Wood Fired Nixing

We are big fans of Huang Fu Sheng's work, especially his wood fired teapots (some of which we couldn't part with and have kept for ourselves). This spring we were fortunate enough to time our visit with the opening of the kiln. 

Wood Fired Kilns of Nixing

The site of Huang's kiln is a village with a history in Nixing ceramics and once the home to a number of wood fired kilns. Not far from Huang's studio is the ruin of an ancient mantou kiln.

While many have heard of the famous dragon kilns of China, the mantou kiln was often used for firing Nixing ceramics as well. The mantou kiln was named after its mantou or steamed bun-like shape. While dragon kilns could be used to fire a large number of pieces at once, mantou kilns were for smaller batches, but were a preferred kiln for more delicate and sophisticated pieces. 

Nixing wood fired kilns were common in Qinzhou and the surrounding area until the later half of the twentieth century. With the advent of gas and electric kilns, wood kilns, with their more labour and resource intensive requirements, were increasingly seen as impractical and obsolete. By the 1970s and 1980s gas and electric kilns replaced wood kilns in the industry. While gas and electric kilns still dominate the industry, there has been a recent rekindling of interest in the traditional wood firing process.

The kiln described below is the one used to fire our wood fired Nixing teapots and is one of only a few large wood kilns operating in Nixing today. Although recently built, the kiln carries on the tradition of the village where it was situated, and where the ruins of ancient kilns can be found.

The Process

The process of firing Nixing Teaware in the wood kiln takes time, labor and fuel. From placing the pieces in the kiln until the firing process is complete, it takes 4 days and 3 nights. Once the firing is complete it will take another 7-10 days for the kiln to fully cool down. The process is difficult, and only has a 60% success rate.

The firing process must proceed carefully to ensure the kiln reaches and sustains each stage of the firing process within desired temperature parameters.

1°C- 300°C

This stage takes 24 hours. As the temperature climbs, the remaining moisture evaporates from the clay.

300°C - 800°C

This stage will last over 10 hours. During this stage, the clay will finish shrinking and its shape will be finalized. 

800°C - 1000°C

This crucial step takes over 10 hours. The temperature has to rise slowly and evenly, otherwise defects could occur. This is also the part of the process when the atmospheric conditions may be controlled (by either firing under an oxidized or reduction environment).

1000°C - 1200°C

Once it reaches 1200°C, the kiln will remain at this temperature for 5-10 hours. At this stage, yaobian will occur and ash particles that have formed by firing the wood will settle on the surface of the clay to form partial glazing.

During firing, the potter will place a stone slab with two clay bars. One of the bars is white clay with a transparent glaze, the other is made of the same Nixing clay fired in the kiln. The white bar is checked to see if the glaze has vitrified – indicating the kiln as reached 1200°C. The other bar is to check the affect of firing clay uncovered in the kiln.

Testing slab after firing:

 

Kiln Atmosphere

Yaobian or the transformation of the color of the clay, in the case of Nixing its variable red or dark grey/black appearance, occurs between 1000°C - 1200°C. However, it is the atmosphere in the kiln, including the degree of oxidation occurring (whether it is a reduction firing or oxidation firing) at this stage, that determines the appearance of the yaobian.

The atmospheric influence also includes the exposure of the clay to ash particles and pine oil (also known as "kiln sweat"), floating by or dripping down, onto the teapots. While it is impossible to completely control what the outcome will be, it can be adjusted using knowledge and experience. The inner area of each shelf experiences a more stable temperature and less exposure to ash, whereas the outer sections are more likely to receive stronger coloration from exposure to ash and pine oil but also greater temperature fluctuation and therefore greater risk of damage. For pieces that are intended to have more striking coloration from ash and pine oil glazing, they will be placed in the outer sections.

Wood fired Nixing teapots with characteristically striking colours from yaobian, ash glaze and kiln sweat:

Wood fired pieces have a higher scrap rate than those fired in electric or gas kilns. The tea caddy below was damaged during firing: 

Affect on Tea

Despite having partial glazing in places from the ash, wood fired Nixing teaware tends to often have a more muting affect on tea than Nixing teaware that has been fired using gas or electric kilns. The difference between the two would seem to be similar to the difference between zhuni and the more muting affect of zini clay.