An apparatus (10) and method for evaluating an effect of a surface presentation angle (A). The apparatus supports a plurality of samples (12) separated by support plates (18) between end plates (22) in a shish kebab arrangement. A groove (34) is formed on each side of each support plate for receiving an edge of each respective sample at a different angle relative to an axis of impingement (32). A clamping mechanism (20) holds the end plates, support plates and samples together in the fixed orientation exposing each sample surface at a different presentation angle, yet at the same distance from a process end effector (30). The sample impingement surfaces are exposed to the process, and the effect of the different surface presentation angles is determined from the samples. Process variables to counter the effects of surface presentation angle may be identified and controlled.