This standard specifies "Specular gloss of paper and paperboard at 75 degrees"

The TAPPI T 480 is for measuring the specular gloss of paper at 75° (15° from the plane of the paper). Although its chief application is to coated papers, it is also used for a variety of uncoated papers. This method is suitable for low- to high-gloss papers. For very high-gloss papers such as cast-coated, lacquered, highly varnished or waxed papers, and high-gloss ink films, TAPPI T 653 “Specular Gloss of Paper and Paperboard at 20 Degrees” is preferred.

It should be known that the very specific measurement geometry defined by the T 480 standard is very well defined and is not limited only to the angles but also to a number of other parameters critical for the correctness of the measurements.

The diagram below is quoted for a general explanation of the specificity of the measurement and to understand the impossibility of replacing this method with another measurement device.

T 480 has been shown to be suitable for gloss measurements of most ink films on paper or paperboard. Differences in the color and diffuse reflectances of these ink films have a negligible effect on measured gloss. For example, when white and black surfaces which are otherwise identical are tested, the white surface will measure less than one gloss unit higher than the black. This method does not measure image-reflecting quality.

GU Gloss units

• The theoretical specular-gloss standard is ideal, completely reflecting, a plane mirror having an assigned value of 384.4 gloss units.
• A flat, clean, and highly polished surface of black glass to measure 100 gloss units on this scale.

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