While handmade and machine-molded brick are formed in molds individually, extruded brick are essentially kiln-fired slices of a column of clay. Extruded brick are generally the least expensive to make, so they are generally less expensive to buy. It is impossible to duplicate the range and character of molded brick using extrusion, but extruded brick manufacturers use a variety of methods to create texture and color.
Most extruded brick fire to a red body color, but gray, brown and other face colors can be created using sands and coatings. Lighter body colors can be achieved using specialty clays and additives, which are more costly but yield more consistent ranges of lighter colors. These brick are known as "admix" (short for additive mixture), commonly referred to as "through-the-body' brick.