Architects specify colored mortar to enliven or differentiate masonry buildings for only a modest increase in cost. Colored mortar may be chosen to match, complement, or contrast with the masonry units. Because inconsistencies or flaws in joint color can ruin the look of the finished masonry wall, good quality control practices are essential. Controlling Materials All of the materials used to produce mortar can affect its color and should be controlled. Most pigments used to color mortar today consist of blends of red, yellow, or black iron oxides, which meet the requirements of ASTM C 979 (Pigments for Integrally Colored Mortar/Concrete). Pigments are available in either powder or liquid form. Accurate pigment measurement is essential for consistent mortar color. Avoid changing brands of cement or hydrated lime during a project. Similarly, all sand used on a job should be from the same source. The amount of water added to the mix also influences mortar color. Mortars having higher water-cement ratios tend to be lighter in color than those having lower water contents. Variations in the initial rate of absorption (IRA) of clay brick masonry also can affect mortar color. Workmanship is Critical Always important, good workmanship is even more critical on walls with colored mortar joints. Joint tooling greatly affects mortar color by drawing the pigmented cement paste to the surface, while pushing the sand down. Consequently, all joints must be tooled the same way. Clean With Caution Nine times out of 10, colored mortar problems result from improper cleaning. To prevent the cement paste from being washed away, allow walls to cure sufficiently before cleaning. Avoid using acid cleaners when possible. Be sure to test the cleaner on a small trial area of the building.