Saponification in egg yolk-based tempera paintings with lead-tin yellow type I

Švarcová, Silvie; Kočí, Eva; Plocek, Jiří; Zhankina, Assel; Hradilová, J.; Bezdička, Petr

doi:https://dx.doi.org/10.1016/j.culher.2018.12.004

Number of the records: 1

Saponification in egg yolk-based tempera paintings with lead-tin yellow type I

1.

SYSNO ASEP	0500939
Document Type	J - Journal Article
R&D Document Type	Journal Article
Subsidiary J	Článek ve WOS
Title	Saponification in egg yolk-based tempera paintings with lead-tin yellow type I
Author(s)	Švarcová, Silvie (UACH-T)_{SAI, RID, ORCID} Kočí, Eva (UACH-T)_{SAI, RID} Plocek, Jiří (UACH-T)_{RID, ORCID, SAI} Zhankina, Assel (UACH-T)_SAI Hradilová, J. (CZ) Bezdička, Petr (UACH-T)_{SAI, RID, ORCID}
Source Title	Journal of Cultural Heritage. - : Elsevier - ISSN 1296-2074 Roč. 38, JUN (2019), s. 8-19
Number of pages	12 s.
Language	eng - English
Country	FR - France
Keywords	Saponification ; Lead-tin yellow ; Egg yolk ; Mixed lead carboxylates ; Pigment-binder interactions ; Gothic painting
Subject RIV	CA - Inorganic Chemistry
OECD category	Inorganic and nuclear chemistry
R&D Projects	GA17-15621S GA ČR - Czech Science Foundation (CSF)
Method of publishing	Open access with time embargo (01.07.2020)
Institutional support	UACH-T - RVO:61388980
UT WOS	000471746100002
EID SCOPUS	85060291182
DOI	10.1016/j.culher.2018.12.004
Annotation	Saponification occurring in paint layers of artworks represents a serious degradation process affecting the appearance and stability of paintings. Formation of metal soaps is mostly reported as a consequence of the interaction of lead white or zinc white with oil binder. We found the distinct symptoms of saponification in paint layers consisting of lead-tin yellow type I and egg yolk binder in a panel painting from the 15th century. This scarce finding induced the study of interactions between lead-tin yellow type I with three different binders: (i) egg yolk tempera, (ii) emulsion of egg yolk and oil, and (iii) oil. The interactions were studied in long-term model experiments using infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). Based on the results, a set of mixed lead carboxylates of the series Pb(C16)2-x(C18)x, where x = 0, 0.25, 0.5, 0,75, 1, 1.5 and 2, was synthesised as reference materials suitable as a basis for proper identification of neo-formed lead soaps by FTIR and XRD. The formation of lead soaps was detected already within 1 month of reaction in egg yolk containing binders, whereas no soap was formed during 6 months of the experiment in the oil mixture. The neo-formed soaps are various mixed lead carboxylates containing both palmitate (C16) and stearate (C18) in one crystal structure and the proportion of carboxylate anions is affected by the type of the binder. We found the C16:C18 ratio in mixed lead carboxylates is higher in egg yolk tempera samples in accordance with the more abundant palmitic acid in egg yolk fat. On the other hand, the lower C16:C18 ratio in emulsion binder correlates with increased content of stearic acid, suggesting contribution of both binders, i.e. egg yolk and oil, to the soap formation.
Workplace	Institute of Inorganic Chemistry
Contact	Jana Kroneislová, krone@iic.cas.cz, Tel.: 311 236 931
Year of Publishing	2020
Electronic address	http://hdl.handle.net/11104/0297117

Number of the records: 1