| Boiling Point No. 22 - August 1990 |
The stove is made of high quality fired clay with 1cm thick refractory lining (rice-husk ash/clay mixture, 5:1 by volume) on the inside. The outside insulation between the stove body and the metal bucket is made with rice-husk ash/clay mixture (12:1 by volume). The top outside diameter is 30.5cm and the height is 25cm. The complete stove weighs approximately 10kg. The special design features include a conical rim and slanted pot rests that can accommodate various sizes of pots from 16-32cm in diameter and many sizes of woks (with a constant 1 cm air exhaust gap). The grate is also unique; it is 4cm thick and has 61, 1.2cm diameter, equally-distributed holes (the hole area totalling about 30% of the grate). The stove costs approximately US$5.0 to produce and will last two to three years in domestic use.
The production cost will be lower when it is produced in greater numbers.
History and Field Experience
The design is the result of what is believed to be the most exhaustive charcoal stove testing project ever undertaken. All designs of charcoal stoves available in Thailand were tested and the data were analysed to develop optimum design criteria for a single stove that could use a variety of pots and pans. The design was simplified to ease construction and lower the cost. A demonstration and promotion campaign was started early in 1984, and the users of the first 400 stoves were impressed with the new stoves.
By 1986, the stove was being manufactured by one capital-intensive factory, several traditional stove manufacturers and a number of village groups, and some 10,000 were in use. The stove is now subject to a nationwide marketing campaign which aims to have over one million in use within five years.
The stove body and grate are made from a clay/rice-husk ash mixture formed in moulds. After the preliminary moulding they are finished by hand, dried and fired. They are then put in a metal bucket with a protective insulation between the stove body and bucket. The stove is portable and new grates can easily be purchased and installed.
Use of the Stove
The charcoal is lit with kindling and after two to three minutes the charcoal bed is burning and the pot can be put in place. The insulating layer reduces heat loss and keeps the charcoal bed very hot. The chamber only needs to be partially refilled to maintain maximum output. Closing the air inlet door will reduce the burning rate considerably. Left-over charcoal can be retrieved at the end of cooking by putting it into a covered jar or a sand pit to extinguish it.