1. Analysis of ancient materials and their degradation – Lecture 7 MSE-482 Prof. Dr. Claire Gervais

2. Case-study: hidden portrait revealed by X- ray fluorescence techniques

3. MSE-482 – L7 Slide 3 Why / what / where / how? WHY? – Access to hidden painting give information about making of artworks by Van Gogh and its conceptual changes (former period revealed) – Specific to Van Gogh, allows comparison with preparatory drawings and abundant literary record

4. MSE-482 – L7 Slide 4 Why / what / where / how? WHAT? – Van Gogh would often paint new composition on top of existing work. – Head appearing behind “Patch of Grass” (~ 1886-1887, Paris period) – Old painting / layer of lead white / New painting – Identify pigments and their distribution within the head to reconstruct its image

5. MSE-482 – L7 Slide 5 Why / what / where / how? WHERE? – Below new painting and lead white layer : need to analyze in depth – Painting of 30 x 40cm with head in square 17.5x17.5cm2 : need large field of view – Micro-samples extracted for pigment characterization (ca 0.7mm): need high S/N ratio and spatial resolution Use of complementary imaging and spectroscopy techniques

6. MSE-482 – L7 Slide 6 Exercise: Find out the techniques and their modalities used to analyze the composition of the hidden painting in Van Gogh For each technique: 1.Schematic drawing of the experimental setup 2. Why: reason to chose this technique 3. How: reason to chose this setup

7. MSE-482 – L7 Slide 7 Step 1: XRF imaging of the head

8. MSE-482 – L7 Slide 8 Color partial reconstruction of the head