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Marine Analysis Program

Blotter Spot

The measurement of the merit of dispersancy of in-service engine oils according to Blotter Spot Method ASTM D7899. A drop of oil is deposited on a piece of specific filter paper and then placed in an oven set at 80 °C for one hour. The oil wicks across the paper and the oil spot is then illuminated with a constant and homogenous LED (light emitting diodes) backlight. A CCD (charge-coupled device) camera positioned on the other side of the paper takes a picture of the spot in black and white mode. The software analyzes each pixel of the picture. Dispersancy characteristics of the oil are judged by how far the oil drop spreads, how large the central sooty area is, and how homogeneous the opacity of the spot is in comparison with a theoretical reference diameter of 32 mm.