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United States Department of Agriculture

Agricultural Research Service

Title: Updating Hvi Color Measurements

Authors
item Rodgers, James
item Thibodeaux, Devron

Submitted to: Fiber Selection Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 13, 2006
Publication Date: June 6, 2006
Citation: Rodgers Iii, J.E., Thibodeaux, D.P. 2006. Updating hvi color measurements. Fiber Selection Conference Proceedings. CD-ROM. p. 50.

Interpretive Summary: The "grading" of U.S. cotton has been based on the Uster High Volume Instrument (HVI) for several years. A key quality measurement of the HVI unit is cotton color. Using a camera-based system and two broad-band filters, the older quality parameters of Rd (diffuse reflectance) and +b (yellowness) are obtained on the current HVI. The standards used for the HVI units are AMS reference cottons, which are not scientifically recognized standards such as those from NIST (National Institute of Standards and Technology). Two areas of significant opportunities and challenges for updating and improving the rapid and precise measurement of cotton color are 1)a better understanding and application of the present color system (Rd - +b) to well-known color systems (e.g., L*a*b*) and 2)the development of verifiable or "traceable" cotton color standards from AMS. In that light, new procedures and color systems are being investigated to update and improve the present color measurements and AMS color standards protocols. A program was implemented to study the relationship between HVI Rd +b and L*a*b*, to determine "standard" L*a*b* values for AMS standards, to determine the feasibility of verifiable AMS color standards, and to determine the primary sources of variability for the AMS standards. Initial results on one full range color spectrophotometer yielded very good correlations between the standard L*a*b* color parameters and the HVI's color parameters (L*'Rd, b*'+b). L* is normally higher than Rd, while very good agreement is often observed between b* and +b. These encouraging initial results offer great promise and potential for traceable HVI color measurements to a laboratory spectrophotometer The sample measurement protocols have been extended to eight different color units (portables and bench-top).

Technical Abstract: The "grading" of U.S. cotton has been based on the Uster High Volume Instrument (HVI) for several years. A key quality measurement of the HVI unit is cotton color. Using a camera-based system and two broad-band filters (two "wavelengths"), the older quality parameters of Rd (diffuse reflectance) and +b (yellowness) are obtained with the current HVI units. The standards used for the HVI units are AMS reference cottons, not on scientifically recognized standards such as those from NIST (National Institute of Standards and Technology). The color of the ceramic and cotton batts standards are measured on a master colorimeter-HVI by AMS. Two areas of significant opportunities and challenges for updating and improving the rapid and precise measurement of cotton color are 1)a better understanding and application of the present color system (Rd - +b) to well-known color systems (e.g., L*a*b*) and 2)the development of verifiable or "traceable" cotton color standards from AMS. In that light, new procedures and color systems are being investigated to update and improve the present color measurements and AMS color standards protocols. A multi-team program was implemented to study the relationship between HVI Rd +b and L*a*b*, to determine "standard" L*a*b* values for AMS standards, to determine the feasibility of verifiable AMS color standards, and to determine the primary physical/procedural sources of variability for the AMS standards. Initial results on one full range color spectrophotometer yielded very good correlations between the standard CIE color parameters and the HVI master colorimeter's color parameters (L*'Rd, b*'+b). Not unexpectedly, L* is normally higher than Rd, while very good agreement is often observed between b* and +b. These encouraging initial results offer great promise and potential for traceable HVI color measurements to a laboratory spectrophotometer calibrated to the CIELAB color system with a NIST-traceable standard. The sample measurement protocols have been extended to eight different color units (portables and bench-top) from four color instrumentation vendors.

Last Modified: 7/30/2014
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