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edit this page Crack Reduction in Clay Stoves: Jigger Jolleying vs Hand Making by Hugh Allen I was particularly interested in the conclusions drawn by A. Koopmans in his article (see Boiling Point 31, 1993) about the durability of the liners made on a jigger jolley in Thailand, and the statement, 'The low durability of stoves made by jiggering appears to be common'. The article then goes on to mention CARE's experience in El Obeid, Sudan, where jiggered stoves cracked, while hand-made stoves did not. What the article failed to mention is that: - The liners made by hand-made methods in El Obeid were produced with entirely different clay bodies and fired to a different temperature to the liners which were jigger jolleyed. It is not surprising, therefore, that the results were different. CARE did succeed in making liners on a jigger jolley in El Obeid that did not crack in use, but decided not to proceed because the clay deposits were too small, too variable and too far from the town. Significantly, the potter who worked with CARE in E1 Obeid commissioned his own jigger jolley when CARE's machine was withdrawn, and continues to make stoves.
- Liners are made in Khartoum by three separate manufacturers, all using jigger jolleys. Their average life in use exceeds one year, and no other liner-making technology is, to my knowledge, currently in use in the city. From a production of 800 per week losses during firing are only 0.5%.
- Liners are made on jigger jolleys in Senegal, Togo, Kenya, and Uganda. I do not have data for Uganda, but the average life of liners in Senegal is between 18 months and two years; two years or more in Togo and, in Kenya, between a year and 18 months. This evidence indicates that jiggered stoves are not lacking in durability, and that they compare favourably with liners made using other methods.
 Jigger jolly - foot operated |
The better results for jiggered liners in Togo and Senegal may be due to the greater use of grog in these two countries. Basalt sand is used in Kenya instead of grog, but is a poor substitute.
I was surprised that so little weight was placed on the use of grog. The experience of AT International and CARE has shown that clay quality is crucial, but nearly all clays require modification to avoid cracking. Clays are improved most effectively by the use of grog in amounts of up to 30 per cent, while silica sand is more likely to bring problems, even in small amounts, when firing temperatures exceed 600°C. The preparation of grog is difficult however, and so has limited the willingness of liner-makers to us it. Boiling Point's co-editor, Pete Young, comments on Hugh Alien's article as follows agree with Hugh Allen that grog is better than quartz sand but the reasons are not clear and are not entirely the result of the volumetric changes associated with quartz. We feel that the choice between grog and sand i less important than the need to reduce shrinkage and consequent residential stress. This reduction can be achieved by either limiting the clay content or using a process that minimizes the particle alignment; hence our theory that jigger jolleying causes more cracking because i is likely to cause more particle alignment.
[top] [end]Contents: Boiling Point 34: Smoke Removal  . |
Smoke in the Kitchen - Any Stove Will Smoke if You Dont Use it Correctly - Acute Respiratory Infection, Conjunctivitis and Accidental Burns - Exposure to Air Pollution From Transitional Household Fuels In A South African Population - Smoke Removal in Kenya - Chinese Chimneys - Indoor Air Pollution in Rural Tigray - Removing Smoke from Nepali Kitchens - A Breath of Fresh Air for Smoky Houses - Vietnames Kitchens - Reducing Greenhouse Gas Emissions and Improving Environmental Degradation - Indian Governments Stove Programme in Question - Cooking energy Efficiency in Indonesia - Phillipines Ricehull Stove - Stoves for Cafes and Food Stalls - Fuel from Three Stages of Pyrolysis - An Electric Metad - Crack Reduction in Clay Stoves
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