The Primary Processing of Tencha
Sencha is a type of green tea finished into a needle-like shape by repeatedly rolling the tea leaves, which presses out the internal moisture while drying them. By intentionally breaking the cellular structure of the leaves, it becomes easier for the flavor to dissolve into the water when brewed. On the other hand, Tencha completely skips this rolling process. This is because Tencha is ultimately ground into a fine powder using stone mills to be enjoyed as Matcha.
① Steaming (Jōnetsu)
Both Tencha and Sencha share the same starting point: steaming. To prevent the tea leaves from oxidizing, they must be steamed as quickly as possible to halt the oxidation (fermentation) process. This is a characteristic shared by all Japanese green teas. The steaming time for Tencha is usually set between 15 to 20 seconds, which is shorter than that of standard Sencha. Because shade-grown tea leaves (used for Tencha) are thinner than those grown under direct sunlight (open-field cultivation), heat penetrates them much faster. Steaming them briefly prevents over-steaming and preserves Tencha's vibrant green color and distinct ooika (shaded aroma).
② Cooling & Separation (Sanchaki / Leaf Disperser)
The steamed leaves are sent to a machine called a Sanchaki (leaf disperser). This machine serves two main purposes:
- To cool down the steamed tea leaves and remove the residual heat.
- To separate and spread out overlapping leaves evenly, ensuring uniform drying in the next step inside the Tencha furnace.
Air is blown from underneath, shooting the tea leaves high up into the air. As they fall back down, the clumped-up leaves naturally separate and scatter evenly onto a conveyor belt.
③ Drying (Horii-style Tencha Furnace)
The tea leaves are placed into a large, brick-enclosed furnace to dry. The inside of the furnace is structured with 3 or 4 tiered levels; the leaves are first dried at the bottom level with the strongest heat, then moved to the upper tiers to dry slowly and thoroughly. The temperature inside the furnace reaches a high heat of about 180°C or 200°C, and the leaves are dried for about 30 minutes. The intense heat generated by this furnace is the reason why Tencha factories are extremely hot inside.
The brick-enclosed Horii-style Tencha furnace utilizes "radiant heat" near the furnace opening and "convection heat" further away from the heat source to dry the leaves. This process produces a unique roko (toasted furnace aroma), a beautiful color and sheen, and exceptionally high-quality Tencha. Conversely, the recently developed Net-style Tencha furnace offers the advantages of being more space-efficient and having a higher hourly production rate than the Horii-style furnace. However, it differs in that it is prone to uneven drying.
④ Cutting & Separation (Tsurutori-ki / Stem Separator)
Although the tea leaves coming out of the Tencha furnace are mostly dry, the stems still retain a lot of moisture and take longer to dry. Therefore, the stems and leaves must be separated. The stem portion is not used when grinding Matcha; instead, these stems are typically repurposed to make Hojicha (roasted green tea) or Kukicha (stem tea).
The History Behind the Innovation
The Horii-style Tencha furnace was developed in 1924 by Chojiro Horii, the head of the Horii Shichimeien tea estate. Before its invention, all Tencha processing had to be done entirely by hand, which required immense labor and presented immense technical difficulties. Leaves were dried by hand, spread flat over traditional Japanese paper called Hoiru-gami while heat was applied underneath. The temperature of this paper reached about 120°C, and because the drying process took a very long time, it was grueling manual labor that made uniform drying incredibly difficult. Furthermore, separating the stems from the leaves had to be done visually by women, one by one—a task requiring an astronomical amount of time and effort.
While Matcha has become a very familiar part of our daily lives today, we owe it entirely to these kinds of technological innovations. Knowing this history helps us truly appreciate just how much of a luxury product Matcha used to be—an expensive delicacy that only a select few of the upper class could enjoy.
