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 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.
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!
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?
It has been known as late as the Ming Dynasty that tea was most suitably brewed in a Yixing teapot. The special Yixing clay helps to refine and round out flavor profile of fine Chinese tea, and can help you achieve the ultimate goal of GongFu – brewing good tea.
Yet finding, sourcing, and understanding Yixing can quickly become an expensive and sisyphean undertaking. The vast majority of “Yixing” wares available on the market are frauds, made out of industrial clay using slurry molds. Learning to identify real Yixing requires experience with known samples of known provenance and known age – that’s particularly difficult given that Qing and ROC yixing artists were faking Ming Dynasty pots with real high quality clay for generations. Determining the age or provenance of a teapot is difficult or impossible even for experts.
Should you find a Yixing you trust as real, the task continues to grow exponentially in complexity; not all Yixing pots are created equal, and there is in fact a wide range of sub-types of Yixing clay commonly used to make Yixing teapots – some of which should only be used for specific teas or under specific conditions.
At the Tea Institute (of which I am only an advisor) we have set out to analyze the chemical composition of the clay, the clay’s effect on the sensory attributes on various classes of teas, and the chemistry that causes these sensory changes. Eventually, this research will yield a better scientific understanding of the magic and allure of Yixing clay.
Namaste friends, romans, 茶人, & countrymen! It has been far too long, with far too little tea and tea related adventures since I last posted.
But the wait is over.
After this most successful event, the 2015 Yixing Teapot Exhibition, hosted by the Tea Institute at Penn State, I feel alive to the allure of tea once again.
Ryan Ahn (狮子) has done an unbelievable job of taking over the institute I founded and I am so happy to remain involved in an advisory role. Ryan and his executive team are 100x better at recruiting than I (and my executive team, sorry guys) ever was/were.
Under Ryan and the new executive board, the Institute has grown to 44 active members! (all of whom are directly descendent from my tea linage, making me far more proud than the parents of an honor roll student)