Kilns for Firing a Yixing Teapot

There were two types of kilns historically used in Yixing: Snake Kilns and “Modern Tunnel” Kilns. Later, gas and electric kilns came to be used instead.

Snake kilns were used throughout China for thousands of years, and the only type of kiln in use up to 1957. Snake kilns are simple, single-column climbing kilns made of clay and brick with a frontal firing chamber, air and fuel ports along the side, and a tall chimney at the far end. The kiln is set on a slope with the chimney at the highest point, which causes a consistent oxygen flow due to the heat rising up the slope and out of the chimney. These kilns could be up to 60 meters long and burn for over a week (though they would have been shorter and faster for yixing firings).

burn baby burn!

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Basic Verification of Yixing Teapots

calligraphy on a teapot; flowing liquid poetry; I want more tea to speak to me

Yixing teapots have been in nearly continuous production (wars being the primary cause of discontinuity) since the Song dynasty, reaching the height of their production during the Qing dynasty, before the market became flooded with teapots made from other clays.

The increase in price and rarity of real yixings of known provenance has caused a ripe market for fakes – often an expensive mistake for new and experienced practitioners alike. Simple fakes are often made from clays other than Yixing, and are not particularly hard to identify.

The better “fakes” can be real Yixing – but from the wrong year or maker. Most yixing teapots were made by students and apprentices of masters, who learned to make teapots by copying the designs of the masters before them. Masters from previous dynasties would have both later masters and their students copying their designs – “fakes” existed as early as the Ming Dynasty, with potters copying master made pots from the Song Dynasty. Students and apprentices copied their masters’ designs using the same tools, clay, and kiln. Thus, most master made pots would have been copied at least 10 times by students in training, using identical clay and equipment.

Are all of these teapots fakes? No – that would be a poor definition of “fake”…. Do yixings need to be master made to be real? No – they simply need to improve the tea you decide to pair with it to be used within GongFu.

Thus, even if one knows how to determine the composition of the clay (yixing vs. not yixing) by hand or through an analytical test, determining the age and provenance is still a challenge (for example, you can’t use radio-carbon dating on clay…. clay is really very old).

A practitioner of tea who wishes to purchase yixing for GongFu must learn a set of methods to separate real from fake. This first post will explain.

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Buddha wasn’t a Buddhist

It’s a poetic anomaly,
There is no right theology,
It’s phenomenology you need to Witness the reality:
No koan spoken understood;
No vista below the gaze undertook;
No path you know underfoot;
The crucible denied because even though you tried the reality you saw was caused by the illusions you had in mind – it was but shadows on the wall, hinting at a larger picture beyond, an impermanent veil instead of all… you could see, if we just opened our eyes, maybe for the first time.

This poem uses Buddhist philosophy to argue against certain Buddhist beliefs structures. The specific beliefs are left as an exercise to the reader.

Processing of Yixing Clay

The raw yixing dirt needs to be processed and refined before it can be fired into a beautiful, usable, teapot. The clay starts as a dusty, soft, colorful dirt and goes through 8 processing steps that can take up to 50 years to complete – the longer the clay is aged and rested, the higher the quality (and the less likely it is to break in the kiln from uneven shrinkage caused by impurities).

This process list only applies to higher quality yixing clay. Obviously, lower quality yixing clay (and fake or fraudulent clay) cuts corners and the aging and resting process.

The Process:

  • The clay-dirt is left out in the elements (for a long time) to dry. The particle size of the uncompressed clay is quite small, and the clay should be spread out over a wide area.
  • The drying process (and mallets) breaks down the clay into even smaller particles. This makes it easier to sift and remove impurities.
  • The Yixing continues to rest and soften for a minimum of 2+ years (usually about ~3 years).
  • The clay is dry milled into sand. (this is where the term purple sand for Zisha Yixing comes from)
  • The sand is sifted with water down to 30 microns (the laborers where respirator masks). This continues to remove impurities and pieces of yixing that haven’t broken down.
  • The artist or yixing master blends refined sands from multiple areas. The mixture is usually secret, and only passed to apprentices in their final level of training (at least in the past… the nationalization of the yixing industry changed this, and now… some yixing artists have returned to using secret blends, but how secret they are is questionable). In the past, many yixings we’re made from clay from single mine – blending was rare. Now nearly all yixing teapots are made with blended clay.
  • The clay is mixed and churned to the right consistency. Water is consistently skimmed off the top to continue removing floating impurities.
  • The clay is kneaded, hammered, and thrown into a block. It is now ready to be used for ceramics.


Remember: the clay is the single most important attribute to consider when purchasing a yixing teapot. You should be purchasing the yixing teapot for its positive affect on the flavor profile of a single type of tea – and the clay is responsible for 99% of that effect. The shape and size matter much less than the purity, quality, and firing of the clay.

Projects in Machine Learning and Artificial Intelligence on Tea

What could a machine possibly learn about tea? And why would any AI want to learn about tea? We can barely find any humans to study tea!

I taste therefore I am.

My company uses machine learning and narrow-band artificial intelligence to understand what people taste in complex food and beverage products – the AI we’re building probably won’t take over the word any time soon, but if it does, it’ll just make everything taste better.

So why AI?

AI is a bad term for a wide range of research and capabilities; our narrow-band AI can be better thought of as automated machine intelligence to identify and control for subjectivity in human sensory data. Our goal is to strip away the influences of age, sex, race, socio-economic status, past tasting experience, first language, and smoking habits from what people claim to taste in a product, and arrive at the underlying chemical composition of flavor active compounds – without any lab equipment.

Once we do that, the real fun and intrigue begins. For example, we use that data not only to build real-time quality control monitoring for flaws, taints, and contaminations in beer – but also to determine what percentage of the population will be able to taste any quality control problem and the overlap with the producer’s target customer demographics. In bourbon, we’ve developed flavor-profile optimization strategies in the production process, and have helped producers predict the optimal barrel and bottle aging, removing a lot of the guess work from the process.

What projects do I have in mind for tea?

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