tea finishing fire (hi-ire)
process / process-tea-hiire
火入れ
Finishing heat treatment applied when crude tea is made into finished tea. It develops a roast aroma and taste while drying moisture from the leaves.
On this page (7 sections)
Reading the bitterness
Firing (hiire) is the finishing heat treatment that turns crude tea into finished tea, developing the aroma and taste distinctive of fired tea while drying it. Technical information from the Kochi Prefectural Agricultural Technology Center Tea Experiment Station gives the sequence for finishing locally produced normally steamed sencha: grading, sorting, firing, then blending. It describes firing grade A crude tea to preserve its superior appearance and inner quality (about 90°C for 30 minutes in a rotary-drum firing machine, or about 100°C for 20–30 minutes for a light roast aroma). For grades B and C, it describes firing that adds a medium to strong roast aroma (about 100°C for 30–40 minutes) to emphasize the taste and aroma distinctive of fired tea. Excessive firing is described as generating a burnt smell that masks sweet aroma.
The center evaluated grade A crude tea fired in a small rotating-drum firing machine adapted from a Collins roaster at combinations of tea temperature 90–120°C and 10–40 minutes. At 90°C for 10 minutes, its aroma score (on a 9-point scale) was 4, roast aroma 0, and burnt smell 0; at 120°C for 40 minutes, aroma was 9, roast aroma 4, burnt smell 1, sweetness of aroma 2, and sweetness of taste 3. Roast aroma and burnt smell both intensified with higher temperature and longer time. Grade C tea showed a similar trend, but its aroma score at 90°C for 10 minutes was only 2, below grade A (4) under the same conditions. The evaluation addressed sweetness of aroma, sweetness of taste, roast aroma, and burnt smell; the consulted source did not show a scale for bitterness itself.
In a separate 2014 trial, when honcha (the main sieved tea leaves) and powdered tea were fired separately, sensory judging (liquor color, aroma, and taste each out of 20 points, by consensus of 5 tea professionals) rated 100°C for 30 minutes in a shelf dryer highest at 60 points, above 90°C for 30 minutes (57) and 110°C for 30 minutes (54). When honcha and powdered tea (10% by weight) were fired together, 90°C for 30 minutes ranked highest at 58 points, above 100°C for 30 minutes (54). Comparison of the 2 tables thus shows a different temperature for the top sensory rating depending on whether honcha is fired alone or together with powdered tea.
On heat sources, a tea merchant's explanatory article says from experience that charcoal gives 「香りが素直」 (in translation: "a straightforward aroma") and is 「面で温めやすい」 (in translation: "easy to heat across a surface"), but requires ventilation and ash management. The article also says that each 10°C rise in firing temperature increases aroma release and the likelihood of astringency. This is an experiential rule without measured data, and concerns astringency rather than bitterness itself. In hand-rolled tea making, registered as an Intangible Cultural Property in 2024, a tool called jotan (a wooden frame with washi on its underside) is placed over a drying furnace called a hoiro to transfer heat, and the leaves are dried while shaped with various hand movements. The Agency for Cultural Affairs account does not specify whether charcoal fuels the hoiro.
Sources for this overview
Checked for this overview: Used as evidence for the process order and recommended firing temperatures and times. / Used as evidence for grade A sensory ratings by temperature and time. / Used as evidence for comparison with grade C tea.
土佐茶の深蒸し茶の火入れ方法および普通蒸し茶とのブレンド割合
Checked for this overview: Used as evidence for rating data when honcha was heated alone. / Used as evidence for score comparisons when honcha and powdered tea were heated together.
Checked for this overview: Used as evidence for the experiential account of charcoal firing.
Checked for this overview: Used as evidence for the account of the hoiro and jotan in hand-rolled tea making.
Structured claims — open a section to read each claim's confidence, evidence and limits
Sensory (4)
Scope: Grade-A crude tea (from Kochi Prefecture, 50-second steaming time).
Note: The infusion was prepared with 4g of tea leaves, water at 80 C, 140 ml of water, and an 80-second steeping time, then tasted. Aroma was evaluated by sensory assessment of the scent of 4g of tea leaves steeped in 140 ml of hot water. The number of evaluators is not stated.
Show data
process-tea-hiire —has_sensory_response→ "Using a small rotating-drum firing machine (with tea-temperature control) modified from a Collins roaster, grade-A crude tea was fired at combinations of tea temperature 90, 100, 110, and 120 C and time 10, 20, 30, and 40 minutes, and aroma (9-point scale, 5 being favorable) and the infusion (roast aroma 0-4, burnt smell 0-1, sweetness of aroma 0-3, sweetness of taste 0-3) were evaluated (2020). At 90 C for 10 minutes, the aroma score was 4, roast aroma 0, burnt smell 0, sweetness of aroma 0, and sweetness of taste 0, whereas at 120 C for 40 minutes the aroma score was 9, roast aroma 4, burnt smell 1, sweetness of aroma 2, and sweetness of taste 3 -- roast aroma and burnt smell intensified as temperature and time increased."Scope: Grade C crude tea (from Kochi Prefecture, steamed for 50 seconds).
Note: The evaluation method was the same as for grade A (2020).
Show data
process-tea-hiire —has_sensory_response→ "When grade C crude tea was evaluated by the same method, at 90°C for 10 minutes its aroma score was only 2, roast aroma 0, burnt smell 0, sweetness of aroma 0, and sweetness of taste 0. Its aroma score was below grade A under the same conditions (aroma 4, roast aroma 0); both had a roast-aroma subscore of 0, with no difference. At 120°C for 40 minutes, aroma was 9, roast aroma 4, burnt smell 1, sweetness of aroma 1, and sweetness of taste 3."Scope: Crude tea made from 「やぶきた」 (Yabukita) (52% bud opening), brought to JA Cosmos Niyodo First Tea Factory on May 3, 2014.
Note: The judging bowl received 5 g of tea leaves and 200 ml of water at 70°C; aroma was judged immediately, and liquor color and taste after 90 seconds of infusion.
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process-tea-hiire —has_sensory_response→ "In 2014 sensory judging of honcha (the main sieved tea leaves) and powdered tea fired separately (maximum 20 points per attribute, consensus of 5 tea professionals), honcha fired in a shelf dryer at 100°C for 30 minutes scored 20 for liquor color, 20 for aroma, and 20 for taste, totaling 60, the highest rating; it exceeded 90°C for 30 minutes (57 total) and 110°C for 30 minutes (54). Powdered tea scored highest at 59 after 80°C for 60 minutes (70°C for 60 minutes: 58; 90°C for 60 minutes: 54). In a rotary firing machine, honcha scored highest at 60 after 90°C for 40 minutes (80°C for 40 minutes: 57; 100°C for 40 minutes: 54)."Scope: The same 「やぶきた」 (Yabukita) crude tea (10% powdered tea).
Note: The different optimal temperatures for separate and combined firing come from comparing 2 tables (Tables 1 and 2) in the report.
Show data
process-tea-hiire —has_sensory_response→ "When honcha and powdered tea (10% by weight) were fired together, 2014 sensory judging gave the highest shelf-dryer rating to 90°C for 30 minutes: liquor color 20, aroma 19, taste 19, total 58, above 100°C for 30 minutes (54 total) and 110°C for 30 minutes (53). In a rotary firing machine, 90°C for 40 minutes ranked highest at 58 (80°C for 40 minutes: 57; 100°C for 40 minutes: 50). Honcha fired separately rated higher at 100°C, whereas the combined tea rated higher at 90°C."How processing and cooking change it (1)
Scope: Crude ordinary steamed sencha produced within Kochi Prefecture.
Note: Extension technology information from the Kochi Prefectural Agricultural Technology Center Tea Experiment Station (research period: Heisei 30 to Reiwa 2).
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process-tea-hiire —is_prepared_by→ "Finish processing of crude tea produced within the prefecture (ordinary steamed sencha) proceeds through the stages of grading → sorting → firing (hiire) → blending. After the crude tea is graded by inspection into Grade A (for high-grade tea), Grade B (for mid-grade tea), and Grade C (for ordinary tea), Grade A crude tea, whose appearance and internal quality are superior, is fired to make the most of that character, at around 90°C for 30 minutes in a rotary-drum firing machine, or, when adding an even lighter roast aroma, around 100°C for 20-30 minutes. Grade B and Grade C are fired with a medium-to-strong roast aroma, to generate the taste and aroma distinctive of fired tea and emphasize its toastiness, at around 100°C for 30-40 minutes in a rotary-drum firing machine. Firing is a heating process that generates the aroma and taste distinctive of fired tea, and excessive firing masks the sweet aroma with a burnt smell."Culture (2)
Scope: General explanation by the tea merchant 「スズキの製茶」 (Suzuki no Seicha).
Note: An explanatory article based on a tea merchant's experience, with no measured data or sources cited. It does not discuss the effect of charcoal specifically on bitterness or astringency.
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process-tea-hiire —is_presented_as→ "In comparing heat sources for firing, a tea merchant's article cites charcoal's advantages as 「香りが素直」 (in translation: "a straightforward aroma") and 「面で温めやすい」 (in translation: "easy to heat across a surface"), while noting 「換気と灰の管理が必要」 (in translation: "ventilation and ash management are necessary"). It also states of firing temperatures generally, 「温度+10℃は香り立ち↑、渋みの出やすさも↑」 (in translation: "a temperature increase of 10°C heightens aroma release and the likelihood of astringency")."Scope: Hand-rolled tea making (Registered Intangible Cultural Property).
Note: The original Agency for Cultural Affairs account does not state the material of the hoiro's heat source (whether it is charcoal).
Show data
process-tea-hiire —is_prepared_by→ "Hand-rolled tea making (registered as an Intangible Cultural Property on December 16, 2024) uses a drying furnace called a hoiro and a jotan (a tea-making tool with washi attached to the underside of a wooden frame) placed above it to transfer heat to the leaves. Various hand movements shape the leaves as they dry."