Abstract
Specular gloss is an important appearance property of a wide variety of manufactured goods. Depending upon the application, e.g. paints, paper, ceramics, etc. different instrument designs and measurement geometries are specified in standard test methods. For a given specular angle, these instrument designs can be broadly classified as converging beam (TAPPI method) and collimated beam (DIN method). In recent comparisons of specular gloss measurements using different glossmeters, very large standard deviations have been reported, well exceeding the manufacturers claims. In this paper, we investigate the effect of instrument beam geometry on gloss measurements. These results indicate that this difference in beam geometry can give the magnitude of gloss differences reported in these comparisons and highlights the importance of educating the user community of best measurement practices and obtaining appropriate traceability for their glossmeters.
Highlights
In a recent investigation of the inter-instrument agreement of specular glossmeters conducted as part of the European Metrology Research Programme (EMRP) project entitled “Multidimensional Reflectometry for Industry”, it was reported that the reproducibility between 6 different commercial glossmeters on 25 different painted gloss samples exceeded the threshold gloss unit (GU) values given in ASTM D523-14 for more than half of the comparison samples [1]
In the case of both the medium (GU53) and high gloss (GT53) coated paper samples measured at 75° geometry, the differences in the measured gloss values for the two different methods (6.3 –7.8 GU) were a factor of ~4 to 8 times larger than the measurement reproducibility for a given beam condition (0.7 -2.4 GU)
In the case of the medium gloss paper sample (RG01) measured at 20° geometry, the National Research Council of Canada (NRC) results showed a very large gloss difference of 23.4 GU in going from the converging (TAPPI) to the collimated (DIN) beam method compared with an excellent measurement reproducibility of 0.6-1.2 GU for a given beam condition
Summary
Investigation of converging and collimated beam instrument geometry on specular gloss measurements Zwinkels, Joanne C.; Côté, Éric; Morgan, John. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur. For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.
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