Pressing Pu'er: Steaming, Stone Molds, Machine Presses, and Compression
Turning loose tea into a round cake looks like a simple matter of "pressing it," but it's actually a whole sequence of steps: weighing, steaming, bagging, shaping, pressing, setting, drying, and wrapping. How a cake is pressed, and how tightly, affects its appearance, how easy it is to pry apart, and how quickly it transforms over the years that follow.
The Pressing Steps
1. Weighing
The maocha (or ripe tea) is weighed out to spec. A traditional round cake weighs 357 g. Some factories put the finer, prettier leaf on the surface as "face tea" and the sturdier leaf inside as "inner tea."
2. Steaming
The weighed tea goes into a steaming cylinder with holes in the bottom, set over boiling water. The steam makes the dry, stiff leaves soft and sticky so they can be pressed into shape. It doesn't take long, about half a minute, just until the leaves soften; steam it too long and the leaves get cooked and the aroma suffers.
3. Bagging and Shaping
The softened tea is poured into a cloth bag. The tea maker cinches the mouth of the bag and twists it a few times in their hands to shape the tea into a round mass; the spot where the bag is gathered becomes the "navel" (bing wo) on the back of the cake. The neifei (embedded ticket) is usually placed into the tea at this point and pressed in with it.
4. Pressing
There are several ways to do this:
- Stone pressing: the shaped tea is placed on a platform and a stone mold with a handle is set on top; a person stands on the stone and twists side to side, using their body weight to flatten the tea. The pressure is fairly gentle, so the cake has rounded edges, slightly uneven thickness, and moderate compression. This method has long been used in Yunnan's mountain areas.
- Jack or manual press: mechanical leverage applies more pressure than a stone, giving a flatter cake.
- Machine pressing: a hydraulic or pneumatic press applies strong pressure quickly, producing tight cakes of uniform size. Especially tightly pressed cakes look thick and hard and are often called "iron cakes" (tie bing).
5. Setting and Drying
The pressed cake sits in its cloth bag for a few minutes to set, then the bag is removed and the cake is laid on racks to dry. Some are air-dried indoors; others go into a drying room at low heat. Drying has to be thorough, since moisture left in the center of a cake can cause problems in storage. One study comparing ripe pu'er dried at different temperatures found that air drying and low-temperature drying below 60°C retained more of the tea's compounds and gave better quality, which suggests that in pu'er, "drying slowly" makes sense.
6. Wrapping
Fully dried cakes are wrapped in cotton paper, stacked 7 to a tong, wrapped in bamboo husk, and tied into a bundle. For what each kind of paper on the packaging means, read How to Read Pu'er Packaging.
Where 357 g Comes From
One cake weighs 357 g and 7 cakes make a tong, so a tong is about 2.5 kg. The story goes that 12 tongs made a basket of about 30 kg, and a horse carried two baskets, about 60 kg, which was just the right weight for the caravans. It's a vivid story, but no formal record confirms it, so it's best enjoyed as tea-table lore. For the name and history of the qizi bing ("seven-sons cake"), see From the Manshu to Tribute Tea: The History of Pu'er.
Loose vs. Tight
| Loosely pressed (mostly stone) | Tightly pressed (machine, iron cakes) | |
|---|---|---|
| Prying | Peels apart easily along the layers, strands stay whole | Needs a tea pick, breaks easily |
| Brewing | Releases flavor fast, opens up in the first few infusions | Water penetrates slowly, first few infusions need longer |
| Storage | More contact with air, transforms faster | Transforms more slowly and steadily |
| Best for | Watching the changes within a few years | Long-term storage and patient waiting |
Neither loose nor tight is better; it depends on how you want to drink it and how long you plan to keep it. Iron cakes are a chore to pry apart, but they're relatively stable to keep at home; stone-pressed cakes come apart easily, and you'll see their aroma change sooner.
Dragon Pearls and Small Tuo
Besides round cakes, pu'er is often pressed into small single-serving shapes. A dragon pearl is one session's worth of tea hand-rolled into a ball, then set and dried, so one pearl makes one brew; small tuo are pressed into a bowl shape with a small mold. These small portions don't need prying and tend to be pressed fairly tight, so give the first few infusions a little time to open up. For brewing tips, read How to Brew Dragon Pearls. Each of Guyuntang's Bingdao Old Village Dragon Pearls weighs 8 g.
Face Tea and Inner Tea
Carefully made cakes are layered: the surface uses attractive, bud-rich leaf called "face tea" or "sprinkled face" (sa mian), while the inside uses sturdier, fuller-flavored leaf called "inner tea." The face tea makes the cake look good; the inner tea gives the flavor its depth. When you pry a cake, you'll notice the tea on the surface looks a bit different from the tea at the center. That's by design. When brewing, take some face tea and some inner tea together for a more complete flavor.
Drying Is Key
Freshly pressed cakes are high in moisture and must be fully dried before wrapping. Yunnan processing guidelines recommend drying compressed tea at no more than 60°C, and the dried tea must meet the moisture standard: no more than 13% for raw tea and no more than 14% for compressed ripe tea. A cake that isn't dried enough can develop off smells in the center; drying too hot hurts the aroma. "Low heat, dry slowly" is a principle shared by many factories.
Reading the Pressing From the Outside
| What you see | What it may mean |
|---|---|
| Flat, smooth surface with sharp edges | Machine-pressed, even compression |
| Slightly uneven surface with rounded edges | Stone-pressed |
| Deep, distinct navel on the back | Firmly shaped in the cloth bag |
| Loose leaves falling off the surface | Lightly pressed, or absorbed moisture in storage and dried out again |
Tea Cake Weights
Besides 357 g, common round cake sizes include 100 g, 200 g, 400 g, and 500 g; bricks are commonly 250 g; tuo come in 100 g and 250 g, as well as small 3–5 g pieces. Smaller formats are handy for tasting and also make good gifts.
FAQ
How is an iron cake different from a regular cake? Iron cakes are machine-pressed especially tight, so they're hard and need a tea pick to pry apart. They transform more slowly than loosely pressed tea, and the first few infusions need a bit more time.
Why is a cake thicker in some places than others? Stone pressing relies on a person twisting their weight, so the pressure isn't perfectly even and the edges and center differ a little in thickness. That's a hallmark of hand pressing.
Does pressing affect the taste? The heat and pressure of steaming and pressing make the aroma a bit more subdued, and how fast the tea transforms in storage also depends on how tightly it's pressed.