Tang Boiled Tea · The Three Boils and Foam-Nurturing in The Classic of Tea

If you travelled back to eighth-century Chang’an and stepped into a teahouse, you would not see anything like modern “tea brewing.” Instead, you would witness a ritualised boiled tea (煎茶 / jiānchá) — the tea master casts fine tea powder (茶末 / chámò) into rolling water, adds a pinch of salt, and waits for a delicate white foam to bloom on the surface before ladling the broth, powder and all, into bowls. This is the Tang-dynasty tea method meticulously recorded by Lu Yu in The Classic of Tea.

Tang boiled tea was not merely a beverage; it was a complete social and cultural system. From imperial tribute teas to literati gatherings, from Zen monastic tea feasts to street teahouses, tea in the Tang completed its transformation from medicine and food to an independent drink. Lu Yu (733–804), later revered as the “Sage of Tea,” compiled his three-volume The Classic of Tea around 760–762 CE — the world’s first systematic treatise on tea and the most authoritative source for understanding Tang boiled tea[1].

The simulator above recreates the “three boils” of Tang boiled tea: from the first boil with tiny “fish-eye” bubbles, through the second boil’s “linked pearls” where tea is added, to the third boil’s “surging waves” and the nurturing of foam. Drag the slider or click the buttons to watch water temperature, liquor colour and operation steps change.

Social context of Tang tea drinking

The Tang dynasty (618–907 CE) marked the first golden age of Chinese tea culture. Before this, tea was mostly consumed as medicine or boiled together with other ingredients such as spring onion, ginger, jujube or mint. By the Tang, the rise of Chan (Zen) Buddhism and the expansion of the civil-service examination system had created a large literati class. Tea, prized for its mind-focusing and fatigue-dispelling properties, became a shared passion of scholars, monks and aristocrats.

The imperial tribute-tea system was formally established in the Tang. According to the New Book of Tang · Geography, more than ten prefectures presented tea as tribute, with Guzhu Zisun (顾渚紫笋 / purple bamboo shoot) the most celebrated. Every year before Qingming, the “Tea Manufactories” of Changxing (Zhejiang) and Yixing (Jiangsu) would rush the finished tribute tea to Chang’an by post-horse relay — the so-called “urgent-schedule tea”[2]. This system drove standardisation and refinement in tea production, and supplied Lu Yu with abundant material for writing The Classic of Tea.

Literary tea gatherings also flourished. Bai Juyi, Yuan Zhen, Liu Yuxi and others left behind a rich corpus of tea poetry[9]. Tea was not only a drink but a social medium and spiritual symbol — a thread that would continue through Song whisked tea and Ming steeped tea, though the forms kept evolving.

Lu Yu and The Classic of Tea

Lu Yu, styled Hongjian, travelled through Jingchu and Wuyue, investigated tea affairs, and finally settled by the Tiaoxi Stream in Huzhou (Zhejiang) to write his book. The Classic of Tea is divided into three volumes and ten sections: Origin, Tools, Making, Utensils, Boiling, Drinking, History, Production Regions, Omissions (simplified variants), and Diagram (to be copied on silk and hung on the wall for reference)[1].

The section “On Boiling” (五之煮) is the core chapter for understanding Tang boiled tea. Lu Yu gives detailed rules on water quality, fuel, utensils, fire control, timing of tea addition, and salt quantity — displaying a high degree of empirical rationality. For example, he ranks water as “mountain spring best, river water medium, well water lowest,” and specifies that mountain water should be chosen from “slow-flowing spring pools among rocks” — an intuition that aligns remarkably well with modern water chemistry concerning mineral content and dissolved oxygen[3].

Boiled-tea utensils: brazier, boiler, ladle and scoop

In the “Utensils” chapter (四之器), Lu Yu lists twenty-four implements. The core boiling set includes:

Figures are representative ranges. Materials and dimensions varied by region and social class in the Tang[1][4].

The design of these utensils reflects a sophisticated synthesis of heat conduction, fluid stirring and visual aesthetics. The boiler’s wide mouth and shallow body facilitate rapid evaporation and bubble observation, consistent with modern heat-transfer principles of increasing evaporative surface area and promoting natural convection; the scoop’s ring shape allows gentle circulation without destroying the foam structure[1][10].

The three boils: physics and chemistry

Lu Yu’s description of water heating is one of the most detailed records of boiling in ancient Chinese literature. He divides the process into three stages:

From a modern physico-chemical perspective, these three stages correspond to the typical evolution of bubble nucleation and fluid convection during heating:

First boil (approx. 80–85 °C)

At this point the water is close to boiling. Dissolved gases (mainly nitrogen and oxygen) come out of solution as solubility drops, forming tiny bubbles at nucleation sites on the vessel wall — exactly what Lu Yu observed as “like fish eyes, with a slight sound.” Natural convection dominates, and a temperature gradient is still present[5].

Lu Yu instructs adding salt at this stage. Salt (NaCl) not only seasons the broth but also slightly raises the boiling point (by roughly 0.5 °C per 3 g salt in 100 g water) and changes ionic strength, affecting the subsequent extraction rate of tea compounds. The Tang used mostly rock or well salt; the quantity was small, about 0.5–1.5 g per 200 ml, just enough “to harmonise the taste” rather than to make the broth salty[1].

Second boil (approx. 90–95 °C)

Bubbles grow larger and rise faster, forming “linked pearls” along the rim. Convection intensifies and the water temperature becomes more uniform. Lu Yu instructs scooping out one ladle of water for later use, then “stirring with the bamboo scoop and casting tea powder into the centre.”

Chemically, 90–95 °C is the temperature range where most soluble tea compounds extract efficiently:

• Tea polyphenols (catechins) extract rapidly, reaching 60–80 % of equilibrium concentration within about 1–2 minutes[6];
• Caffeine dissolves quickly, contributing bitterness and stimulant effect;
• Amino acids such as theanine extract gently, providing umami freshness;
• Proteins and polysaccharides partially dissolve, laying the material foundation for the later foam.

Tang tea powder was made by roasting a compressed tea cake, grinding it, and sifting it through a fine sieve. The particle size was roughly 0.1–0.5 mm, offering a large surface area for rapid extraction. The dosage was about 1–3 g per 200 ml (Lu Yu measured it with the “ze,” roughly 1.5–2 g per measure)[1][4].

Third boil (approx. 100 °C)

Water reaches its boiling point at atmospheric pressure; violent vaporisation produces turbulent “surging waves.” Lu Yu stresses that “beyond the third boil the water is aged and unfit to drink” — prolonged boiling drives dissolved oxygen out of the water, making it taste flat, while excessive heat and time can over-oxidise catechins and cause caffeine-polyphenol complexes to precipitate, darkening the colour and coarsening the taste[5][6].

At this point the water reserved from the second boil is poured back. This quickly lowers the overall temperature below 95 °C, halting violent boiling, and promotes the formation of a stable surface foam layer — what Lu Yu calls “mobo.”

Mobo (foam) and nurturing the bloom

Mobo (沫饽) was the most aesthetically prized element of Tang boiled tea. Lu Yu classifies it into three grades:

• Thin foam: like jujube flowers drifting on the edge of the pool;
• Medium foam: like duckweed floating at the water’s margin;
• Thick foam: like accumulated snow or frosty mist.

Modern analysis shows that foam stability depends on the synergistic action of tea saponins, proteins and polysaccharides. Tea saponins are natural surfactants with strongest foaming activity at 90–100 °C; proteins and polysaccharides increase viscosity and half-life of the foam[7]. The Tang practice of “yuhua (育华 / nurturing the bloom)” — cultivating and admiring this foam — was a critical step; its thickness, persistence and colour directly reflected the quality of the tea powder and the skill of the brewer.

Differences from modern boiled tea and steeping

Figures are representative ranges; practices vary by region and school[1][4][8].

The fundamental difference between Tang boiled tea and modern steeping lies in the inseparability of “powder” and “broth.” Because the powder was extremely fine, it could not be filtered out as in later methods; the Tang people “ate tea” rather than simply “drank tea.” This mode of consumption persisted through the Song dynasty’s whisked tea (still using powder, beaten with a bamboo whisk) until the Ming dynasty, when the Hongwu Emperor abolished compressed tribute cakes in 1391 and loose-leaf steeping gradually became dominant.

Flavour profile

The flavour of Tang boiled tea was quite different from modern plain steeping: salt adds a subtle savoury note, the fine powder gives the liquor a certain thickness, and the foam contributes a creamy mouthfeel. Because the compressed cakes were lightly roasted during preparation, the broth tended to carry toasted and caramel notes rather than the fresh floral aroma of modern green tea[10].

The profile is schematic, based on The Classic of Tea and modern reconstructions of Tang cake-tea chemistry. Actual results vary with cake origin, roasting degree, water quality and brewing skill.

Common misconceptions

1. “Tang boiled tea is the same as Japanese matcha.” Both use powdered tea, but matcha is made from steam-fixed tencha, is not boiled, uses no salt, and prizes ultra-fine foam. Tang boiled tea uses roasted cake powder, adds salt, and the powder is consumed with the broth. The techniques and aesthetics differ significantly[8].
2. “Lu Yu opposed adding salt.” Lu Yu did criticise boiling tea with “spring onion, ginger, jujube, orange peel, evodia or mint,” but The Classic of Tea explicitly records adding salt at the first boil: “When the first boil is reached, adjust the taste with salt”[1].
3. “You can keep boiling after the third boil.” Lu Yu clearly states that “beyond the third boil the water is aged and unfit to drink.” Sustained boiling drives off dissolved oxygen and degrades tea quality — a view consistent with modern water chemistry[5].
4. “Boiled tea was the only Tang drinking method.” Boiled tea was the dominant literati method, but folk variants such as “pickled tea” (similar to fermented leaf) and “cooked tea” (with multiple spices) also existed. Lu Yu recorded the refined “plain drinking” method favoured by scholars[1][4].

Related entries

• Song whisked tea — the evolution from boiled tea to whisked tea
• Origin and global spread — tea’s historical trajectory from medicine to global beverage
• Tea Horse Road — the key trade corridor for Tang-dynasty tea
• Science · Leaf Chemistry and Flavour — the chemical foundations of tea liquor

References

1. Lu Yu. The Classic of Tea (茶经). c. 760–762 CE. (Modern edition: Wu Juenong, ed. Commentary on The Classic of Tea. China Agriculture Press, 1987.)
2. Li Zhao. Supplement to the History of the Tang (唐国史补). Tang dynasty. Records Guzhu Zisun tribute tea and the “urgent-schedule tea” system.
3. Zhu Zizhen. Selected Historical Materials on Chinese Tea. Agriculture Press, 1981. Collects The Classic of Tea and other Tang tea documents.
4. Chen Zongmao, ed. Encyclopedia of Chinese Tea. China Light Industry Press, 2000. Entries on Tang tea utensils, tribute tea and drinking customs.
5. Vollmer, M., & Möllmann, K.-P. (2012). High-speed imaging of bubbles in boiling water. European Journal of Physics, 33(6), 1737–1746. Physics of bubble nucleation and convection during boiling.
6. Spiro, M., Jaganyi, D., & Broom, M. C. (1992). Kinetics and equilibria of tea infusion. Part 9: The rates and temperature coefficients of caffeine extraction from green Chun Mee and black Assam Bukial teas. Food Chemistry, 45(5), 333–335. Caffeine extraction rates at different temperatures (temperature coefficients).
7. Liang, Y. R., & Lu, J. L. (1992). Tea saponins and their foam stability. Journal of the Science of Food and Agriculture, 58(2), 249–253. Foaming properties and stability mechanisms of tea saponins.
8. Kuwata, T. History of the Japanese Tea Ceremony. University of Tokyo Press, 1980. Comparative study of Chinese and Japanese tea culture.
9. Bai Juyi. Bai Juyi Ji (Collected Works of Bai Juyi). Collated by Gu Xueji. Zhonghua Book Company, 1979. Contains poems such as “Qin Cha” and “Thanking Li Liangong for Sending New Shu Tea,” important records of Tang literati tea culture.
10. Chen Zongmao, ed. Encyclopedia of Chinese Tea. China Light Industry Press, 2000. Entries on Tang tea utensils, tribute tea and drinking customs; roasting craft and flavour characteristics of cake tea.