Tai Om Kiln
Tymon Mellor: The village of Tai Om sits on the south side of the Lam Tsuen valley at the foot of the Tai Mo Shan escarpment. Like many New Territories villages, it has experienced a building boom with village houses and a recently constructed road opening up the area. However, at the back of the village in an area of derelict buildings, sitting within the long grass sits a former pottery kiln that has recently gained wider attention.
According to local historians, the village was established by the Cheung clan in the 17th century, with farmers initially growing tea on the slopes of Tai Mo Shan, but then moved into the valley to grow corn, rice, and vegetables. In around 1850, the great great great grand father of one of the current villagers, along with his brothers and uncles, constructed the kiln for the manufacture of bricks, roof tiles and pottery. The former items were then used in the building of new homes for the growing clan. The kiln is believed to have closed around 1900 and with the abandonment of the adjacent village houses in the early 1970’s, it is being slowly absorbed back into the landscape.
Below is a sketch, titled 《一九五零大菴燒窰圖》 of what the site may have looked like in the 1950’s based on villagers’ recollection. The village house was called six hakka houses (客家六間屋), and formed by six similar size buildings with a small store on the left side. The buildings had a single common kitchen and bathroom and water was supplied to the property by a water pipe from a little steam of the hillside. The village children would play hide and seek with friends and brothers in and around kiln. The villagers remember that the kiln had no door on the entrance but inside the chamber was divided into several smaller kilns which burned different things.
The kiln is of masonry construction, forming a dome around 4m across and 4m high with a central hole in the roof. The lower portion of the structure is formed from what looks like a cut firebrick, 360mm long by 130mm high on a mortar bed. The surface of the brick is smooth but where the brick is exposed, it looks friable possibly as a result of voiding to reduce heat transfer. As the roof curves, brick construction has been adopted using what looks like locally fired clay bricks.
The structure looks to be typically one brick thick, but there are three and possibly four chambers on the outside associated with ports in the kiln wall. Part of the wall has been lost and now forms an entrance in to the structure. Debris of bricks, pots and soil cover the floor but the original entrance would have been an arch and incorporated the firebox and access.
It is not clear how the kiln operated but we can make some assumptions based on other examples. There are three basic kiln designs; the simplest being an updraft arrangement whereby hot gasses rise through the kiln and out the hole in the roof. This sort of kiln was wasteful on fuel and gave unequal heat distribution as the hot combustion gases rushed too quickly through the kiln. The design was replaced by crossdraft (such as found at Wun Yiu and Tuen Mun with the dragon kilns) and down draft configuration, addressing the limitation of the original configuration. For both these newer solutions, a flue and chimney were required to control the air flow. It is understood that the Tai Om kiln used to have a chimney adjacent to the structure although this is no longer in place. In all cases, two further features were required, a fire box to generate the heat and a perforated floor to allow the hot gasses to escape. It is likely that the kiln had openings in the floor but these were removed or are now covered with debris.
As for the firebox, this could have been located below the debris in what is now the entrance. It may have been a brick structure with a grate to allow air to enter and ash to drop through, and for additional fuel to be loaded. The kiln would have used locally sourced wood as fuel, requiring over two tons of wood to achieve a fire temperature of 1,100° C.
Since hot gasses are lighter than cold air, a chimney is required to draw the air through the kiln, with the rising air pulling air in from the firebox. The higher and the larger the chimney, the more air will be drawn through the kiln. A rule of thumb for sizing is 3m of chimney for every 1m downward pull plus 1m for every 3.5m horizontal pull. Thus, for the Tai Om kiln, a chimney of around 13m, or 9m higher than the kiln would be required. This seems unlikely given the location and thus some other configuration may have been adopted.
The Tai Om kiln includes a number of side chambers located around the outside of the main structure. The chambers are a lined structure with their own chimney leading vertically up. Many kilns have access ports to assist in the firing operation, but given that there is no access to these chambers, they were probably used as the kiln flue. The holes are located at different levels, typically 600mm between each one, and this may have been a design feature to allow for a reduced chimney height, or to provide more control on the kiln temperature. It has been suggested that the inside of the kiln had several compartments dedicated to different items requiring different firing temperatures, hence the different flue levels.
The outlets for all but one of the chambers is visible on the surface as a 150mm-by-150mm brick hole, but this may not be part of the original details as it would not seem to meet the requirement of the chimney and may be as a result of some modification following the closure in 1900.
The central hole in the roof is unlikely to be part of the kiln firing operation as it does not provide a chimney function. It is more likely to be used to lower large items into the kiln and for cooling and allowing natural light into the chamber. During the firing process, it would have been covered with a stone or brick plug.
The kiln used locally sourced clay, excavated from the banks of the She Shan River and the adjacent hillside. Small scale excavations can be seen to the east of the kiln eating into the hillside.
In addition to construction materials of bricks and tiles, the kiln was known for the production of an eight-inch bowl decorated with a chicken motif called 大公. This bowl was rather unique as other kilns only produced a six-inch version.
The kiln came to the notice of the Antiquities and Monuments Office (AMO) in 2001 and it was noted that it required further investigation. More recent communications with the AMO resulted in the advice that “The dome-shaped kiln you mentioned is Tai Om Old Brick Kiln, a site of archaeological interest recorded by the Antiquities and Monuments Office (AMO). According to the villagers, the kiln was once used for firing bricks. As the kiln is situated on unallocated government land, we have been liaising with relevant government department to explore more protective measures for it. We have been conducting regular site inspections to the kiln to monitor its condition. AMO will provide comment and technical advice on development proposals that fall within or in the vicinity of the site so as to ensure the kiln is properly protected. Please rest assured that we will continue to upkeep the kiln.”
The kiln is in poor condition and the brick work is deteriorating particularly around the openings, trees are growing on the structure and there is a risk that if these are blown over, they may damage the structure. We can only hope AMO recognise that active measures are required to protect this link to pre-colonial village life.
So how exactly did the kiln function and what was its original design? only a detailed archaeological investigation and further local research would unlock these secrets..
The Self-Reliant Potter: Refractories and Kilns, Henrik Norsker
This article was first posted on 1st January 2022.
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