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< prev - next > Energy Stoves and Ovens upesi_stove (Printable PDF)
Chapter Nine
Q The stove liner crumbles when I try to remove it from the mould. What should I do?
A The clay mixture could be too dry. Try adding more water, and give it time to soak evenly into the clay.
Probably you do not have good pottery clay. Have you tried the tests, i.e. making a thumb pot, or
making a sausage and coiling it into a circle?
If the same clay you are using is used by potters to make pots, then check whether you are collecting
the same type of clay (e.g. from the same depth) and preparing it in the correct way. You could try
resting the clay for a longer time.
If these do not work, then you may have added too much sand. Try reducing the amount of sand. If
this still does not work, then what you are using contains too little clay and is not suitable. Try to find
a better source of clay.
Q The stove loses its shape when I turn it out of the mould. Why?
A It sounds as if your clay is too wet. You should work with clay that is as dry as possible. Use a minimal
amount of water as you we moulding.
Q Why won't my liner mould smoothly?
A Make sure that the paddle blade is clean and smooth before you start moulding.
You may have lumps, stones, or other large particles in the clay. These need to be sorted and removed
from the clay mixture before moulding. If the clay appears to swell as the paddle moves over it, and a
lump appears behind the paddle, you have air trapped in the clay. You should remove the clay around
that area and replace it. Be careful not to trap more air.
Q My liners crack during drying. Why?
A There are several possible reasons for this problem. Maybe you are drying your stoves too fast. Try
slowing the drying process by covering the stoves for the first week with sacking or even polythene. In
the case of polythene, make small holes to allow the condensed water to escape. You can also make
the atmosphere in your storage space cooler and more moist. For example, if you are storing the stoves
in a metal-roofed room, try putting matting under the metal roof to keep the room cooler. Or if your
area is very dry, hang a polythene sheet or a wet sack over the doorway to your store, or sprinkle water
on the floor. Make sure that there is no draught.
It is also possible that your clay has very high shrinkage. Try doing the shrinkage test (see Chapter 2).
If this is the case, you can reduce the shrinkage by adding more sand to the mixture.
Finally, it is possible that your clay has not "rested" sufficiently. Try resting your clay for a longer
period. This could take several months, so you need to plan ahead and collect, prepare and store clay
while you use what you had previously prepared. Make sure that the clay does not dry out during
resting. The clay must remain moist. The resting enables the water to distribute evenly through the
Repairing cracks is not recommended, as this is difficult to do properly and the cracks usually
reappear during the firing.