8 June 2019

Visiting Anping: Oyster Shell Kiln Museum

It's our second time to be in Anping. 2 years ago we visited 5 most popular places which you can buy ticket in one time to visit. This time I wanted to see some placed we missed before. We visited Sio House (Salt Museum)Oyster Shell KilnTemple, Old Streetforts and castle and castle and some smaller ancient buildings. Some places are free of charge to visit, for others the entrance fee is 50NTD. Anping is one of my favourite places to visit, full of history and street food everywhere.
In March 2012, Anping was named one of the Top 10 Small Tourist Towns by Tourism Bureau of Taiwan. The older place name of Tayouan derives from nearby Taiwanese aboriginal tribe and was written by the Dutch and Portuguese variously. Han immigrants renamed the area "Anping" after the Anping Bridge in Fujian. Soon after Qing rule was established in 1683, the name "Taiwan" (臺灣) was officially used to refer to the whole island with the establishment of Taiwan Prefecture. 

Oyster Shell Cement Kiln Museum (安平蚵灰窯文化館)

Oyster Shell Cement Kiln (蚵灰窯) was once the most important building material factory in Anping. It's also the only surviving oyster shell kiln in Taiwan. From the 1600s, oyster shell ash was an essential material in boat-making for the many people in Anping who made their living from the sea. 
Later, sugar water and glutinous rice water were added to the ash to make the bricks and tiles for building houses. Anping oyster-ash kiln with its cubical exterior and domed interior is an unique structure. Its main weight-bearing structure is composed of red bricks, and is bigger than the average kiln. Its interior is approximately 4 meters in diameter, with a height somewhat higher than the average person. The thinnest sections of the walls are about 1 meter. 
In the museum you can learn about the oyster growing process and ecology, and oyster shell ash production process.
The birth of modern industry of lime in mass production in the 17-18th century made oyster-ash kiln gradually dismantled. Nowadays, it's only one oyster-ash kiln, which is completely preserved.

See also: Salt Museum

Oyster ash production process  

1. Bricks are laid out in rows along the bottom of the kiln to form gutters.The purpose of these gutters is to allow fresh air to flow into the kiln and sustain combustion.
2. Stone Shingles are laid on top of the gutters and then smaller shingles are used to fill the gaps between the larger shingles. They are loosely laid out to permit effective air convection.
3. Rice Straws are then placed on top of the shingles and used for ignition.
4. Fir Chips are laid atop the rice straws to feed the fire from the ignition of the rice straw
5. The burning flames from the fir chips and rice straws will then set the coal alight. The high temperature of the burning coal will leave the kiln smoldering for days. After the oyster-ash kiln is fired up, peddles are used to pump air into the kiln at a slow and constant rate to control the size of the fire. After the initial ignition of the rice straws and fir chips, air needs to flow into the kiln at a consistent pace to keep the coal burning. This fire had to be maintained for days for successful production of the oyster ash. Historically, workers took turns watching over the fire, and if necessary they pumped air into the kiln. However, with the advent of electric motors, their task has been simplified. 
6. Oyster shells which are carefully selected are then placed on top of the coal. The high temperature (500°C) will cause the moisture in the shells to evaporate. As the shells dry up, they decompose into oyster ash and carbon dioxide. These ashes can then be used as cement.
7/8. The coal and oyster shells are alternately piled on top of each other, and the amount of ash produced is dependent on the number of layers. 
The oyster ashes produced in the kiln are screened over a trench with an 80 to 100 count brass screen. Larger oyster ash particles are screened out and discarded, while fine oyster-ash powder is left behind in the trench. The fine powders are mainly used in building construction and are swiftly packaged for storage or delivery. If they are exposed to the open air for too long, they will significantly degrade from absorbing too much moisture and carbon dioxide.

Limestone and Tung Oil Cement

Quicklime, also known as Limestone is a sedimentary rock consisting of calcium carbonate. 
Limestone is typically grayish in color, but can be found in other colors. The rock turns into quicklime when heated to 800°C in the kiln. It reacts vigorously with water to produce slaked lime. Slaked lime is used as building material in modern days. Its function is similar to that of oyster-ash. Since slaked lime is cheaper and widely available, oyster-ash cement is now replaced by this modern material. 

Tung oil is extracted from the seeds of tung trees and has brownish color. The oil can be raw or heated and purified to produce thick oil. The raw oil is added with oyster ash and bitten until it becomes sticky. The tung oil oyster ash is more gel substance. 

No. 110之1號, Anbei Road, Anping District, Tainan City, 708

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