Firing of Yixing Teapots
An Overview of Yixing Kilns
Each renowned historical ceramics center developed a unique combination of techniques, from clay processing to ware construction and firing, in order to achieve their sought-after qualities. Kiln design, fuel, and firing schedules were major areas of innovation[1], with some information held as closely guarded trade-secrets and other information easily available to experts in ceramic formulation and kiln construction throughout China[2].
This chapter focuses on kiln technology for the firing of zisha wares; the chapter takes a linear approach to the historical development of firing methods from wood firing in dragon kilns, to the development of downdraft kilns, and the contemporary use of electric kilns. In taking a developmental approach to the topic, with the exception of a brief review section on complete firings, I forgo independent technical sections discussing fuel, atmosphere, and kiln design and instead focus on the innovations and tradeoffs of kiln firing within their integrated historical contexts. This chapter is thus intended to be read sequentially, as historical and technical context are not re-explained in each subsequent section.
A kiln-site is a locality that has born a collection of kilns across time, where kilns have been built, rebuilt, repaired, redesigned, and restructured. A kiln-site does not connotate that a specific kiln within the site has remained in continuous use; an important context when a village kiln-site may have a discontinuous series of kilns built over the remains of older kilns, used to fire the developing wares local to the region over time. Often older kilns and newer kilns coexist within a single kiln-site. The firing of zisha clay wares in Yixing took place in countless kiln-sites[3] that had been in operation since the Qin (221 – 206 BCE) and Western Han (202 BCE - 9 CE) dynasties, with modern zisha becoming the primary ceramic product by the mid-to-late Ming dynasty (1368 – 1644 CE). The kilns of Yixing adopted new firing methods for the firing of zisha and other minor-ceramics of the region[4], including adjustments to the fuel source and firing schedules[5], adapting the leading kiln technology of each era to their needs. All early (pre-Ming) kiln-sites in Yixing were composed of communal kilns, shared and tended for by the village; private kilns, owned and operated in a capitalistic fashion, arriving in Yixing by the early 1600s CE at latest[6].
From the earliest zisha teapots (mid-Ming) to the beginning of the communist era, Yixing wares were fired in wood burning dragon kilns (龙窑, long yao), which were the predominate firing method in most major ceramic centers throughout China. Yixing, like many other ceramic centers, fired its wares in saggars[7] to prevent ash, natural glaze, and the “fire-touched” (惹火, rehuo) flaw from forming on the unglazed wares.
The foundation of Yixing Factory 1 (“F1”) in 1958 and the government’s focus on industrialization led to the experimentation and development of new methods for firing ceramics. The Yixing kilns went through a rapid period of experimentation starting in the 1960s with variations on downdraft kilns[8], a form of single-chamber kiln[9]; before developing the tunnel kilns[10] in 1965 which replaced all other active kiln-types by 1973.
Electric kilns were available for experimentation and production firings by the late-1980 or early 1990s, becoming viable for small scale firings around the end of the F1 era and the privatization of Yixing Factory 1. Today, many artisans have an electric kiln for experimental firings and developments, or for independent use in conjunction with a tunnel kiln.
This chapter thus covers the sustained use of the wood fired dragon kiln throughout the dynastic period for all historical zisha wares, the brief experimentation with coal-fired downdraft kilns and their reemergence as wood fired kilns in the contemporary era, the development of the now-standard tunnel kiln (switching from coal and oil to gas), and finally the arrival of electric kilns.
[1] In addition to kiln loading patterns to create even airflow and knowledge of placement for hotter and cooler areas within the kiln.
[2] As in other industries, there were two overlapping yet distinct sources of knowledge exchange within dynastic China: the literati wrote articles for the provincial gazetteers and stand-alone manuscripts for publication, sharing knowledge while promoting their views and expertise to other literate scholars and officials; separately, the (often illiterate) craftsmen and artisans embodied practical knowledge learned from trade; such knowledge was exchanged both via individuals changing jobs or immigrating to new areas, and through exchange with the Imperial Workshops in Jingdezhen (the Imperial Kiln) and within the Forbidden City (the Imperial Workshop), where craftsmen were temporarily hired before returning to private practice.
[3] Most dragon-kiln-sites in Yixing are identifiable by excavating the discard piles of broken teapots in close proximity; craftsmen controlled the quality of their available work by destroying pieces that didn’t meet their standards after firing, or those pieces which cracked during firing.
[4] Such as Yijun (宜均), and other daily use wares made of non-zisha clay.
[5] A firing schedule is the timeline of temperature and kiln atmosphere throughout the firing. A different firing schedule will yield a different time-temperature curve; the firing schedule can be modified by changing the amount of fuel, the fuel source, or the placement or removal of blocks in the mouth or ports for airflow (which will modify the kiln atmosphere and thus time-temperature curve of the firing).
[6] Coinciding with economic reforms leading the monetization of the Chinese economy in the late Ming dynasty.
[7] Saggars are ceramic boxes used to protect wares from the kilns’ atmospheric ash and flames, which can form surface deposits, natural glazing, or the fire-touched (惹火, rehuo; which is a form of yaobian, 窑变, “kiln changed”) flaw. Ash deposits, sporadic glaze, and rehuo flaws are rarely found on Yixing wares from the official kilns as (almost) all wares were fired in a saggar; ash deposits on a Yixing may be an indication of an antique private commission, or a contemporary wood firing.
[8] Both coal firing kilns (煤窑, mei yao) and oil firing kilns (重油窑, zhongyou yao).
[9] Contemporary wood fired Yixing teapots are most often fired in a wood burning downdraft kiln.
[10] Tunnel kilns were originally coal and oil fired at the time; with experimentation in design and process continuing throughout the F1 and into the present period. Modern tunnel kilns are gas kilns (气窑, qi yao), firing wares by burning natural gas.