Masonry oven more common as accessory features of a masonry heater. A compromise design known as the gueulard in France combines aspects of both internal and external-fired models. Masonry ovens remain popular in part because of the way their use affects cooking processes and food flavor. Where modern gas or electric ovens cook food by moving hot air around inside an insulated, lightweight box, a masonry oven works by soaking up heat, like a battery building up a full charge. When hot, the heavy oven walls release the heat slowly, for hours. Thus the food is cooked not only by hot air,
Kenya Ceramic Jiko remain slightly porous when temperatures reach 1150 °C; the clay should not warp or change shape when fired at 1250 °C. When the clay is fired up, it should turn to a light pink to white colour, and, to reduce the likelihood of cracking, it should shrink less than 8% after being fired. Clay which meets all the above standards is generally referred to as a "fireclay". To produce the Kenya Ceramic Jiko, two types of skilled labour are needed, a metalworker, and a clay worker. Other than a hammer, all other tools needed to manufacture the Kenya Ceramic Jiko