August 08, 2018

We're Building an Experimental Pu-erh Storage Room

We're Building an Experimental Pu-erh Storage Room

The question of how to store your tea is almost as important as how to brew it. Strong odors nearby, from kitchen foods or aromatic wood cabinets, can insinuate themselves onto the leaves. Direct light can drain even high-quality tea's color and vitality over time; excessive ambient heat or humidity can degrade the fragile volatile compounds in the leaves.

Our tea is kept in airtight packaging, at our climate-controlled warehouse, to keep these issues at bay. But when it comes to storage, one type follows its own complicated rules: pu-erh. This post-fermented tea from Yunnan Province is processed at a lower temperature than Chinese green tea, which means enzymatic oxidation and microbial fermentation continue in the leaves even after the tea is fully dried. In other words, pu-erh tea ages over time, and the environment in which it ages contributes substantially to the tea's final character. If you took two pu-erh bingchas from the same production lot and stored one in Seattle for 10 years, and the other in Shanghai, you would wind up with two distinct drinking experiences when cupping them side by side.

Unlike other categories of tea, pu-erh thrives in high heat and humidity. The warmer and muggier the climate, the more quickly pu-erh leaves will oxidize and ferment, and the more dramatic the evolution in flavor and fragrance can be. On the other hand, too much heat and humidity can foster mold growth. This is why pu-erh collectors pay close attention to their storage environment: pu-erh that you intend to age yourself is an investment, and you don't want that investment ruined by dry air or bacteria-coated bingchas.

Pu-erh Storage

The more you learn about pu-erh storage, the more you realize how much there is to know—especially in our Western tea-drinking community, where, apart from the heroic efforts of hobbyists tinkering with their own designs, we simply don't have much empirical evidence about how pu-erh stored in the U.S. will evolve.

Conventional pu-erh wisdom says the northeast U.S. is too cool and dry to successfully age it over the long term. From our experience, pu-erh we've stored here for five or ten years have certainly changed more slowly than they would in muggier parts of Asia. This is why, for the past few months, I've been doing some construction.

I've cordoned off a corner of this basement to create a sealed, climate-controlled pu-erh storage room capable of maintaining heat and humidity with minimal interference. The specifications:

  • The radiant-heat wood floor can be adjusted to specific temperatures. To start, I've set it at 70°F (21°C), to warm the room up.

  • Insulation is provided naturally by two foot-thick stone walls, and by foam in the other two wooden walls, ceiling and floor.

  • The concrete channel along at the base of the stone walls funnels excess condensation out of the room.

  • A dehumidifier keeps the room at 55% relative humidity. To increase the humidity, I can splash some water on the stone wall.

  • The room gets occasional air exchange when I open the sealed door for a weekly check-in.

As I load in more tea, I'll likely raise the initial temperature to more closely replicate the climate of southeastern China—the traditional capital of pu-erh storage—but the energy cost to maintain an 80° F room is much higher than 70° F. So far I've been focusing on establishing a temperature and humidity baseline—and letting the microorganisms in all these teas get to know each other.

These are all from my personal stash, and I plan to taste how they're progressing every three to four months. Once I'm confident that the room is doing good things for the tea, we'll begin moving our retail and wholesale pu-erh stock in as well.

But I'm most excited about the prospect of collecting data: cupping identical bingchas stored in my room and in our warehouse; creating microclimates in the room to replicate specific, sought-after aging environments such as Xishuangbanna and Hong Kong; sharing samples with other pu-erh drinkers across the U.S. to compare notes. If tea purveyors like us seek to grow the American pu-erh market, Asian sources will only take us so far. We also need to build our own base of knowledge, which means experimental setups like this.

And it already smells really, really good.

More in-depth reads on pu-erh storage