Masoning a woodstove out of bricks

Today we started bricklaying for the wood stove in the workshop of Hans Baarslag and his colleagues Johan and Zuhair. On a frame, welded out of steel tubes, four concrete pavement tiles (size 60 cm x 40 cm) are placed. Five layers of bricks form a wall. On the inside horizontal channels will guide the hot air from the actual fire hearth to the outside of the wall.
Metal sheet panels placed outside this wall further guide the smoke to the chimney, while transferring its heat to the workshop. The picture shows the way in which the roofs of the channels are made out of two bricks resting against each other.
We used mortar made out of 1 part dry sand mixed with 1 part powdered clay. When dry, this is easy to mix, then water is added. We will experiment with a mixture of 1 part powdered clay with two parts dry sand. A 1 to 1 mixture is rather soft and limits the number of layers that can be laid to three to prevent sagging.