Tan Bei (炭焙) is the traditional craft of roasting tea using charcoal. In Taiwan, the modern history of this craft can be traced back to when Chiang Kai-shek (蔣介石) settled in Taiwan. When Chiang Kai-shek retreated to Taiwan, he brought with him 48 masters of the Tan Bei roasting skill.
An interesting fact about these 48 roasters, is that they were almost exclusively employed to roast tea for government officials, including Chiang Kai-shek. The roasted tea they produced was called "Kuan-Pei"(官焙), which means "Official Roast". It wasn't until these masters passed on their craft to their heirs and students, that their roasting skills became available to the common Taiwanese people.
In the early years of tan bei roasting in Taiwan, the preferred tree for producing charcoal was the Taiwan Acacia (相思木). Taiwan Acacia has all the characteristics needed to produce high-quality charcoal for the roasting of tea; it doesn't produce much smoke, it doesn't impart much taste to the roasted tea, it doesn't irritate the mouth or throat, and the charcoal made from it burns at a constant, controllable rate. However, Taiwan Acacia wood is also rare, and thus became difficult to acquire. Because it has many of the same characteristics as Taiwan Acacia, Taiwan Longan (龍眼) was eventually chosen to be the new standard source of charcoal for tea roasting.
Above is a picture of the tan bei roasting holes. There is actually a special name for this style of tan bei holes. They are called Yin-Yang fire (陰陽火). Its meaning is that the ground balances out the temperature of the fire. This balance lets the roasting process become gentle, and avoids hurting the tea leaves. These holes are approximately 60cm deep, and have a diameter of 45cm; the distance between the holes is 15cm. These measurements might seem arbitrary, but they're actually crucial in producing high quality roasted tea. The volume of the holes, along with the spacing of them, allows us to produce the ideal temperatures and environment for roasting tea. For example, if the holes are spaced too far apart, the temperature while roasting will drop significantly over the roasting process. Of course, if they are too close, the temperature of the holes will be too high and over roast, or even burn, the tea.
In tan bei roasting, even simple things like these holes can make a big difference in the quality of the roasted tea.
Above Photos: Left - This is longan wood charcoal. For tan bei roasting, we need to break it down into smaller pieces. Right: Here were are in the process of hammering the charcoal into smaller pieces. We actually need to produce a variety of sizes: from somewhat thick, palm-sized pieces, to pieces that are thin and fragile.
After we finish breaking down the Logan charcoal, we have to prepare burnt rice husks (粗糠). The purpose of the rice husks is to light the charcoal, and provide a layer of insulation between the charcoal, and the tea leaves. The rice husks must be burnt, but not to the point where they become ash. This process takes 24 hours, and requires close monitoring to ensure the fire doesn't burn too hot, or too fast. We control the fire by turning over the rice husk pile every two hours. If we are unlucky and it rains, or there is too much humidity, we will have to start this entire process over. At the end of this process, we are left with beautifully blackened rice husks.
Once we finish hammering the charcoal and burning the rice husks, it's time to arrange the tan bei holes.
Even arranging the broken down charcoal in the tan bei holes is something that requires skill. We arrange the largest charcoal pieces in the bottom of the hole, and gradually use smaller and smaller pieces as we near the top of the hole. This arrangement of the charcoal results in the most even, long burning, fire once we start to roast. On top of the charcoal, we put the burnt rice husks.
Once the holes are arranged, we can light the rice husks. This method of lighting the rice husks, and not the charcoal, is the traditional way. Instead of lighting the rice husks, many modern tan bei roasters will directly light the charcoal using a blowtorch. This modern method has one main issue with it; it will cause the charcoal to burn too hot, too quickly. This is in contrast to the traditional method we use that allows the charcoal to burn slowly, and at a lower, more stable, temperature. However, with this traditional method, we must wait at least 24 hours until we can start roasting tea. 24 hours is how long it takes for the temperature in the tan bei hole to become stable, and suitable for the roasting of tea.
These photos were taken some time after lighting the charcoal husks. You can see that the husks have done their job and have ignited the longan charcoal. Now comes the crucial and time consuming step of controlling the rice husk ash. If we spread the ash out too thinly, the roasting temperature will become too high and hurt the tea leaves, and if we do it too thickly, the temperature won't be high enough to properly roast the tea. This is a key step in ensuring the quality of the roast will be high. To spread the ash out smoothly and to the right thickness is like a type of Gong Fu (功夫). When we spread the ash out, we must move our faces close to tan bei holes. While we do this, we can feel the fire and intense heat coming out of the holes.
Monitoring the tan bei process will be our life for the next 15 days. During this time we will not sleep much because we must always closely monitor the temperature of the tan bei holes. Every four hours, we must turn over the tea that is being roasted. On average, we will roast one bamboo basket worth of tea for 12 hours. Once one tea is finished, another will take it's place. We repeat this until the tan bei holes burn out.
In the bottom left photo above, you can see a bamboo basket with white powder all over it. This powder is actually caffeine that gets burnt out of the tea during the roasting process. If drinking tea makes it hard for you to sleep, we recommend drinking roasted tea.
The final step is to taste the tea. We will check if the tea is bitter or astringent, and whether it has a soft feeling in the mouth or not. If we find it to be bitter, astringent, or sharp in the mouth, it will need to be roasted again until these undesirable characteristics are gone.