What body is not
Three things get confused with it constantly. It is not strength, which is a matter of how much material is dissolved and can be raised simply by adding leaf — a strong tea can be thin and a delicate tea can be thick. It is not colour, which comes from a particular set of pigmented compounds and tracks oxidation more than texture; a pale gyokuro can have far more body than a dark supermarket black tea. And it is not astringency, which is the opposite kind of sensation — astringency is the removal of lubrication and body is the impression of substance, and a tea can have plenty of one and none of the other. Getting these separated is worth doing before trying to describe body at all, because most complaints that a tea is thin turn out on inspection to be complaints about something else. A fourth confusion is with temperature and with the sheer physical warmth of a drink, which contributes to an impression of fullness and disappears as the cup cools. Assessing body at two temperatures separates the two, and it is worth doing once because it recalibrates what a taster is attributing to the tea. The general lesson is the same one that governs every sensory dimension here: a quality that changes when something other than the tea changes was partly a property of the circumstances.
What contributes to it
Several things, and no single one explains it. The overall quantity of dissolved solids sets a floor: a very dilute cup cannot feel thick. Beyond that, the leaf’s polysaccharides — pectins and related material released during processing and steeping — are associated with viscosity and with a coating quality. Proteins and larger peptides contribute. Amino acids contribute a fullness that is distinct from viscosity and reads as roundness. In fully oxidised tea, the larger oxidation products behave as a colloidal rather than a simply dissolved fraction, which affects how the liquid feels as much as how it looks. And aroma contributes: a liquor with strong retronasal presence is consistently rated as fuller than a comparable one without, which is a perceptual effect rather than a physical one and is no less real for that. There is a further physical contributor that filtering makes visible. A liquor carries fine suspended material as well as dissolved material, and that fraction affects how the drink feels — which is why the same tea poured through a fine paper filter and through a coarse strainer produces two textures. Unfiltered preparations, whisked matcha most obviously, take this to its conclusion by suspending the whole leaf. Texture is therefore partly a decision made by the equipment rather than a property of the tea alone.
Why some categories have more of it
Older leaf and larger leaf material carry more of the structural polysaccharides, which is one reason mature-leaf teas such as shou mei and many hei cha give a thicker liquor than a bud-only tea of the same origin — and why the cheapest grade is sometimes the fullest. Long processing helps: extended withering, repeated rolling and bruising, and in dark tea the microbial phase all break down cell wall material and release more of it into solution. Compression and ageing continue that work over years, which is a large part of why an aged sheng is described as thick and an equivalent young one as sharp. Roasting has a complicated effect, adding a perceived density through aroma while removing some moisture-related qualities. Gyokuro and koicha reach thickness by an entirely different route, through very high leaf ratios and very high amino acid levels rather than through structural material. Stems and larger leaf material contribute in a way that cuts against the usual assumption that finer plucking is always better. Kukicha and other stem teas have a distinctive soft roundness that a bud-only tea from the same producer does not, and several categories are built around mature leaf specifically for the body it gives. Anyone who has decided that they prefer the cheapest grade in a range has usually decided that they prefer body, which is a coherent preference and not a failure of discernment.
What brewing does to it
More than most people assume. A higher leaf-to-water ratio raises body directly, and it does so without the shift towards the astringent late fraction that extending the time produces — this is the single most reliable way to make a thin cup fuller. Water matters: very soft or distilled water gives a flat, hollow liquor because some mineral content is needed for a full extraction, while very hard water flattens aromatics and adds grip instead. Vessel material has a measurable effect for some teas, and unglazed clay is traditionally used to soften and thicken a liquor. Filtering matters too: a cup poured through a very fine filter loses part of the fine suspended fraction and reads thinner, which is why the same tea from a gaiwan and from a paper-filtered brewer feels different. Temperature contributes as well, and in a way that complicates the usual advice. Hotter water extracts more of everything including the material that carries body, so a very cool steep chosen to protect sweetness can produce a liquor that is sweet and thin at once. Where a tea needs both, the usual answer is a higher ratio at the cooler temperature rather than a hotter steep, which is the same single-variable reasoning that governs every other brewing decision in this catalogue.
The vocabulary problem
English has few words for this and borrows them all from other materials: thick, thin, silky, oily, creamy, watery, round, structured. Chinese tea vocabulary is more developed — hou, thickness or depth, is a primary evaluative term, and hua, smoothness, is distinguished from it. TeaHQ’s mouthfeel vocabulary is deliberately coarse for the same reason all its controlled vocabularies are: it keeps `light`, `medium`, `full_bodied`, `silky`, `smooth` and `rich` as filterable facets while the free-text sensory notes carry the description worth reading. The coarseness is the point. A filter with twenty gradations of thickness would filter nothing, because no two people would place the same tea in the same bucket. Japanese tea vocabulary contributes its own terms again, with distinctions around smoothness and the sensation of a liquor passing down the throat that English handles clumsily. The recurring pattern across all three languages is that cultures which drink a great deal of tea without additions develop precise words for texture, and cultures that drink it with milk and sugar do not need them. English tea vocabulary is rich about strength and colour and poor about body for exactly that historical reason, which is worth knowing when reaching for a word and finding none.
How to learn to notice it
Body is the hardest sensory dimension to detect in isolation and the easiest to detect by comparison, so the method is comparative. Brew the same tea at two ratios and attend only to how the liquid feels, ignoring flavour entirely. Brew a bud-only white tea and a mature-leaf one side by side. Take a mouthful of water between sips as a reference. Some tasters find it helps to attend to what the liquid does after swallowing — whether it leaves a coating impression or disappears — since that is where the difference is starkest. Once noticed it is difficult to stop noticing, and it explains a good deal about why experienced drinkers rate teas the way they do, since body and aftertaste are consistently what separates a good example from an ordinary one in the same category. A useful trick for calibrating is to compare against something other than tea. Water, then a very dilute cup, then a full-strength one, gives a scale with a known bottom, and comparing a tea against skimmed and whole milk gives an exaggerated version of the dimension being learned. Once the sensation has been located it transfers immediately, and most people find they had been noticing it for years without having a name to attach it to.