
even campsites, as the burning lime gave off noxious and potentially
lethal gases.
The canal wharf built at the base of lime kilns constructed in 1842, Dudley, England. Picture: Paul Englefield.
The brick or stone structures were often built into hillsides to
allow people to easily transport coal and lime to the open top, or
mouth, and were often several metres across and about as high. On the
inside they usually tapered down so that gravity alone fed the fuel
down, and at the narrow bottom of the cone, one wall had an arched
opening or “eye.”
The kiln had to be filled carefully, with precisely measured
amounts and materials – if the lime did not bake at a high enough
temperature for long enough, the stone would not transform into
quicklime and the work would be in vain. Lime-burners filled the bottom
of the kiln with the driest wood possible – furze-wood was often
mentioned – and then the men lay alternating layers of fuel and
limestone.
Perhaps the most common fuel was “colm” – anthracite coal – although charcoal could also be used, as well as “turf”
– dried peat from the bogs here. Whatever the fuel, it had to be in an
opaque layer, insulating the chunks of limestone from the sides of the
kiln and from each other, according to old lime-burners interviewed
decades later for Irish national radio.
Sleeping by the Kiln
Once the kiln was filled, the wood – at the bottom of the kiln, by
that little door – was set on fire, and that, in turn, lit the fuel
through the rest of the structure. Once the kiln was lit there was no
going back; the lime-burners had to maintain a watch over the kiln for
the next three or four days, sleeping nearby. Burning was often done in
winter, when there were fewer farm chores to be done, so it must have
been tempting for men sleeping out in the cold to move closer to the
warm glow of the kiln. According to lime expert Colin Richards, however,
sleeping by the kiln was extremely dangerous, between the poison gases
and the open pit. There were cases of itinerants sleeping near the mouth
for warmth, he said, rolling into it as they slept and being roasted
alive.
Lime kiln in Quijorna, Spain. Picture by Álvaro Moreno Gómez.
Certainly
the men did exhausting work for days at a stretch, making them “thirsty
as a lime-burner” as the saying went. A single kiln could hold a
hundred tonnes of material, which had to be shovelled in by hand, yet
delicately measured and arranged inside. Of course there was less to
shovel out – the coal had burned away, and the limestone had lost some
of its mass – but that material was much more difficult to handle.
“Drawing out the lime underneath was the dirtiest part of it,” said
one anonymous lime-burner who worked in Ireland in the 1930s and 40s and
was interviewed for a radio documentary in 1981. “It was there that you
got the dust, and you got too much of it and you began bleeding from
the nostrils.”
Magic and Ritual
With their furnace-like heat, poison vapours, alchemical
transformations, hazardous products and vital importance to agrarian
survival, it was perhaps inevitable that farmers associated kilns with
all kinds of magic and ritual. According to Irish elders interviewed in
the 1930s, young people often performed Halloween rituals around
lime-kilns to find out who they would marry.
In one instance, fairies were said to have killed off a farmer’s
livestock after he inadvertently built a kiln in their way. Other
peoples were said to have summoned evil spirits there; a reverend in
Carnmoney, rumoured to have sold his soul to the Devil, was said to have
courteously invited him to a kiln so the Devil would feel at home.
(15)(16)(17) The lime burners themselves had a simpler ritual, one they
said was practiced among “all the lime burners of old.”
“You took a bottle with you that morning … of holy water,” one said,
and before the kiln was fired up “you just sprinkled it on top the
stones, and made the Sign of the Cross, for you were burning – what they
used to say was -- you were burning the bones of the Earth.”
Written by Brian Kaller----------------------------------------------------------------------------------------------------------------------------------------------
Notes: (1) Topographical Directory of County Down, by Samuel Lewis, 1837.
(2) “Microscopy of historic mortars — a review,” by J. Elsen, Cement and Concrete Research, July 2005
(3) “Chemistry and Technology of Lime and Limestone,” J. Elsen, Cement and Concrete Research, December 2005
(4) “Material and elastic properties of Al-tobermorite in ancient Roman seawater concrete,” by Marie D. Jackson, Juhyuk Moon, Emanuele Gotti, Rae Taylor, Abdul-Hamid Emwas, Cagla Meral, Peter Guttmann, Pierre Levitz, Hans-Rudolf Wenk, and Paulo J. M. Monteiro, Journal of the American Ceramic Society.
(5) “Unlocking the secrets of Al-tobermorite in Roman seawater concrete,” by Marie D. Jackson, Sejung Rosie Chae, Sean R. Mulcahy, Cagla Meral, Rae Taylor, Penghui Li, Abdul-Hamid Emwas, Juhyuk Moon, Seyoon Yoon, Gabriele Vola, Hans-Rudolf Wenk, and Paulo J. M. Monteiro, American Mineralogist.
(6) “Roman Seawater Concrete Holds the Secret to Cutting Carbon Emissions,” Berkeley, http://newscenter.lbl.gov/news-releases/2013/06/04/roman-concrete/
(7) “Pre-industrial Lime Kilns,” English Heritage, May 2011
(8) The Best Way - A Book Of Household Hints & Recipes, 1915
(9) “Famine Fighter,” Illumination magazine, Spring / Summer 2013
(10) The Ancient and Present State of the County and City of Cork, by C. Smith, 1815 edition.
(11) “Burning the Bones of the Earth,” a documentary by Radio Telefis Eireann, 1981
(12) Edwardian Farm, BBC Television
(13) Essay on the Use of Lime as a Manure, by M. Puvis, 1836.
(14) “Pre-industrial Lime Kilns,” English Heritage, May 2011.
(15) Maureen Cunney, Currower, Attymass, Ballina, County Mayo, as part of the 1937-38 schools initiative.
(16) Researches in the South of Ireland, by Thomas Crofton Croker, p. 82
(17) Irish Witchcraft and Demonology, by St. John D. Seymour, [1913]
