Concrete, more than any other major construction material, lends itself to color- ease of design in color, ease of construction in color. The easiest way- as far as jobsite skills are involved- to achieve colored concrete work is to obtain ready mixed concrete that incorporates pigments to achieve the desired color. However, colored ready mixed concrete is not available from some producers due to the small demand for it, increased cost, and problems involved. Another means of achieving colored concrete surfaces is the use of a specially prepared dry shake. After the concrete slab has been cast and leveled, a mixture of cement, aggregates and coloring pigment is spread evenly over the surface. The result is a concrete surface colored to a depth of approximately one-eighth of an inch. As can be deduced from the description of this method, it is limited to use on concrete cast horizontally, such as slabwork and tilt-up panels. Color applied after the concrete has hardened is not as long-lasting as the plastic concrete methods. Oil paints, rubber-base paints and synthetic resin paints are available for use on concrete and they do offer a variety of colors. Ordinary oil paints are sometimes unsatisfactory on concrete because moisture in the slab causes it to saponify (turn to soap). Portland cement-base paints alleviate this problem but they perform poorly under abrasion and require thorough curing to avoid dusting. Paint should not be used on slabwork were appreciable traffic is to be experienced. Probably the most versatile means of achieving color is the use of exposed decorative aggregates. Terrazzo is the most common colored concrete. It is an exposed aggregate finish that has been ground to a smooth surface. Because this calls for special skill and tools, terrazzo is usually subcontracted to firms specializing in this work.