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Color and Appearance Committee Round Robins on High-Quality Surface Appearance

The problems involved in instrumental measurements of the appearance of high-quality surfaces are currently being tackled by ASTM Subcommittee E12.14 on Multi-Dimensional Characterization of Appearance, part of Committee E12 on Color and Appearance. According to Andrew Rutkiewic, chair of E12.14 and president of Product Technology Consultants Inc., the singular non-color attribute that surfaces such as automotive coatings and highly polished metals and ceramics share are their mirror-like reflective properties. This attribute is known as directness of image (DoI) since it is visually perceived as the fidelity of an image reflected by the surface or, in other words, how close an image is to a perfect mirror. “Directness of image is greatly valued by the consumer and easily discriminated visually, but difficult to achieve and, more important, to measure instrumentally,” says Rutkiewic.

Subcommittee E12.14 invites all interested stakeholders, especially anyone who is concerned with the characterization of other non-color attributes of surfaces, to join their current efforts in obtaining instrumental and visual data through a series of round-robin experiments. This data will then be used by the committee to develop ASTM standards for high correlation instruments.

In the two round-robin experiments conducted so far, DoI and specular gloss measurements were obtained from a series of high specular gloss black automobile specimens. These measurements were then correlated with quantitative visual measurements of the specimens. Two conclusions drawn from these experiments are: 1) specular gloss measurements do not discriminate variations in DoI; and 2) all of the electronic instruments that were commercially available at the time of the first round-robin correlated poorly with visual perception, especially at the high-quality end where the competition is greatest.

During the second round-robin experiment, newly introduced instrumentation confirmed the first conclusion drawn from the initial round-robin. The correlation with visual perception was improved, but was still less than desirable.

At this point, E12.14 is in a third round-robin with automotive specimens that are black, white, silver metallic and dark green metallic. Instrumental data is currently being obtained, while quantitative visual data will be obtained during a joint meeting between E12 and Committee D01 on Paint and Related Coatings, Materials and Applications in January 2005. At that point, correlation will be determined. The goals of the subcommittee are to share this data with industry and for the data to result in electronic instrumentation, which will provide effective guidance for product developers and quality management.

For further technical information, contact Andrew Rutkiewic, Product Technology Consultants Inc. (phone: 505/281-7820). Committee E12 will next meet May 17-19 at the National Institute of Standards and Technology, Gaithersburg, Md. For membership or meeting details, contact Kevin Shanahan, ASTM International (phone: 610/832-9737).//

Copyright 2004, ASTM International