Wet Piling: How Ripe Pu'er Is Made

The deep red liquor and smooth, mellow taste of a cup of ripe (shou) pu'er come from a very visual step called wet piling (wodui). Sun-dried maocha is heaped into a small mountain, sprinkled with water, covered, left to wait, and turned. Forty-some days later, the green maocha has become reddish-brown ripe tea.

Where Wet Piling Came From

Traditional pu'er relied on time to age; a raw (sheng) cake had to sit for many years before its taste mellowed. In the 1970s, to make tea ready to drink sooner, Yunnan tea factories began researching ways to speed up fermentation artificially. It's generally believed that around 1973, the Kunming Tea Factory and the Menghai Tea Factory were the first to put wet piling into production. From then on, pu'er officially had a "ripe" branch.

The Wet Piling Process

Details vary from factory to factory, but the general steps are:

1. Sprinkling water: Water is sprinkled evenly over the sun-dried maocha so the leaves absorb the right amount of moisture. Too little, and fermentation won't get going; too much, and the leaves can turn mushy.
2. Piling: The leaves are heaped into a pile of a certain height, sometimes covered with wet cloth to hold in heat and moisture. The temperature inside the pile gradually rises as microbes go to work.
3. Turning: Every few days the pile is opened up, broken apart, and heaped up again so the inner and outer leaves ferment evenly and the temperature doesn't get too high. When to turn and how many times depends on the tea master's judgment by touch, smell, and color, and this is where experience is tested most.
4. Furrowing and drying: Once fermentation reaches the desired level, the pile is spread out and furrowed for airflow so the leaves dry slowly.
5. Sorting and picking: The leaves are graded by size and debris is picked out; then the tea is made into loose-leaf tea or steamed and pressed into shape.

The whole wet piling period usually runs forty-some days, adjusted for the season, the leaf grade, and the size of the pile.

What Happens to the Leaves in the Pile

Wet piling creates a hot, humid environment, with beneficial microbes such as Aspergillus niger and yeasts taking part. Much of the leaves' originally bitter and astringent content is transformed, producing substances such as thearubigins and theabrownins. As a result:

• The liquor goes from yellow-green to deep red;
• Bitterness and astringency drop noticeably, and the taste becomes mellow and smooth;
• The aroma shifts to gentle notes such as aged, woody, and jujube.

Light vs. Heavy Fermentation

Factories control the degree of fermentation depending on the style they want:

• Light fermentation: The liquor is a brighter red and keeps some of the leaf's own liveliness, with room to keep transforming in storage.
• Heavy fermentation: The liquor is deep and dark, the taste thicker and smoother, and the tea is very stable once finished.

Neither is absolutely better; it's a matter of style and preference.

What Is "Pile Taste"?

Ripe tea fresh from the factory sometimes has a smell like straw or damp earth, which tea drinkers call "pile taste." It comes from the wet piling process, and after some time in a clean, well-ventilated place it usually fades, leaving a cleaner, smoother brew. Rinsing the tea an extra time or two when brewing can also make the pile taste much lighter.

What you need to distinguish is this: pile taste is a scent left by wet piling, which is different from the musty smell of tea that has gotten damp. If a cake shows obvious mold spots, smells sharp, or the brew has an unpleasant sour, moldy taste, it was stored poorly, and you shouldn't drink it.

Grades and Raw Material for Ripe Pu'er

Ripe pu'er can be made from fine, tender leaf or from coarser, sturdier leaf. Ripe pu'er fermented from tender buds and leaves has lots of golden tips in the dry leaf and a fine, silky texture, and is often called "palace grade." Ripe pu'er made from larger leaves is fuller in taste, holds up to more infusions, and has obvious sweetness. Both have their fans, and neither is absolutely better.

Describing the Aroma and Taste of Ripe Pu'er

Good ripe pu'er is often described like this:

• Aroma: Aged, jujube, woody, and sticky-rice notes, sometimes with a touch of cocoa- or caramel-like sweetness.
• Liquor color: Deep, bright red, like a ruby when poured into a white porcelain cup.
• Taste: Mellow and full, smooth, sweet, with very little bitterness or astringency.
• Spent leaves: Reddish-brown and soft, with some springiness. If the spent leaves are black and hard and crumble when pinched, the tea was usually over-fermented.

The Numbers Researchers Measured in the Pile

In recent years, a research team tracked an actual ripe pu'er wet piling run and left a very concrete record:

• Time: The whole fermentation took about 30 days.
• Pile temperature: From day 3 to day 26 it was mostly between 51 and 63°C, dropping back to about 45°C near the end.
• Composition: Tea polyphenols fell from about 107 mg per gram to about 47 mg, a drop of more than half; theabrownins rose from about 18 mg per gram to about 61 mg.
• Microbes: Aspergillus niger dominated early on, and later Bacillus and a yeast called Blastobotrys took over.

These numbers show that wet piling isn't "leaving the tea to spoil," but a transformation with its own rhythm and division of labor. Yunnan's processing guidelines also recommend keeping the pile temperature at 65°C or below during fermentation to avoid scorching the leaves. The differences between light and heavy fermentation are covered in Fermentation Levels in Ripe Pu'er: Light, Heavy, and the Microbes in the Pile.

The Starting Point of Ripe Tea

The common account is that ripe tea was put into production around 1973 by the Kunming Tea Factory and the Menghai Tea Factory. Other sources record that Yunnan tea factories began experimenting with artificial fermentation in the 1960s, and that the process matured and was scaled up only in the 1970s. The years given vary slightly, but there is consensus that "the 1970s were the starting point for ripe tea."

A By-Product of Wet Piling

During wet piling, some leaves stick together into small clumps amid the heat, humidity, and turning. Picked out during sorting, these become lao cha tou ("old tea heads"), which are very sweet and hold up to many infusions.

FAQ

Can I drink ripe pu'er as soon as I buy it? Yes. Ripe pu'er is ready to drink once it's made. If you notice an obvious pile taste, you can break some off and leave it in a clean, ventilated place for a few days, or rinse it one extra time when brewing.

What water temperature should I use for ripe pu'er? Use boiling water at 100°C. Ripe pu'er needs high heat to bring out its aroma and body; if the water isn't hot enough, the brew will taste thin.

Is ripe pu'er good for cold brewing? Yes, cold-brewed ripe pu'er is smooth and round. We suggest giving it a quick rinse with hot water before cold brewing for a cleaner brew.

How long does wet piling take? It depends on the factory and the season; 30–45 days is common, and some methods take longer. One process measured by researchers took about 30 days.