Museum Forge Update – Crossed Heart Forge

Traditional Japanese swordsmithing forges can be constructed with simple materials and natural ingredients. This article will present a photographic overview of the process of refurbishing the swordsmith’s forge at a museum on Vancouver Island.

Most of history was forged with very simple equipment made from found and natural materials. A basic charcoal forge can be made with clay, brick, or even mud and stone.

The forge was originally constructed in 2016 and was in need of some repair and adjustments for efficiency aimed at its current type of operation. The first goal was to repair the walls and tuyere using the few available firebricks and other materials on hand. The second was to reduce the charcoal bed and floor depth for smaller project work and to cut down on the amount charcoal fines needed to insulate it during use. The large scrap anvil was also replaced at a later date.

Raising the Forge Floor

The lower half of the entire forge was filled with charcoal fines (kona-zumi), filtered through a ~5mm screen but caught by a window screen to separate the dust out. The charcoal bed provides an insulated and adjustable floor depth for the forge area and is wet down before each lighting of the forge to prevent it burning up.

For the current use of this forge a deep fire is rarely required so the floor of the forge was filled in and raised to a layer closer to the normal operating depth. The existing charcoal bed was shoveled out, the brick walls rebuilt, and the floor filled with stones and rocks to about 2sun below the required depth.

The sidewall that takes the bulk of the heat (across from the tuyere) is protected with a reclaimed kiln shelf and the floor is raised and shaped with stones of various sizes.

Replacing the Higuchi

The tuyere side wall is constructed of hard kiln brick and a new higuchi (tuyere) is built from brasque fire clay (6:2 charcoal powder and clay). Some schools build the tuyere separately and allow to dry before installing (as in the original build) but in this case it was built in place and allowed to dry after installing (some schools don’t even wait for drying before lighting the forge!).

The higuchi protrudes about 1sun into the firepot and tapers the airflow from ~2sun down to 1sun just as it enters the fire.

Modifying the Forge Floor

The rough stone floor is filled with smaller stones as much as possible and then about 1sun of brasque fire clay (6:2 charcoal powder and clay) is used to provide a smooth surface for the charcoal bed to rest on. There is space for about 1sun of charcoal fines below the tuyere to protect the clay floor of the forge and allow for some depth adjustment.

The floor forms a curved depression from the front of the forge to the front of the charcoal shelf, and is centered below the higuchi.

After the tuyere has dried the charcoal fines are added to the floor and smoothed in preparation for lighting the forge (photo taken after the first firing).

View of the kiln shelf hot spot wall and charcoal bed after the first firing.

Brick Workshop Floor

Reclaimed bricks from the island forge project were used to finish the entire floor around the workshop area, providing a clean place for chopping charcoal and using the sen-dai.

Reclaimed brick flooring provides a clean workspace.

Clean space for sumi-kiri (chopping charcoal) and using the sen-dai staple vise.

Views of the Forge

Morning light in the forge as the day’s preparations begin.

View from behind the forge looking toward the anvil.

View from the back toward the front of the forge with tied bamboo and earthen wall detail.

Close up of the central working area with several tools within immediate reach of the smith.

Bladesmithing forge tidied and set for the next day’s work.

Embers dying in the forge after yaki-ire.

Charcoal smoke from a day’s work highlights rays of sunlight across the anvil.

Special thanks to Pierre Nadeau for generously providing the fuigo for this project, along with the blacksmith crew who assisted with moving brick and stone. Thanks specifically to Dave Kasprick for enthusiasm, encouragement, and sharing his shop space and to the Craig Heritage Museum for hosting the forge.