A frame that blocked the light
Garden of the Asylum
When the conservator removed the painting from the frame for research, she discovered different colours along the lower right edge. Where the frame protected the painting from light, the paint has a stronger purple colour.
Chemists analysed the paint and found the cause of the discolouration: a red lake pigment (brazilwood) that fades when exposed to light. Because of this fading, other parts of the painting now have different colours than Van Gogh originally intended.
Under the frame, along the bottom and sides (the image shows a detail of the lower right edge), the paint is a darker purple.
The purple layer at the top of this paint sample has faded to light blue as a result of exposure to light. Deeper in the paint sample, where the light could not reach, red lake pigments can still be found in the purple.
Cross-section of a paint sample from The garden of the asylum in Saint-Rémy
