If you are attempting to choose the best refractory brick for any project, you must first identify the purpose of the brick. If the refractory brick is destined for heating or cooking, you may want to follow the general consensus and choose a medium-grade fire brick for the job. This will provide you with a refractory brick that not only heats up quickly, it will withstand many duty cycles of heating and cooling without breaking. This fire brick will also retain heat much longer than a common, red clay brick resulting in less wood being needed to provide heat.
The purpose of a refractory brick is to absorb and maintain heat from a fire. The fire, typically wood-fueled, can be used for cooking, heating or a combination of the two. If you are seeking a brick for a specific purpose, you may wish to purchase more than one type of brick for the job. Quality fire brick can cost twice as much or more than a red clay brick. You may want to do the basic construction with the less expensive brick and use the quality fire brick to line the fire box.
When searching for the best refractory brick, you should choose only those bricks with a smooth, flat side. Curved bricks will result in gaps in the fire box, which could cause cool spots and uneven cooking. If choosing bricks for the floor of an oven, the straight sides will fit snugly together, providing you with a smooth and even oven floor. The tight fit is also recommended since many builders do not use mortar between fire brick floors. The firebrick is simply placed in the oven tightly beside each other to form a nearly solid oven floor that pizza and bread can be easily slid on and off.
When searching for a quality refractory brick for a fireplace lining, you may want to choose medium- or heavy-duty fire bricks. The heavy-duty fire brick is made with more alumina, creating a brick that will not only reach a higher heat than a medium-duty fire brick, the brick will retain the heat for a much longer period of time. This provides additional and prolonged heat from the same amount of wood in a fireplace. While a medium-duty refractory brick is manufactured of roughly 38 percent alumina and 50 percent silica, the heavy-duty fire brick contains 50 percent or greater alumina.