The top of the foundation should be just above ground level.
Figure 4.5 A cross section of the foundation
The fireboxes
1. Stand a straight stick upright in the centre of the foundation with a piece of string, (at least 85 cm
long) tied to the bottom of the stick. Tie a short, sharpened stick to the other end of the string, 75 cm
from the centre pole. Use the stick to mark a circle of 150 cm diameter on the foundation. This is the
inner diameter of the kiln.
Figure 4.6 Marking out
2.
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Mix a good building mortar. In west Kenya, we used the following mixture:
one portion of sand
two portions of murram
one portion of ant hill soil
enough water to make it a thick, sticky mixture.
• Soil making ratios will differ from region to region.
• If ant hill soil is not available, either good quality building earth or ash can be used.
• Do not use cement as it will crack in the heat.
3. Spread a thick layer (about 2 cm) of mortar on the foundation outside the 150 diameter circle you have
marked. Lay the mortar 5 cm beyond the width of the bricks to be used, laying the bricks as shown in Fig.
4.6, with mortar in each joint between bricks. Level each brick as it is laid until the circle is complete.
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