A note before we begin: I am not a ceramics historian. I am a first-time kiln builder, reconstructing a wood kiln donated by two master potters on Mother’s Day 2023. What follows is what I have learned by going back to the original source, the actual book by the actual man whose name is on the firebox design in front of Ana’s arch. What I found surprised me.
The Man Behind the Name
Most potters who fire a Bourry box kiln have never read a word Emile Bourry wrote. Neither had I. The name is attached to the firebox design the way Jacuzzi is attached to a hot tub, nobody thinks about the inventor anymore, they just know what the thing does.
But Bourry was real. He was a French ceramic engineer who published his treatise first in French and then, in a revised English translation by Alfred B. Searle, in 1901 and again in revised form in 1911. The preface to that second English edition describes his work as “long recognized as a standard work by the practical potter, who finds that the exhaustive researches of Seger demand more time for study than he can devote to such matters” (Searle v). The book was intended as a manual for working people rather than scientists — covering every class of ceramics from common brick to fine porcelain, written with, as Searle put it, “good classification and concise method of statement” (Searle v).
The firebox design that carries Bourry’s name appears in his chapter on fire-boxes, illustrated as Figure 132. Here is what he wrote about it, directly from the 1911 text:
“These are piled in the upper opening of the fireplace and rest on two brickwork projections. The combustion takes place by the air passing between the logs, the flames following the direction shown by the arrows. The embers which fall to the bottom of the fireplace help the burning, owing to the air entering through the ashpit door. This type of fireplace is built into the kilns; it gives very long flames and is suitable for all kinds of work.” (Bourry 195)
Two brickwork projections. Wood resting on them. Air passing between the logs from above. Embers falling to the ashpit below, supercharged by air entering from the ashpit door. Long flames. Suitable for all kinds of work.
That is Ana’s firebox. Built in 1999 by Matt Povse and Nan Burti. Reconstructed at Creek Road Pottery in 2024 by someone who had never built a kiln before. But described, with three figures and precise language, by Emile Bourry more than a century ago.
Why the Fire Burns Upside Down
The Bourry box is counterintuitive. In a conventional firebox, you light the fire at the bottom and the flame rises. In a Bourry box, you load wood into the upper opening where it rests on the hobs — those two brickwork projections Bourry described, and the fire effectively burns downward. Air enters from above, passes through the wood, and combustion gases follow the flame downward toward an opening at the base of the firebox that leads into the ware chamber.
The ember bed that accumulates on the hearth below the hobs is not waste. It is not an inconvenience to be managed. It is, according to Bourry, an active participant in the combustion, supercharged by the air entering through the ashpit door, generating radiant heat upward into the base of the fresh fuel sitting on the hobs (Bourry 195).
Modern combustion science has given us language for what Bourry observed empirically. In his chapter on wood and combustion, Jack Troy breaks this into two stages: volatile gas combustion, the resins, saps, and hydrocarbons released from heating wood, accounts for approximately 40% of total heat value. The ember bed combustion, non-volatile carbon burning in the presence of air, accounts for roughly 50% (Troy 37). Those two combustion zones, operating simultaneously and feeding each other, are what makes the Bourry box efficient in a way that a conventional grate firebox is not. The fire burns upside down because that arrangement separates the two combustion stages. A conventional grate firebox mixes them. The Bourry box refines them.
The Ceramic Arts Network glossary defines the Bourry box precisely as a “type of wood-kiln firebox where primary air enters at top of firebox, passes down through wood, and combustion occurs at level of grates or hobs, and is supercharged by the heat of the coal bed” (“Bourry Box”). That is Bourry’s Fig. 132 in nine words.
From Bourry to Ana’s Firebox: 115 Years
Between Bourry’s 1911 sketch and Ana’s reconstruction in 2024, the design traveled a specific route. Michael Cardew, the English master potter who studied under Bernard Leach, rediscovered Bourry box principles and built kilns based on them at Wenford Bridge Pottery in England (Troy 66). Gary and Daphne Hatcher at Pine Mills Pottery in Mineola, Texas, built their “Wanda Kay” kiln after Ray Finch’s rectangular kiln at Winchcombe Pottery, which Cardew had influenced (Troy 66). Karen Karnes built a Bourry box kiln in Vermont using plans from Ray Finch (Karnes, Studio Potter). Robert Sanderson and Coll Minogue built a single-chamber sprung-arch Bourry box in Creiff, Scotland in 1985 and fired it nearly 100 times (Troy 45). Will Ruggles and Douglass Rankin built kilns at Rock Creek Pottery (Troy 43). Jack Troy documented all of them in Wood-Fired Stoneware and Porcelain, published by Chilton in 1995. Matt Povse and Nan Burti built Ana in 1999, drawing on that lineage. She was deconstructed, moved, and donated to Creek Road Pottery in Laceyville, Pennsylvania, from Mother’s Day 2023 to October 2024.
What Ana’s Firebox Actually Is
Ana’s active combustion zone above the grate bars measures approximately 20.74 cubic feet. The full firebox enclosure is 32 inches wide, 56 inches deep, and 63.5 inches tall, 65.85 cubic feet total. Seven removable grate bars span the 32-inch width with 2.25-inch gaps between them. Three hobs serve as wood-rest points across the firebox width, left, center, and right.
That much is a well-executed Bourry box, consistent with the design principles Gary Hatcher summarized in his article “Chariot of Fire: Principles of a Bourry Box Kiln” (Pine Mills Pottery): six basic relationships govern single-chamber Bourry box performance — primary air inlet, firebox size, passages from firebox to ware chamber, ware chamber size, exit flue from ware chamber, and chimney stack height. What is not standard is Ana’s air system.
Ana has twelve draft ports arranged in four rows at staged heights across the firebox face:
Two rows below the hobs in the ash pit — three ports each at lower and upper ash pit levels. These manage primary air to the ember bed. As ash accumulates during a 26-hour firing, the lower-row ports become progressively buried; the upper row takes over. The stoker can read which ports are clear as a direct ember bed depth gauge. This staged system is the practical realization of what Bourry described in his Fig. 140 — his own firebox design: “most of the air required enters through a series of vertical openings placed on the hearth” (Bourry 240).
Two rows above the hobs in the active combustion zone — three ports each at approximately 9 inches and 18 inches above hob level. These manage secondary air to the burning fuel and to the gases rising toward the throat arch.
The uppermost row sits approximately 5.75 inches below the tatami brick roof. At that position, it injects oxygen into the gas stream at the last moment before those gases exit through the throat arch into the ware chamber. In combustion engineering, this is called overfire air. Introducing it, or withholding it, determines whether the gases entering the ware chamber are fully oxidizing or fuel-rich and reducing. This is pre-damper atmosphere control, managing reduction at its source rather than by restricting the exhaust through the chimney damper.
As Christy Wetzig documents from her own Bourry box firing practice, the critical challenge in operating any Bourry box is “maintaining a proper level of coals on the floor of the firebox. Let it burn too low and the fire on the hobs gets sluggish. Let too much wood fall onto the ember pile and the arch between the firebox and the ware chamber (aka ‘throat arch’) gets clogged with embers” (Wetzig). Ana’s staged ash pit ports address this directly, they are a continuous ember bed depth monitoring system built into the firebox face.
The Second Life: A Gas Kiln Inside a Wood Kiln
Ana’s firebox has a second operating mode. When we fire it as a wood kiln, the grate bars are in place, the ware chamber is open, and the full Bourry box system operates as designed. When we want to fire it as a standalone updraft gas kiln, we remove the seven grate bars, plug those openings with Kaowool ceramic fiber, seal the ware chamber throat with removable brick and Kaowool, and use the twelve staged draft ports as the primary combustion air system for the full 65.85 cubic foot enclosure. A 14-inch diameter exhaust flue cast into the tatami brick roof handles exhaust.
The Olympic Updraft 2831G kiln, used as a flue-to-volume ratio reference for calculating the 14-inch exhaust specification, has a documented flue-to-chamber-volume ratio of 1 square inch per 784 cubic inches of chamber volume. Applied to Ana’s 65.85 cubic foot gas mode volume, the calculation yields a required flue area of approximately 145 square inches, confirming the 14-inch diameter specification.
The refractory mortar science behind the arch that makes this dual-purpose use possible is supported by Norsker’s Self-Reliant Potter: Refractories and Kilns, which states that “mortars should resemble the bricks they join so that the joints and the bricks expand and shrink at the same rate during a firing cycle” (Norsker 57). Ana’s arch uses Empire S High Duty bricks (36% alumina) and Clipper DP Super Duty bricks (42% alumina). The mortar, fire clay and pool filter sand, is compositionally consistent with both brick types. Ana’s prior successful firing history at this specification confirms the mortar’s adequacy in practice.
What Bourry Would Recognize
If Emile Bourry could see Ana’s firebox, he would recognize Figure 132 immediately. The two brickwork projections. The upper opening where the wood goes in. The ashpit door below. The long flames passing through the throat arch into the ware chamber. He would also see that someone had taken Figure 140 — his own firebox design with its series of vertical openings, and built it out fully in a way his 1911 drawings only gestured toward. Whether the four-row air system performs as intended, whether the dual-purpose gas configuration fires successfully, whether a first-time kiln builder has successfully reconstructed what two master potters built in 1999 — all of that is still unknown. The arch is being mortared. The tatami bricks are being cast. The chimney waits. But the design lineage from a French engineer’s treatise to a kiln being rebuilt in Laceyville, Pennsylvania, is real and traceable. Ana is not a recreation. She is a continuation. The fire burns upside down, and it has burned that way for a very long time.
Works Cited
Bourry, Emile. A Treatise on Ceramic Industries: A Complete Manual for Pottery, Tile, and Brick Manufacturers. Translated and revised by Alfred B. Searle, Scott, Greenwood & Son, 1911. Internet Archive, archive.org/details/treatiseoncerami00bouriala.
“Bourry Box.” Ceramic Arts Network Glossary, Ceramic Arts Network, ceramicartsnetwork.org/Resources/Glossary/glossary-term/bourry-box. Accessed 7 July 2026.
Hatcher, Gary. “Chariot of Fire: Principles of a Bourry Box Kiln.” Pine Mills Pottery, pinemills.com/Articles/chariotoffire.html. Accessed 7 July 2026.
Karnes, Karen. “A Bourry Box Kiln.” Studio Potter, studiopotter.org/bourry-box-kiln-karen-karnes. Accessed 7 July 2026.
Norsker, Henrik. The Self-Reliant Potter: Refractories and Kilns. Deutsches Zentrum für Entwicklungstechnologien — GATE, 1987.
Searle, Alfred B. “Translator and Reviser’s Preface.” A Treatise on Ceramic Industries, by Emile Bourry, Scott, Greenwood & Son, 1911, pp. v–vi.
Troy, Jack. Wood-Fired Stoneware and Porcelain. Chilton Book Company, 1995.
Wetzig, Christy. “Firing the Bourry Box Kiln.” Christy Wetzig Ceramics, 4 Dec. 2017, christywetzig.com/2017/12/04/firing-the-bourry-box-kiln/. Accessed 7 July 2026.
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