A multi-analytical study of lead white darkening in master drawings at the National Gallery of Denmark
Notice bibliographique
Résumé
Old master drawings are precious artworks that are treasured for their aesthetic value and historical significance. They often feature white highlights, which are typically created using lead white, one of the most used historical white pigments. However, many of these highlights have discoloured over time, becoming dark brown or black due to unclear degradation processes. This phenomenon not only misrepresents the original artworks, but also detracts from their beauty, diminishes their longevity and threatens their suitability for public display. To ensure their preservation, it is essential to determine why some lead white highlights in these artworks retain their light tones while others are prone to darkening. The LeadMad project coordinated by the National Gallery of Denmark aims at advancing preventive conservation of old master drawings by identifying the relationships between the composition, provenance, and production methods of lead white pigments as well as the environmental factors that contribute to their discoloration on drawings, lithographs and early photographs. To gain a deeper understanding of the problem and develop possible solutions, selected samples and objects were examined using a variety of analytical techniques such as X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRPD), Raman spectroscopy, and isotope geochemical investigations. These methods allowed us to inspect the darkening of lead white at an elemental, molecular, and micro-structural level. XRF analyses confirmed the presence of lead as the main element in the majority of the highlights, while XRPD measurements identified both cerussite and hydrocerussite in the white highlights. Moreover, galena, a black crystalline compound, and anglesite were associated with the darkened highlights. Raman spectroscopy assisted in the identification of white and dark compounds, while isotope analyses identified three main groups of raw materials. Through these measurements, the lead white pigments were classified according to their physicochemical properties in relation to the raw materials used, the fillers and binders added, and the geographical/temporal origin. Additionally, monitoring of storage conditions, which play a crucial role in the darkening process, identified relative humidity and concentrations of airborne pollutants as key factors. The research conducted thus far has provided a deeper understanding of the degradation process of lead white pigments and has helped formulate hypotheses for upcoming experiments that will aid in advancing preventive conservation efforts for these precious artworks. These findings will be of great value to museums, conservators, and other stakeholders in the field of art conservation.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,003 | 0,002 |
| Études des sciences et des technologies | 0,002 | 0,001 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».