The Pigment Analysis of 18th Century Pastel Paintings by Maurice-Quentin de La Tour (1704-1788) and Jean Valade (1710-1787)
Bibliographic record
Abstract
Pastel paintings are rarely studied unless they are unframed [1-3]. The conservation treatment of three French pastel portraits by Maurice-Quentin de La Tour (1704-1788) and Jean Valade (1710-1787) at the paper conservation studio of the National Museum of Sweden gave the opportunity to study the materials, with a particular focus on pigments, used by the artists in the 18th century. The artworks analysed consisted of a preparatory drawing and two finished pastels. The pastel pigments can also be found on the backboard of one pastel. The aim of the analysis was to learn about the materials used by two of the leading pastellists of the time and, in order to outline their colour palette, characterize the white filler and the pigments used as well as the binders.<br/>The combination of photographic analysis, including UV and infrared photographs, together with different spectroscopic techniques allowed to characterize part of the artists’ palettes, both pigment and possible binding medium, and to have information about the paper support. <br/>After a first non-invasive campaign by means of X-rays fluorescence spectroscopy (XRF), which allowed an overall elemental investigation of the different coloured areas, invasive analyses were conducted on a number of selected micro-samples through Fourier transformed infrared (FTIR) and Raman spectroscopy. 18th century pastels often consist of several layers of paper or parchment, canvas and a strainer or a backing board. As a result, the interpretation of the XRF data are often complicated requiring further specific analysis.<br/>The results obtained combining photographic techniques, elemental and molecular analyses are shown here and deeply discussed and compared with literary sources, such as the contemporary treatise on pastel painting by Paul Romain de Chaperon (1732-1793) published in 1788 [4].<br/>Acknowledgements <br/>This project was supported by the Wiros Fund, Sweden.<br/>References <br/>[1] Norville‐Day, H. et al., The conservator, 1993. 17(1): p. 46-55.<br/>[2] Townsend, J.H., The Paper Conservator, 1998. 22(1): p. 21-2.<br/>[3] Sauvage, L. and Gombaud, C., CATS Proceedings II, 2014: p. 31-45.<br/>[4] Chaperon, P.R., Traite de la peinture au pastel, 1788.<br/>
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".