Text and photographs: Law Siak Hong
Lime is an essential building material. To learn more about it, a team of conservationists from Penang’s George Town World Heritage Inc. came to ‘Pulai-Ipoh’, a major centre of lime production (and limestone paving). Who would have thought that we had to commiserate about the sad exit of a traditional trade?
The visitors had travelled in the morning light and arrived in Ipoh for breakfast. To slip into the mood, we decided on a quick look at some old shophouses in Kampong Kepayang (read our last blog), five minutes away, where lime was used extensively in their construction before the days of modern-day cement. We could have spent more time romancing the ruins but the day’s programme beckoned.
In the meeting room of a plant in Keramat Pulai, our guru Harrison gave us an education on lime.
Harrison is well respected in the industry. Over the course of an hour, we learnt from him why the conventional kiln produces superior quicklime, and that quality loses out to the lesser and cheaper products from the contemporary tower kiln. We learnt, too, that lime is critically important in our daily lives. It is used in myriad ways: water treatment (to ‘soften’ water), sugar refining, food and food by-products, toothpaste, detergents, cosmetics, chemical manufacture, paper, ceramics, construction, smelting, steel, road, petroleum, agriculture and more. Is it for these products that we are destroying the biodiversity and natural beauty of our irreplaceable limestone hills? There must be a way out. Let’s reduce our reliance on them, for starters, and put a moratorium on new hills which have not yet been exploited.
GTWHI team: three architects and a videographer: Yee Li, Yeow Wooi, Que Lin and Gwynn, with our guru, Harrison (middle). Missing here, the researcher Muhammad Hijas appears in another photograph below.
Post-theory, we left the classroom for site visits. The sun was mild. We drove past limestone hills and came to the conventional lime kilns near a small limestone outcrop in Bercham, Ipoh. We discovered that these last conventional lime kilns in the Kinta Valley had been abandoned quite recently. (Why did I not ‘recce’ ahead of the visit?) In the work shed, a couple of workers were bagging the last scraps of quicklime. According to them, there is no more supply of rubber wood for the best fire to ‘cook the rocks’.
Feeling and testing the quality of the lime.
A file picture of the kiln when it was in operation; note the stack of rubber wood. GTWHI’s urban planner/researcher, Muhammad Hijas, squeezes into the lime kiln for the medieval feel of the ‘room’.
Set 80 metres apart, two rows of kilns, three in each, face each other across a little creek – a fire barrier, perhaps. About 4 metres in diameter and 5 metres high, the cylindrical kilns rise behind a retaining wall: a concrete and brick structure. Entry into the kiln to stack the rocks is through a narrow, man-sized passage. In front of the retaining wall is a long shed, a roofed work space with a storage room at one end and at the other, living quarters for the workers, who keep a 24-hour watch on the fire for three days. Work is also done on an upper level. Compacted earth, levelled with the
File picture: limestone piled around on the upper level, to be cooked in the kiln and become quicklime.
rims of the kiln openings, provides the space where rocks would wait to be dropped into the kiln and stacked into a domed vault, piece by piece. What skills, what occupational hazard! The back of the kilns slopes away gently for a small truck to bring up the rocks.
The abandoned kilns and the cool isolated setting. Note the limestone hill in the background. Workers’ quarters on the right have been reconfigured into a store. What’s in store for these kilns?
Harrison walking past the retaining wall of the abandoned kiln.
One set of kilns was already partially concealed by bushes, creepers and wild grass. Dead branches had been dumped into the hollow.
Yeow Wooi recording the structure of the retaining wall at the passage (left). Piqued by the construction, Que Lin the videographer switches role and poses at the passage (right).
While we were looking around, someone unlocked the steel door to the only kiln which had remained intact and accessible! The passage was partially sealed with bricks, and we had to bend down low or crawl in. It felt like we had stepped back in time, into a circular medieval room under an open sky; we would be right at home draped in hessian, mud and ash. White lime had caked up on the bricks lining the kiln, while green moss had found their footing on the wall and the floor.
File pictures: Looking down into the kiln and the narrow passage. The bricks lining the kiln are laid on their edges. Note the irregular surface of the wall.
After lunch and iced tea, we went to a tower lime kiln south of Gopeng. A surprise was waiting in the wings. As we took the first bend of the dirt road to the plant, a brick wall came into view. Hugging the foot of the limestone cliffs were twelve, or more, conventional kilns in the wild. A poignant moment: nature had reasserted its mastery over man-made objects.
Effective and responsible action: thin out the vegetation selectively (aesthetically) and manage the ground covering and the trees; then maintain a clear path to the upper level of the kilns and mark it with a guide rope. Would the holes and the wild vegetation pose any threat to the visitors?
Later, at the plant, we were told that the lime company might adopt and maintain this evocative historical site, for corporate responsibility purposes. For sustainability, cost effective measures are practical and appropriate. Less is more. Perhaps the management will consult with us: PHS.
While a conventional kiln is seen as a hole in the ground, the tower kiln pierces the air. For industrial security, no photography was allowed. The tower kiln is a tall, heavily insulated steel drum, tapered and stumped at both ends. It is suspended from huge I-beams, supported by a massive concrete base. Around the kiln, an open steel staircase links several platforms, where various operational procedures and tasks can be performed. On a tilt, the bucket elevator raises its load of limestone up to the top to tip the rocks into the kiln. Progressing downwards (!), the rocks are heated, cooked and cooled. Quicklime powder, the finished product, is collected at the base and piped into the adjacent silo. It takes sixteen hours for the tower kiln to make quicklime. In comparison, the conventional kiln takes nearly two weeks.
File pictures of the retired tower kiln, similar to the ones we visited in Gopeng, with twin silos (left). A view from the top at the level of the gangwalk from the kiln to the top of the silo (right).
Our close encounter with the retired but magical tower kiln in Keramat Pulai was scratched due to rain…. Suddenly, I am overwhelmed with a deep sense of loss, of a magnitude I have yet to come to grips with. What can be done to save and reintroduce the technology and the art of the conventional lime kiln which produces superior quicklime for our building craftsmen? In the meantime, we must settle for lime of a poorer quality, but one that is cheaper and much quicker to make. Would there be a demand for the superior product or would it be simply a waste of time? This is the kind of problem conservationists grapple with.
Perak Heritage Society 
My contractor had a phone call from his lime supplier in Ipoh the other day – another contractor was asking if its true that in Penang contractors use lime plaster without cement! Well some do – but sadly not all.
George Town World Heritage Inc promotes lime mortar / plaster for walls and lime concrete for floors, as a simple and authentic way of ensuring the health of heritage buildings. But we don’t just stop there – we want to learn as much as possible about lime and its qualities. Hence our trip to Ipoh and invaluable day spent with Hong & Harrison.
We literally saw the final breath of the quicklime factory as they stitched up the last bag of quicklime taken from the last firing of the kiln.
Currently I am slaking quicklime burnt at the standard commercial temperature – 1,000-1,400 degrees C, but am looking for lime burnt at 800 degrees C which is stickier and better for traditional building works- sadly we were to late this time.
Its incredible to consider how many times a day we use or touch something that has had lime in its process of production. The Lime industry using such kilns as those shown above, were the backbone of this nations development – without it agriculture, fisheries, steel industry let alone the building industry would have struggled to grow. Sad therefore that we don’t have a Museum of Lime to celebrate this incredible material and its history.
SInce the trip and the opportunity to learn so much about the material, I am sadder than ever to have seen the last kiln close. We have spread the news of our findings and are surprised with the support – good lime is needed to look after our heritage… can a kiln or two be saved?
Hi Hong / All
thank you for an informative article.
Much was stressed that conventional kiln lime is superior but little by way of in what aspect other than “being stickier” and for “maintaining health of heritage buildings”. Perhaps other industries that also use lime aren’t too finicky about how it’s produced or its finer qualities, Other than preserving period authenticity, perhaps conventional kiln lime have specific or special properties, albeit limited application, which may warrant a premium price and sustain its availability.
It would be helpful for both supplier and buyer, to recognise the unique qualities of conventional kiln lime such that these may be specified and just as easily verified, much like different grades of OPC or PPC.
Certainly the fuel used in the burning process imparts unique qualities to the lime by way of impurities and reactive byproducts, and these may also be difficult to control in manually operated batched processes like conventional kilns. Be as it may, if these ‘modifiers’ like fuel ash impurities, roasting temperature profile, dwell time, etc can be identified, i’m certain they can just be as easily replicated / introduced in tower kiln processes to produce lime of the desired quality, consistently, and specifically for heritage applications.