by Ioana Maria Cortea — Last updated on October 22, 2025 — Reading time: 10 min
The INFRA-ART Spectral Data Collections is a blog article series that highlights key groups of art-related materials represented in the INFRA-ART Spectral Library. Each article focuses on a specific material category—examining its composition, technical details, and history of use—while also showcasing the spectral data collections available within the INFRA-ART database. By connecting material knowledge with accessible spectral reference data, the series aims to support research, education, and interdisciplinary engagement across the cultural heritage field.
Watercolor is among the most familiar and widely practiced painting media, yet its material behavior is uniquely complex — highly responsive to light, moisture, paper chemistry, and pigment composition. Unlike opaque paint films, watercolor layers remain transparent and comparatively fragile, relying on the reflectance of the underlying support rather than the opacity of a binder. In technical terms, watercolor is a stain diffused into the upper fibers of paper more than a continuous film built on its surface. This makes the medium particularly suitable for spectral study: its optical response is influenced not only by the intrinsic optical properties of the pigments but also by the microstructural features of the underlying support.
Previous posts in this watercolor series examined the historical development of watercolors, from early aqueous media to the sophisticated palettes and papers of the 18th and 19th centuries. Drawing on this background, the present article introduces the watercolor collection available in the INFRA-ART Spectral Library, developed to support technical art history, conservation research, and machine-learning–based material identification.
WATERCOLORS in the INFRA-ART Database
The INFRA-ART watercolor dataset compiles multi-analytical spectra from a wide range of historically and artistically significant pigments prepared following traditional watercolor practice. The current collection includes over 70 samples sourced from Winsor & Newton Professional Watercolour, the Cotman Watercolour series, and selected colors from Winsor & Newton Designers Gouache. Representing one of the most widely used commercial systems in contemporary artistic practice, these materials encompass a broad spectrum of pigment types—traditional earths, mineral-based blues and greens, historical and modern organics, synthetic azo and quinacridone pigments, phthalocyanines, cadmiums, cobalt colors, and mixed formulations characteristic of commercial watercolor production.
Prepared according to standardized watercolor procedures, these samples capture the full diversity of watercolor optical behavior, including highly transparent washes, semi-opaque formulations, and fully opaque gouache paints. Because each formulation reflects not only pigment identity but also manufacturing variables—such as pigment particle size distribution, proprietary binder proportions, and additives influencing flow or opacity—the collection provides insight into the material complexity of contemporary watercolor systems.
At present, the database includes ATR-FTIR and XRF datasets for all samples, enabling correlation between molecular/binder signatures (via ATR-FTIR) and elemental pigment composition (via XRF). These datasets offer reliable foundations for pigment identification, mixture analysis, and comparative studies across professional and student-grade formulations. Additional Raman spectroscopy and SWIR reflectance data are planned for future expansion, with ongoing updates to broaden both chromatic coverage and analytical completeness.
Watercolor samples and available spectral data in the INFRA-ART Spectral Library
Professional Watercolor
| Sample name | Color Index | Sample ID | Supplier | Spectral data |
| Alizarin Crimson | PR 83 | WN0101004 | Winsor & Newton | FTIR, XRF |
| Aureolin | PY 40 | WN0101016 | Winsor & Newton | FTIR, XRF |
| Burnt Sienna | PR 101 | WN0101074 | Winsor & Newton | FTIR, XRF |
| Cerulean Blue | PB 35 | WN0101137 | Winsor & Newton | FTIR, XRF |
| Chinese White | PW 4 | WN0102150 | Winsor & Newton | FTIR, XRF |
| French Ultramarine | PB 29 | WN0101263 | Winsor & Newton | FTIR, XRF |
| Ivory Black | PBk 9 | WN0101331 | Winsor & Newton | FTIR, XRF |
| Lemon Yellow | PY 53 | WN0101347 | Winsor & Newton | FTIR, XRF |
| Olive Green | PY 65 + PB 15:6 + PR 101 | WN0101447 | Winsor & Newton | FTIR, XRF |
| Payne’s Gray | PB 15 + PBk 6 + PV 19 | WN0101465 | Winsor & Newton | FTIR, XRF |
| Permanent Rose | PV 19 | WN0101502 | Winsor & Newton | FTIR, XRF |
| Permanent Sap Green | PG 36 + PY 110 | WN0101503 | Winsor & Newton | FTIR, XRF |
| Raw Sienna | PY 42 + PR 101 | WN0101552 | Winsor & Newton | FTIR, XRF |
| Viridian | PG 18 | WN0101692 | Winsor & Newton | FTIR, XRF |
| Winsor Blue | PB 15 | WN0101707 | Winsor & Newton | FTIR, XRF |
| Winsor Red | PR 254 | WN0101726 | Winsor & Newton | FTIR, XRF |
| Winsor Violet | PV 23 | WN0101733 | Winsor & Newton | FTIR, XRF |
| Winsor Yellow | PY 154 | WN0101730 | Winsor & Newton | FTIR, XRF |
| Yellow Ochre | PY 43 | WN0101744 | Winsor & Newton | FTIR, XRF |
Cotman Watercolor
| Sample name | Color Index | Sample ID | Supplier | Spectral data |
| Alizarin Crimson Hue | PR 206 | WN0301003 | Winsor & Newton | FTIR, XRF |
| Burnt Sienna | PR 101 | WN0301074 | Winsor & Newton | FTIR, XRF |
| Burnt Umber | PBr 7 + PY 42 | WN0301076 | Winsor & Newton | FTIR, XRF |
| Cadmium Orange Hue | PO 43 + PY 83 | WN0301090 | Winsor & Newton | FTIR, XRF |
| Cadmium Red Deep Hue | PR 188 + PR 254 | WN0301098 | Winsor & Newton | FTIR, XRF |
| Cadmium Red Hue | PR 149 + PR 255 | WN0301095 | Winsor & Newton | FTIR, XRF |
| Cadmium Red Pale Hue | PR 255 + PY 65 | WN0301103 | Winsor & Newton | FTIR, XRF |
| Cadmium Yellow Hue | PY 65 + PY 97 | WN0301109 | Winsor & Newton | FTIR, XRF |
| Cadmium Yellow Pale Hue | PY 175 + PY 65 | WN0301119 | Winsor & Newton | FTIR, XRF |
| Cerulean Blue Hue | PB 15 | WN0301139 | Winsor & Newton | FTIR, XRF |
| Chinese White | PW 5 | WN0301150 | Winsor & Newton | FTIR, XRF |
| Cobalt Blue Hue | PB 29 + PW 5 | WN0301179 | Winsor & Newton | FTIR, XRF |
| Dioxazine Purple | PV 23 | WN0301231 | Winsor & Newton | FTIR, XRF |
| Emerald | PG 7 + PY 175 | WN0301235 | Winsor & Newton | FTIR, XRF |
| Gamboge Hue | PR 209 + PY 150 | WN0301266 | Winsor & Newton | FTIR, XRF |
| Hooker’s Green Dark | PB 15 + PG 7 + PY 139 | WN0301312 | Winsor & Newton | FTIR, XRF |
| Hooker’s Green Light | PB 15 + PG 7 + PY 139 | WN0301314 | Winsor & Newton | FTIR, XRF |
| Indian Red | PR 101 | WN0301317 | Winsor & Newton | FTIR, XRF |
| Indigo | PB 15 + PB 29 + PBk 7 | WN0301322 | Winsor & Newton | FTIR, XRF |
| Intense Phthalo Blue | PB 15 | WN0301327 | Winsor & Newton | FTIR, XRF |
| Intense Phthalo Green | PG 36 | WN0301329 | Winsor & Newton | FTIR, XRF |
| Ivory Black | PBk 9 | WN0301331 | Winsor & Newton | FTIR, XRF |
| Lamp Black | PBk 6 | WN0301337 | Winsor & Newton | FTIR, XRF |
| Lemon Yellow Hue | PY 175 | WN0301346 | Winsor & Newton | FTIR, XRF |
| Light Red | PR 101 | WN0301362 | Winsor & Newton | FTIR, XRF |
| Mauve | PR 122 + PV 23 | WN0301398 | Winsor & Newton | FTIR, XRF |
| Payne’s Gray | PB 15 + PB 29 + PBk 7 | WN0301465 | Winsor & Newton | FTIR, XRF |
| Permanent Rose | PV 19 | WN0301502 | Winsor & Newton | FTIR, XRF |
| Prussian Blue | PB 27 | WN0301538 | Winsor & Newton | FTIR, XRF |
| Purple Lake | PV 19 | WN0301544 | Winsor & Newton | FTIR, XRF |
| Raw Sienna | PR 101 + PY 42 | WN0301552 | Winsor & Newton | FTIR, XRF |
| Raw Umber | PBr 7 + PY 42 | WN0301554 | Winsor & Newton | FTIR, XRF |
| Rose Madder Hue | PR 206 | WN0301580 | Winsor & Newton | FTIR, XRF |
| Sap Green | PG 36 + PR 101 + PY 139 | WN0301599 | Winsor & Newton | FTIR, XRF |
| Sepia | PBk 7 + PBr 7 | WN0301609 | Winsor & Newton | FTIR, XRF |
| Turquoise | PB 15:3 + PG 7 | WN0301654 | Winsor & Newton | FTIR, XRF |
| Ultramarine | PB 29 | WN0301660 | Winsor & Newton | FTIR, XRF |
| Vandyke Brown | PBr 7 + PR 101 | WN0301676 | Winsor & Newton | FTIR, XRF |
| Viridian Hue | PG 7 | WN0301696 | Winsor & Newton | FTIR, XRF |
| Yellow Ochre | PY 42 | WN0301744 | Winsor & Newton | FTIR, XRF |
Designers Gouache
| Sample name | Color Index | Sample ID | Supplier | Spectral data |
| Alizarin Crimson | PR 83 | WN0605004 | Winsor & Newton | FTIR, XRF |
| Bengal Rose | PR 169 | WN0605028 | Winsor & Newton | FTIR, XRF |
| Brilliant Red Violet | PV 1 | WN0605050 | Winsor & Newton | FTIR, XRF |
| Cadmium Lemon | PY 35 | WN0605086 | Winsor & Newton | FTIR, XRF |
| Cerulean Blue | PB 35 | WN0605137 | Winsor & Newton | FTIR, XRF |
| Cobalt Blue | Pb 28 | WN0605178 | Winsor & Newton | FTIR, XRF |
| Cobalt Turquoise Light | PG 50 | WN0605191 | Winsor & Newton | FTIR, XRF |
| Perylene Black | PBk 31 | WN0605505 | Winsor & Newton | FTIR, XRF |
| Prussian Blue | PB 27 | WN0605538 | Winsor & Newton | FTIR, XRF |
| Rose Tyrien | PR 173 | WN0605593 | Winsor & Newton | FTIR, XRF |
| Ultramarine | PB 29 | WN0605660 | Winsor & Newton | FTIR, XRF |
| Zinc White | PW 5 | WN0605748 | Winsor & Newton | FTIR, XRF |
How to cite this resource
Cortea, I.M. (2025, Oct 22). INFRA-ART spectral data collections: watercolors. INFRA-ART Blog.
