This multidisciplinary project examined the composition, materials, and historical context in which Irises was painted to gain a deeper understanding of Van Gogh’s process and how the painting has changed over time.

• An understanding of what pigments Van Gogh used in Irises, how he applied them, and how they may have changed over time.
• Evidence that color changed in some pigments in Irises, particularly resulting in the irises appearing blue to viewers today rather than violet, as Van Gogh originally painted them.
• A results-informed 3D-printed color-adjusted reconstruction to unveil how Irises may have originally appeared.
• Presentation of technical analysis for all audiences via the exhibition Ultra-Violet: New Light on Van Gogh’s Irises, on view October 1, 2024–January 19, 2025. The exhibition was part of Getty’s collaborative project PST ART: Art & Science Collide.

About Irises
Vincent Van Gogh painted Irises in May 1889, the day after he entered Saint-Paul de Mausole psychiatric hospital just outside of Saint-Rémy-de-Provence, France. He had been suffering from failing mental health and entered the asylum willingly. The head doctor at the time, Dr. Théophile Peyron, allowed Van Gogh to work from nature in the asylum’s garden to aid in his recovery.

Van Gogh and Color Theory
Van Gogh’s ideas about color theory played a crucial role in his art. Central to his understanding was the work of French chemist Michel-Eugène Chevreul, whose law of simultaneous color contrast describes how our perception of a particular color is affected by other colors nearby. Chevreul posited that each color has a specific complementary color. For example, red, yellow, and blue are complemented by green, violet, and orange, respectively. According to Chevreul, the juxtaposition of a primary color with its complementary secondary color—yellow next to violet, for instance—intensifies both.

Scientists utilized both invasive and non-invasive techniques to identify which pigments Van Gogh used. Getty staff also traveled to Saint-Paul de Mausole and were able to see the garden where Van Gogh painted – which has changed very little in the last 150 years – confirming that the irises were in fact a deep violet color rather than blue, as they appear today.

Technical Imaging
Several technical imaging processes were used to study Irises including:

• Visual examination (with magnification) to examine the surface of the painting
• X-Radiography to visualize the canvas weave and reveal changes made during painting
• 3D imaging using photogrammetric process to capture color and texture
• X-ray fluorescence scanning to map the distribution of chemical elements present in the paints, helping us to infer which pigments were used
• Fiber optics reflectance spectroscopy, gas chromatography mass spectrometry, and Raman spectroscopy to provide molecularly specific material identification
• Microfade testing to determine whether specific colors in the painting were vulnerable to light

3D Printed Color Reconstruction
Knowing which pigments Van Gogh used, and how they changed over time, allowed us to approximate the original colors of Irises. Categorizing similar sections of pigment color, followed by subdivision by level of color change, isolated fine areas for color adjustments. High-resolution images enabled intricate color adjustments that were responsive to individual brush strokes and paint color mixing, resulting in realistic color gradations that were applied to a 3D model which was subsequently printed.

Vincent Beltran, Scientist, Getty Conservation Institute
Johana Herrera, Lead Imaging Technician, Center Imaging Studio
Kayla Kee, Senior Digital Imaging Specialist, Center Imaging Studio
Olivia Kuzio, Assistant Scientist, Getty Conservation Institute
Joy Mazurek, Associate Scientist, Getty Conservation Institute
Devi Ormond, Associate Conservator of Paintings, Getty Museum
Catherine Patterson, Scientist, Getty Conservation Institute
Todd Swanson, Assistant Director, Digital Imaging
Michelle Tenggara, Graduate Intern of Paintings Conservation, Getty Museum
Karen Trentelman, Senior Scientist, Getty Conservation Institute

Acknowledgments
Factum Foundation
National Gallery of Art
Van Gogh Museum
Thread Count Automation Project