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Summary:
Surface gloss is an important paper property. The interest in gloss exists because of its profound impact on the quality of printed matter. The quality issues relate to both printed and unprinted substrate. High gloss is often regarded as good in a print since it increases the apparent dynamic range. The shadow tones in a print especially are seen as deeper than on a similar but less glossy print. Varnished magazines are examples of high-gloss prints. On less smooth substrates the gloss may result in a disturbing mist on top of the print that decreases the apparent dynamic range. These effects can often be seen in newsprint, for example. In a previous paper we have studied the characteristics of gloss on relatively raw paper surfaces. It is clear from the measurements that there are two classes of gloss originating from facets on the surface and fibers. The fibers close to the substrate surface have an orientation such that there are specular reflections 180 apart when the specimen is rotated. The small facets only reflect specularly in one orientation. The work reported here is using the same setup as in the previous paper with 0 /60 observation/illumination angles and 360 rotation in the plane of the surface. There are two additions, however. One difference is that we have increased the photometric resolution using HDRI technique. The image registration of the position has also been improved by more sophisticated tracking software. The results from this exercise on low grammage newsprint quality demonstrate that there is a gloss asymmetry in the orientation of the machine direction (MD). The average gloss in the reverse direction is considerably higher than in the MD direction itself.