Synthetic Material Identification in Dorothy Liebes Textile Samples

Written by Kira Eng-Wilmot and Janet Lee

Fig. 1 Sample card, ca. 1967; Twill-woven wool, acrylic, nylon; Cooper Hewitt, Smithsonian Design Museum, Gift of the Estate of Dorothy Liebes Morin, 1972-75-111; Photo: Matt Flynn © Smithsonian Institution

This shocking pink-and-orange-striped fabric sample (Fig. 1) was designed by Dorothy Liebes presumably for Jasco Fabrics, but it also showcases the innovations of another client: DuPont. The fabric incorporates natural wool and synthetic acrylic and nylon fibers, but the casual observer might not be able to distinguish between them, and that is intentional. As a consultant to DuPont’s Textile Fibers Department, Liebes experimented with the department’s newly developed fibers and proposed changes to make the yarns more functional or interesting from the textile designer’s perspective. The manufacturers, in turn, manipulated the physical characteristics of the synthetic fibers to mimic the qualities of wool or other natural fibers. Only through magnification and analysis do the differences become clear.

Janet Lee, contract textile conservator, and Kira Eng-Wilmot, Cooper Hewitt’s textile conservator, analyzed and identified the fiber and plastic materials used in the Dorothy Liebes textiles in Cooper Hewitt’s collection. Polarized light microscopy techniques using an Olympus BX50 microscope and Fourier Transform Infra-red Attenuated Total Reflection (FTIR-ATR) spectroscopy with a Nicolet iS5 with OMNIC™ software were particularly useful in identifying the fibers found in this and other Liebes textile samples. As a consultant, Liebes had privileged access to novel fibers being invented by DuPont, so any less common synthetic fibers found in the group were prime candidates for in-depth research.

The weave alternates a fine orange warp with a bulkier bright-pink one. The orange warp is wool: under polarizing light microscopy, the tell-tale scale pattern and darker central core structure, known as a medulla, are visible (Fig. 2).

Fig. 2 Orange warp fibers seen under plane-polarized light with 20x magnification; Photo: Cooper Hewitt Textile Conservation

The pink warp and weft are acrylic, probably DuPont’s Orlon, the first mass-produced acrylic fiber. Both fibers have a distinct dog-bone shape under plane-polarized light microscopy (Fig. 3) and, under cross polars with the first order retardation 530 nanometer plate, demonstrate the distinct optical qualities of these birefringent fibers (Fig. 4). With fiber parallel to slow direction of first-order Red plate, the interference colors are yellow-orange; with fiber perpendicular to slow direction of first-order Red plate, interference colors are blue. Dark particles on the surface may indicate a delustrant, a substance used to dull the shine of a synthetic fiber. A comparison of period reference samples with FTIR analysis and written period descriptions shows a very strong correlation with Orlon acrylic (Fig. 5).

Fig. 3 Pink weft fiber cross section, embedded in cotton and nitrocellulose, seen under plane polarized light with 20x magnification; Fiber width of 72.5㎛; Photo: Cooper Hewitt Textile Conservation

Fig. 4 Pink weft fibers seen under crossed polars with first-order Red/530nm analyzer plate at 20x magnification; Photo: Cooper Hewitt Textile Conservation

Fig. 5 Pink weft fiber FTIR profile offset above the FTIR profile of a known Orlon sample, FTIR spectra analyzed with a Nicolet iS5-iD7 ATR with diamond crystal with 16 scans and OMNIC™ software; Photo: Cooper Hewitt Textile Conservation

The purple and orange wefts were identified as nylon, though they differ slightly. Under the bright field and cross section, the purple fiber has a trilobal shape, with one lobe distinctly darker than the others and a surface textured with parallel scribed lines (Figs. 6, 7). The orange weft is also a trilobal shape but is smaller, with a smooth surface and some pitting. After comparing these with period reference samples via FTIR analysis and written period descriptions, we believe these to be different versions of DuPont’s Antron, one of the company’s nylon 6,6 products (Fig. 8).

Fig. 6 Purple weft fibers seen under plane-polarized light with 20x magnification; Photo: Cooper Hewitt Textile Conservation

Fig. 7 Purple weft fiber cross section, embedded in cotton and nitrocellulose, seen under plane-polarized light with 20x magnification; Fiber width of 50㎛; Photo: Cooper Hewitt Textile Conservation

Fig. 8 Purple weft fiber FTIR profile offset above the FTIR profile of a known Anton sample, FTIR spectra captured and analyzed with a Nicolet iS5-iD7 ATR with diamond crystal with 16 scans and OMNIC™ software; Photo: Cooper Hewitt Textile Conservation

The analysis of this sample was part of a larger project undertaken to assess condition, perform materials analysis, and improve archival housing of the nearly 200 Dorothy Liebes textiles in Cooper Hewitt’s collection. Synthetics have been under-researched in the past, and Liebes’s role as a known materials innovator during a period that saw an explosion of new textile fibers, dyes, and finishes provided a unique opportunity to study synthetic and plastic materials used in weaving. This project received federal support from the Smithsonian Collections Care and Preservation Fund, administered by the National Collections Program and the Smithsonian Collections Advisory Committee.

A Dark, A Light, A Bright: The Designs of Dorothy Liebes is on view at Cooper Hewitt through February 4, 2024. Learn more about Dorothy Liebes and her work on the exhibition’s digital scholarship platform.

Kira Eng-Wilmot has been the Senior Textile Conservator since 2013. She holds an MA in fashion and textile studies: history, theory, and museum practice from the Fashion Institute of Technology and was previously a Samuel H. Kress Fellow at the Textile Conservation Laboratory at the Cathedral of St John the Divine and freelance conservator.

Janet Lee is a contract conservator specializing in the collection care of textiles, books, and paper.