An insight into the present capabilities of national metrology institutes for measuring sparkle

Abstract

Large effect pigments, due to their strongly specular reflectance, produce a special visual texture known as sparkle. The use of these pigments in many industries (automotive, cosmetic, paper, architecture...) makes the control of this visual texture necessary. A measurement scale has to be developed, so that traceability can be provided by national metrology institutes (NMI) or designated institutes. Some of them (PTB, METAS, CMI and CSIC) have tested their existing capabilities to measure sparkle, and their results are presented. Two possible sources of systematic errors have been identified: inadequate illumination and collection full-angles, and inadequate size of the virtual aperture used to assess the luminous flux reflected on the effect pigments. The measurement scale of sparkle used in this comparison is thoroughly presented. This comparison will allow the methodology to measure sparkle to be improved.