The way in which a log is cut for Kioke makes significant differences in its function.
When a log is sawn into a board, the board that runs through the centre of the tree will show vertical grain. This is called "quarter sawn"(柾目 Masame).
Boards cut well away from the centreline display a much more curved grain like contour lines. This is called "Back sawn"(板目 Itame).
Quarter sawn (柾目) material has the property of releasing moisture, so it is suitable only for a limited period of use.
The back cut (板目) material is used for tubs intended for long-term use such as those in brewing and storage, and this of course applies to Miso Kioke.
Back sawn material is suitable for brewing.
Because of this, only back sawn material is used in Taru manufacture. On the other hand, there are both quarter sawn and back sawn Oke.
This Oke uses the back cut (板目) material and suitable for Miso or Shoyu brewing.
This Oke uses the quarter sawn (柾目) material, which may not be very suitable for Miso or Shoyu brewing.
Utilising the characteristic of the quarter sawn (柾目) material, Koji Buta is made with the quarter sawn (柾目) material.