Latest Wave of Gonioapparent Colorants Illuminated in New Standard
First generation gonioapparent colorants are materials pigmented with metal flakes that change lightness as illumination angles change. Used heavily in automotive coatings, the first generation of gonioapparent materials was covered by ASTM International standard E2194, Practice for Multiangle Color Measurement of Metal Flake Pigmented Materials, first published in 2003. Now, a second generation of gonioapparent colorants that change color with varying illumination and viewing angles has led to the development of a new standard, E2539, Practice for Multiangle Color Measurement of Interference Pigments. Both E2194 and E2539 are under the jurisdiction of Subcommittee E12.12 on Gonioapparent Color, part of ASTM International Committee E12 on Color and Appearance.
“Since E2194 was published, second-generation gonioapparent colorants have emerged,” says Jack Ladson, president, Color Science Consultancy Inc. “These more exotic gonioapparent colorants require different geometries than those specified in E2194 to characterize their optical performance. Hence the development path for E2539.”
In addition to use in the automotive industry, gonioapparent colorants are used for coatings, cosmetics, inks, packaging, paints, plastics, printing and security, as well as in architecture. Gonioapparent material is also now embedded in United States currency to prevent and deter forgery.
Ladson says that all interested parties are welcome to join in work on future revisions to E2539, as well as work on proposed new standards. “This is a dynamic field and new colorants with new characterization requirements continue to be generated,” says Ladson. “New standards are also needed for use of these colorants in specific materials, for example plastics and paint.” Ladson notes that the subcommittee is specifically seeking manufacturers and users of second-generation gonioapparent colorants who are interested in characterizing the optical effects of the colorants as used in materials specific to their interests.
Technical Information: Jack Ladson, Color Science Consultancy Inc., Yardley, Pa.
Phone: 215-369-5005 • E-mail:
ASTM Staff: Thomas O’Toole