Form S71 is a black and white spray strip. The left side is black and right side is white with overall dimensions of 2 x 11 in (51 x 279 mm).
These charts are used primarily by the automotive industry, including refinish operations, when evaluating hiding power of sprayed coatings. Typically the chart is attached to a steel or aluminum panel and the test coating is sprayed to produce a “wedge” varying from thin at one end and thick at the other. After drying, a location on the chart having adequate visual hiding (typically a Contrast Ratio of 0.98) is determined and the film thickness of the coating is measured on the metal panel adjacent to that location is measured. Conversely, a location of specified thickness is determined on the metal panel and the Contrast Ratio is measured adjacent to that location.