Want to add texture to a brick wall? Consider using clinker brick. Clinker brick are brick that are overfired, either on purpose or by accident. They were most common when brick were coal-fired in stationary kilns. Because of uneven heat, improper stacking, or other human error, the brick closest to the fire often became fused, twisted or glazed. Clinkers have advantages and disadvantages. Because they're hard and dense, clinkers can be very durable. But this also means they're likely to have a low initial rate of absorption (IRA). Glazed clinkers especially tend to float on mortar because they don't absorb much water from it. Twisted or fused clinkers can be difficult to lay, and voids easily can occur in mortar joints. Also, joints usually must be wider than normal to keep the courses horizontal.