Technical Standard
Standardized procedure for measuring the specular gloss of paper at a 75 degree angle provides a consistent way to grade the shine of matte and semi-gloss substrates. Tappi t 480 is the primary reference used in North America for evaluating the surface appearance of coated board. It specifies the light source, the detector sensitivity, the lens aperture and the calibration tiles.
Geometry Rationale
The 75 degree angle is specifically chosen because it is highly sensitive to the surface variations found in paper products. At this shallow angle, the instrument can detect subtle differences in the smoothness of the coating that a 60 degree meter might miss. This precision is necessary for maintaining consistency across different production lots of a single grade.
By controlling the aperture and the light path, the method minimizes the impact of internal light scatter from the paper fibers.
Market Integration
Buyers and sellers use these values to define the gloss or matte categories in their sales contracts. A mill will guarantee a certain range to ensure the paper meets the customer’s expectations for a specific print job. Adherence to this standard eliminates the subjectivity of visual inspection and provides a hard number for quality control.
