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ARS Home » Southeast Area » New Orleans, Louisiana » Southern Regional Research Center » Cotton Structure and Quality Research » Research » Publications at this Location » Publication #220775
Title: Investigations of the Impacts of Instrumental and Operational Variables on Color Measurements

Author
item Rodgers Iii, James
item Thibodeaux, Devron
item Cui, Xiaoliang
item MARTIN, VIKKI - COTTON INC
item WATSON, MIKE - COTTON INC

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/22/2007
Publication Date: 10/1/2007
Citation: Rodgers III, J.E., Thibodeaux, D.P., Cui, X., Martin, V., Watson, M. 2007. Investigations of the Impacts of Instrumental and Operational Variables on Color Measurements. World Cotton Research Conference-4. CD-ROM, #1605. . Meeting Proceedings.

Interpretive Summary: Color measurements for the classing of U.S. cottons have been performed on the Uster™ High Volume Instrumentation (HVI) instrument for several years. Two color parameters specific to cotton—Rd (reflectance) and +b (yellowness)—are used in the color measurement of cotton. Since Rd and +b do not readily relate to other well known and globally recognized color systems, a program was implemented to evaluate and validate the relationships of Rd and +b to a globally recognized color system (L*a*b*) and to investigate the impacts of key instrumental and operational variables on the color results. L* is how dark or light a material is; a* is how red or green a material is; and b* is how yellow or blue a material is. Tile and cotton samples were measured on 8 color spectrophotometers (bench-top and portable). Strong correlations were verified and validated on all color units. Thus, the use of L*a*b* for relating globally recognized color parameters from a color spectrophotometer to the HVI’s Rd and +b color parameters was validated. The primary variable that impacted the color agreement between units was the use of HVI glass in front of the sample. L* was the color parameter that was most impacted by the use of glass in the tile and cotton fiber color measurements. Distinct differences were observed between the different spectrophotometers for L* and L*'Rd correlation agreements when glass is used.

Technical Abstract: Color measurements for the classing of U.S. cottons have been performed on the Uster™ High Volume Instrumentation (HVI) instrument for several years. Two color parameters specific to cotton—Rd (reflectance) and +b (yellowness)—are used in the color measurement of cotton. Since Rd and +b do not readily relate to other well known and globally recognized color systems, a program was implemented to evaluate and validate the relationships of Rd and +b to a globally recognized color system (L*a*b*) and to investigate the impacts of key instrumental and operational variables on the color results. Tile and cotton samples were measured on 8 color spectrophotometers (bench-top and portable). Strong L*'Rd and b*'+b correlations were verified and validated on all color units. Thus, the use of L*a*b* for relating globally recognized color parameters from a color spectrophotometer to the HVI’s Rd and +b color parameters was validated. The primary variable that impacted the color agreement between units was the use of HVI glass in front of the sample. L* was the color parameter that was most impacted by the use of glass in the tile and cotton fiber color measurements. Distinct differences were observed between the different spectrophotometers for L* and L*'Rd correlation agreements when glass is used.