Artistry of Tatami Bricks: Crafting Time-Honored Kilns

I am in the process of deconstructing a wood kiln that was given to me. I found that the fire box top was made of Tatami bricks that formed the dome like cover. Before this, I had no idea what Tatami bricks were. So I was able to ask the owners of the kiln and though their notes and some research I was able to learn more about how tatami bricks are used. During the deconstruction, I have come to learn that kilns and kiln building is an art form.

In the realm of ceramics and pottery, traditions often blend with innovation to give rise to remarkable techniques. One such innovation is the Japanese style use of Tatami bricks, which can hold an important place in the construction of wood-fired pottery kilns before the mass manufacturing of kiln bricks. These bricks can be created to make homemade kilns when fired out. These bricks are more than just building materials; they are an embodiment of craftsmanship, carefully designed to withstand the fierce heat of the kiln. In this blog post, we will delve into the world of Tatami bricks, exploring their composition, significance, and the recipes that bring them to life.

Tatami Bricks:

Tatami bricks are specially crafted high-temperature bricks that find their purpose in creating wood-fired pottery kilns. They boast unique properties that set them apart. These bricks are meticulously designed to expand in all directions, adapting to the intense thermal environment within the kiln. Their angled construction forms a dome, contributing to the kiln’s structural integrity and heat distribution. The result is an environment that nurtures the transformation of raw clay into exquisite ceramic art. Tatami bricks are created by being hand built or packed into molds and dried, then bisque fired to cone 1. Each brick can weigh up to 5 lbs. They were rolled out clay cones on tatami mats.

Barnard Leach, in his book A Potter’s Book. , on page 194, talks about the use of these cones and the use of tatami bricks:

“The building of domes with such hand-made cones, whether solid or hollow, is very simple because the work is done from the supporting walls towards the crown and a light support is required only for the final horizontal courses. Any curve can be readily followed by proper selection a of the slightly varying cones and by the use of more or less mortar. The latter must be used more freely than in normal brickwork, and the percentage of grog to fireclay should be very high.”

These tatami bricks were used on a fire box on the kiln Japanese potter Hamada Shōji and Bernard Leach created, after meeting in Japan and traveling back to St Ives in 1921. You may see that kiln which still survives to this day by clicking here.

Fredric Olsen in his book , The Kiln Book. on page 69, discusses tatami bricks being used to support the domes of earthenware tube kilns in Japan. The Tamba tube Kilns, all twenty-three, are now protected by the Japanese government as cultural properties. You may see what a tamba tube Kiln looks like by clicking here.



The Mix:Tatami Brick Clay Recipe

The magic of Tatami bricks lies in the balance of their ingredients. Here’s a glimpse into a Tatami brick clay recipes:

Alumina:43.37 g
Grog: 34.97 g
EPK: 10.97 g
Fire Clay: 26.39 g

Alumina: 21.13 g
Cypress Ball Clay: 35.48 g
Tile #6 Kaolin: 28.72 g
Grog: 56.66 g

This blend of alumina, grog, EPK, and fire clay is carefully mixed to create a clay mixture that can withstand the extreme heat of the kiln while maintaining its structural integrity.

Tatami Mortar Recipes

But Tatami bricks aren’t just bricks; they are held together by Tatami mortar, another critical element. The Tatami mortar acts as both adhesive and insulator, contributing to the kiln’s efficiency. Here’s a Tatami mortar recipe that enhances the kiln’s functionality:

Fireclay: 50 g
Fine Grog: 50 g

Fire box mortar

Fine Grog: 34.78%
Fire Clay: 34.78%
EPK: 17.39%
Portland Cement: 4.35%
Alumina: 8.69%

This mixture of fire clay and sand forms the mortar that binds the Tatami bricks, creating a cohesive and thermally insulated structure. The combination of these materials ensures that the kiln retains and radiates heat optimally.

I have a long way to go in deconstruction. However,at the time of this writing, I have everything down and stacked on pallets but the twenty-foot smoke stack. It is possible to make a total homemade kiln using the Tatami method of construction.

Sources:

  • Ceramics Monthly. June 2003, page 74.
  • Olsen, Frederick L., The kiln book: materials, specifications, and construction. 1983, Chilton Book Co. 2nd ed.
  • Leach, Bernard. A potter’s book. 1976, Faber in English – 3rd ed.
  • Personal knowledge and research.
  • See more Tatami bricks being used here: Rock walls, and tatami bricks
  • All images used were taken by me, the author.

The recipes and information provided are for educational purposes. When working with ceramics, it’s essential to conduct testing to ensure safety and desired results.

Have you worked with or made Tatami bricks before? Let me know!

Happy Potting!

Written By,

Al Wayman

Artist/Owner

Creek Road Pottery L.L.C.

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