Matters of hearth

ONCE Upon a time, potters eked outa comfortable living by producingearthen wares. Today, not too manypeople use their products and theirmarket has shrunk considerably.Besides, they have to buy firewood atexorbitant rates, while, earlier theycollected the same from nearby forests.These two factors have made themthe most economically backwardcommunity in the country.

Traditional kilns in Orissa use 1.2 kgof firewood for sintering (blending amixture into a solid mass by heating)each kg of thin-section potterylike earthen pots and two to three kgfor making roof tiles. Sintering isconducted at a low temperature of600'C. Hence, the products are poor instrength and have a short life. Also, temperature gradient in traditional kilns isnot uniform with the result that 10 to 20per cent of pots are rejected after everyfiring. due to under-or over-heatingor breakage. Traditional kilns alsorelease a lot of smoke, thus polluting theenvironment. After firing, they are tomdown and reconstructed to enableunloading- of the sintered pottery andloading of unbaked pottery, thusincreasing labour costs.

In -an effort to counter theseproblems, the Bhubaneshwar-basedRegional Research Laboratory hasdeveloped a low cost pottery kiln named'Queen'. The 'Queen' kiln is bottle-shaped with the chimney at the placeof the mouth. It uses low-grade rawcoal to bake products like domesticearthen ware, handicrafts, roof tiles,floor tiles, etc.

The 'Queen', a permanent structuremade of red bricks, clay and sand,has been in operation in Orissa andWest Bengal for the past two years.The pottery is loaded and unloadedthrough a door, cutting down drastically on labour. The On design ensuresan uniform high temperature of800-900'c during baking, which reducesloss due to breakage and also increasesthe life and strength of the products.Firing time is also reduced in the'Queen', which takes a total of seven to12 hours depending on the moisturecontent of the pottery, while traditionalbiomass kilns take up to48 hours. For firingY one kg of pottery, 125-175 gm of F-grade coalis utilised thus saving60 per cent energy. Thepollution caused by thekiln is minimal as thecoal is totally burnt. Byswitching over fromkilns to traditional'Queen' kiln, the overallcost of production goesdown by 50 per cent.

Depending uponthe size, the construction costs of these kilnsrange from Rs 6,000to Rs 18,000 in ruralareas. The average lifeof the kilns is five to 10years depending on themaintenance.