Masonry oven India, tandoors are traditional clay ovens, although these days modern electrically fired tandoors are available. The open-topped tandoor is a transitional design between the earth oven and the Roman-plan masonry oven. In the precolumbian Americas, similar ovens were often made of clay or adobe and are now referred to by the Spanish term "horno" (meaning "oven"). Horns are also traditional in the American Southwest. The traditional direct-fired masonry design is often called a "Roman" or "black" oven and dates in Western culture to at least the Roman Republic. It is known as a black oven because the fire generates soot
Masonry oven bearing insulation and provides an easy way to break contact with surrounding cold. Some earthen oven builders use a lo-cost combination of empty glass bottles surrounded by an insulative mix of clay and fine organic matter (sawdust, chaff, nut shells, etc.); as the organics burn out, they leave thousands of tiny voids in the clay, making a spongey, insulative, and firm foam-like material. To keep the top of the oven warm, masons may build walls around the oven, crib-like, to make space for a loose cover of perlite, pumice, or vermiculite. For a smaller profile and a rounder look, the