September 2000 Volume 22 Number 3

The Identification of Organic Pigments in Colored Pencils

A National Center for Preservation Technology and Training Grant to the American Society for Testing and Materials' Subcommittee on Artists' Paints and Related Materials (ASTM D01.57), with shared support from the Kress Foundation, has resulted in a large file of new information about organic pigments used in artists' coloring materials.

During 1998-1999, James Martin, of Orion Analytical Laboratory in Williamstown, MA, analyzed some 300 samples of colored pencils supplied to him by ASTM D01.57. The subcommittee had been working for nearly 6 years on a labeling and performance standard for these widely used materials, but had reached an impasse with the manufacturers regarding the identification of the pigment content of the pencils.

All other ASTM specifications for artists' materials require pigment content disclosure directly on the product label or in accompanying literature, but the colored pencil manufacturers were resistant to this kind of disclosure. It was hoped that the NCPTT/Kress-supported research would show them that it was possible to separate organic coloring materials from the other ingredients in these complexly formulated products and identify them. This would, D01.57 speculated, encourage the manufacturers to go along with the subcommittee's desire to have the new colored pencil standard conform to the format of the other standards. The colored pencil manufacturers finally agreed to the grant program application when the test method was re-written to blind the colored pencil samples so that company names would not be revealed.

The research produced a lengthy report and a library of CDs containing about 1000 pages of spectral curves, identifying approximately 98% of the organic pigment content in the pencil samples. In the written report, the pigments are identified using Colour Index Names, and by general chemical composition. In addition, Martin was able to identify much of the other organic content of the binders used in the pencils. Mr. Martin made a presentation of a summary of his report to ASTM D01.57 in January 2000.

The written report of the project, "The Identification of Organic Pigments in Colored Pencils," and the CDs accompanying it, are available from ASTM. Contact ASTM's D-1 Staff Manager, Tim Brooke, at The American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959; telephone (610) 832-9500: ask for ASTM Research Report Number D01-1116. Or, for further information, contact Mark Gottsegen, Chairman, ASTM D01.57, Department of Art, University of North Carolina at Greensboro, P.O. Box 26170, Greensboro, NC 27402-6170; telephone (336) 334-5571, fax (336) 674-7899, mdgottsegen@aol.com.