The Enigmatic Science of Japanese Climbing Kilns

Climbing kilns are made up of several connected firing chambers built up a hill, each positioned higher than the last. The first and lowest chamber is filled with extremely large quantities of firewood for fuel. Once the fires are lit, the heat and flames travel up the slope from one chamber to the next. Due to the way heat rises, the upper chambers are preheated by the firing in the lower chambers; they also recycle the heat from below. 

Furthermore, the arched shape of each firing chamber causes heat and flame to rise to the top of the arch, then fall again before being pulled up through the channels between chambers, up the slope, to continue the process in the next firing chamber. This circulation of fire and hot air within each chamber helps evenly heat the stacked ceramics. Many noborigama are a type of “downdraft kiln,” so called due to that pattern of falling air. Eventually the air travels all the way through the kiln and out a chimney or flue at the far end.

The firing chambers of Le Sanpei Kiln and Hozan Kiln’s noborigama have openings in the side for people to enter and place pieces to be fired. When it’s time to fire the kiln, these openings are sealed with bricks and clay. Even after the firing is over, the inside of the kiln stays hot for several days.

The way noborigama are loaded is another key to the quality of the ceramics they produce. The entire first chamber of the kiln contains fuel alone, no ceramics. The benefit of this is that when the first chamber is opened to add more fuel—necessary for the hours-long, high-heat firing—the temperature in the upper chambers doesn’t change that much. Temperature stability is crucial for glazed ceramics; meanwhile, unglazed pieces interact directly with the falling ash, resulting in their distinctive textures.

In wood-fired climbing kilns, falling ash can create mysterious, beautiful patterns. Bizen ware is famous for this. Wood ash drifting through the kiln melts and fuses to ceramics when heated to high temperatures, creating this effect. As you look at Bizen ware’s unglazed surfaces, you can see the patterns left by fire and ash, and imagine the dance of heat and flames that turned raw clay into completed masterpieces.

For those ceramics that the artisan doesn’t want to be coated with melted ash, potters can use a saggar box. Typically made of clay, and these boxes protect the items inside from falling wood ash. Le Sanpei Kiln uses saggar boxes for some of their pieces. What looks at first glance like a cylindrical support column to hold ceramics high up in the firing chamber is actually a stack of saggar boxes, each full of ceramics.

The fire of a noborigama has to be fed over the course of days, sometimes weeks for the largest climbing kilns. Kiln tenders typically add fuel to additional fireboxes located at the bottom of each successive firing chamber to make sure each chamber reaches the necessary temperature—which can reach as high as 1,300°C (2372°F) or more. This can be sweaty, difficult work, especially for the potters of the past, who worked long shifts in the grueling heat of the flames. The city of Tajimi in Gifu Prefecture, historically a pottery town, believes that meals of high-calorie eel and drinking parties between firings is what helped those historic potters get through the punishing labor.

Each element of a noborigama—the separate firebox, the ascending slope, the multiple firing chambers, and the arched shape of each chamber—increases thermal efficiency compared to earlier Japanese kilns, which is what made the noborigama groundbreaking technology when it was first introduced to Japan, probably from Korea, most likely in the early 17th century. It meant that climbing kilns could produce much larger quantities of ceramics than earlier varieties of kiln available in Japan, which was crucial as domestic ceramics production at the time was beginning to expand.

It requires a huge amount of skill and experience to tend a noborigama. The complexity of the flow of heat and flame, the adding of fuel, the constant monitoring during firing, and the placement of pieces within a kiln take a trained hand to understand and get right. But the end result is exquisite ceramics. Le Sanpei pieces are luminous, while works from Hozan Kiln have a more earthy and matte finish. Both are difficult or impossible to achieve in any other way.

Bring home a piece of living Japanese art history today with pieces from Le Sanpei Kiln and Hozan Kiln.

If you want to learn more about climbing kilns, check out our article on kiln unloading at Hozan Kiln, where we got a rare behind-the-scenes look inside their noborigama.

https://musubikiln.com/blogs/journal/crafting-with-earth-and-fire-an-exclusive-look-at-kiln-unloading

We also get an exclusive look at Le Sanpei Kiln’s history, process, and noborigama here.

Noborigama are so notable partly because of what came before and after in terms of kiln technology. Below is a quick introduction to other types of kiln.

The earliest pottery in Japan—and the world—was fired not in kilns, but in pits: basic holes in the ground, stacked with items made of clay, with combustion fuel piled over top. Pit-firing only reaches temperatures of approximately 538–649°C (1,000–1,200°F )—not very hot compared to more advanced firing technology. This results in porous, earthenware pots. To give you a visual, most modern terracotta flower pots are earthenware, as the pores allow water to seep out. Jomon period (14000–900 BC) pottery was created in pit firings.

Anagama kilns, literally “hole kilns” or “cave kilns” for their shape, were brought to Japan by Korean potters around the fifth century CE. Anagama, like climbing kilns, are built up a slope and lit from an opening at the bottom, but unlike climbing kilns they consist of only a single chamber. These cave-like kilns were originally built entirely or mostly underground and can reach temperatures of 1,100–1,250°C (2,012–2,282°F ).

The main downside of the anagama compared to the noborigama is that the firebox is not separated from the chamber where the clay pieces are placed. This means that the temperature is hard to control and keep consistent, and the look of the final pieces can vary widely depending on how the kiln is loaded—i.e., the number of items, their sizes, and their placement within the kiln.

Ogama, literally “large kilns,” introduced in the late fifteenth century, are the evolution of the underground or semi-underground anagama. Although similar to the anagama in shape, ogama are built entirely or mostly above ground. As a result, they can be built with higher ceilings, allowing for the firing of a larger number of pieces at a time. However, just like in the anagama, the firebox and firing chambers are not separate, leading to wide variability among finished pieces.

So next time you touch one of Le Sanpei Kiln’s shining porcelain bowls or Hozan Kiln’s wabi sabi teacups, think about how that piece went through a transformation in the over 1000°C flames of a noborigama. Isn’t it awe-inspiring that a process so intense can create something so beautiful?

To view every beautiful detail of the pieces featured in this article, click here.