Drying Oil and Natural Varnishes in Paintings: A Competition in the Metal Soap Formation

Metal soaps formation is a well-known issue in oil paintings. Along the lifetime of the painting, carboxylic acids coming from drying oil (free fatty acids, acids from hydrolysis of triglycerides and from oxidation processes) can react with cations of some pigments (in particular, smalt, lead white and zinc white) forming the related carboxylic salts. As observed by many authors, the formation of these carboxylates, with the tendency to migrate and to aggregate, not only modifies the behavior and the aspect of the paint film but also complicates the cleaning approach. In previous works we have demonstrated that a similar pigment reactivity is possible even in presence of natural resins (such as colophony, dammar, mastic, etc) historically used as final varnishes on paintings. In this case, in the reactions the terpenic acids, among the main components of the resins, are involved. In this work, the carboxylates formation kinetics has been studied starting from two representative acids (palmitic and abietic) of painting oils and natural varnishes. Successively, the reactivity of the palmitic acid with the potassium abietate and of the abietic acid with the potassium palmitate has been verified. This investigation aims at clarifying in which way terpenic acids can be involved in the metal soaps reactivity confirming that also surface varnishes may play a significant role in the carboxylates formation and reactivity. It is important to keep in mind that a finishing varnish can be removed and reapplied many times during the lifetime of a painting, thus renewing the provision of reactive terpenic acids at the interface of the painted layers.

Download Full-text

Formation of Metal Soaps In Oil Paintings Under Variable Environmental Conditions

10.21203/rs.3.rs-667290/v1 ◽

2021 ◽

Author(s):

M. Piovesan ◽

Marta Pérez-Estébanez ◽

M. San Andrés-Moya

Keyword(s):

Relative Humidity ◽

Environmental Conditions ◽

Metal Soap ◽

Oil Paintings ◽

Lead And Zinc ◽

Temperature Ageing ◽

Lead Zinc ◽

Metal Soaps ◽

Titanium White ◽

Cold Pressed

Abstract Formation of metal soaps in model paintings under cyclic temperature and relative humidity conditions has been studied by ATR-FTIR and compared with the standard controlled conditions generally maintained in many museums and storerooms. Three different white pigments (lead, zinc and titanium white) and two types of linseed oils (cold-pressed and alkali-refined) have been tested. The behaviour in short times (up to 6 weeks) depends on the pigment and environmental conditions. The relative humidity conditions have been shown to influence the metal soap formation in more degree than the temperature. Ageing under low cyclic relative humidity (30-50%) promotes metal soap formation in both lead and zinc white pigments, compared to high relative humidity (50-90%) conditions. Besides, the formation of zinc soaps continues for 6 weeks when low cyclic relative humidity is used, but it stops after 3 weeks under the other ageing conditions studied.

Download Full-text

Computational modelling of metal soap formation in historical oil paintings: the influence of fatty acid concentration and nucleus geometry on the induced chemo-mechanical damage

SN Applied Sciences ◽

10.1007/s42452-020-3038-z ◽

2020 ◽

Vol 2 (7) ◽

Author(s):

G. J. A. M. Eumelen ◽

E. Bosco ◽

A. S. J. Suiker ◽

J. J. Hermans ◽

A. van Loon ◽

...

Keyword(s):

Fatty Acid ◽

Acid Concentration ◽

Computational Modelling ◽

Mechanical Damage ◽

Fatty Acid Concentration ◽

Metal Soap ◽

Oil Paintings

Download Full-text

Chemical Composition of Natural Colophony from Pinus Brutia and Comparison with Synthetic Colophony

Natural Product Communications ◽

10.1177/1934578x1000501105 ◽

2010 ◽

Vol 5 (11) ◽

pp. 1934578X1000501 ◽

Cited By ~ 1

Author(s):

Ahmet C. Gören ◽

Gökhan Bilsel ◽

Alp Hakan Öztürk ◽

Gulaçtı Topçu

Keyword(s):

Chemical Composition ◽

Essential Oils ◽

Acid Content ◽

Resin Acids ◽

Capillary Gc ◽

Pinus Brutia ◽

Neoabietic Acid ◽

Natural Resins ◽

Main Components

The compositions of colophony resins obtained from Pinus brutia Ten trees by three different methods (acid paste, carved hole and scraping) from Ayvacık, Gökova and Kemalpaşa in Turkey were analyzed by capillary GC-MS. The main components were the monoterpenes α-pinene, β-pinene, and Δ3-carene, and the diterpenic resin acids palustric, abietic, kaur-9(11)-16-en-18-oic and neoabietic acid. The synthetic colophony resins exhibited similar contents to those of the natural resins obtained from the Gökova and Kemalpaşa regions of Turkey. However, colophony resins from Ayvacık exhibited only half the diterpenic acid content as those of the Gökova and Kemalpaşa resins. Out of the three techniques, the carved hole method caused rather different percentages in the constituents of the essential oils.

Download Full-text

Extraction of Material from Oil Paints by Solvents

MRS Proceedings ◽

10.1557/proc-712-ii1.7 ◽

2002 ◽

Vol 712 ◽

Cited By ~ 1

Author(s):

David Erhardt ◽

Roland H. Cunningham ◽

Sirpa Räsänen

Keyword(s):

Fatty Acids ◽

Saturated Fatty Acids ◽

Paint Film ◽

Short Chain Fatty Acids ◽

Solvent Exposure ◽

Crosslinking Process ◽

Oil Paints ◽

Paint Films ◽

Hydrolysis Of ◽

Soluble Material

ABSTRACTDrying oils used to formulate oil paints consist primarily of polyunsaturated triglycerides, along with smaller amounts of mono- and diglycerides, free fatty acids, and other compounds such as sterols. The drying of oils occurs through an oxidative crosslinking process that also produces smaller scission products such as short chain fatty acids and diacids. Compounds that are not attached to the crosslinked oil matrix include glycerin, the unreactive free saturated fatty acids and their glycerides, soaps of fatty acids produced by reaction with metal ions from the pigment, and scission products. As the oil ages, additional soluble material is produced by hydrolysis of glyceride esters. These relatively low molecular weight compounds can be extracted by exposure to solvents, as occurs during the cleaning of paintings. Excessive extraction of material canembrittle the paint film and affect the appearance of the paint. This paper examines the types and amounts of compounds extracted from oil paint films as a function of solvent, exposure time, pigment, and age of the paint. The results indicate that solvents vary more in the speed that they extract material than in their selectivity. The composition of the extracts is consistent with predictions based on the mechanisms of the drying and aging processes. These results confirm the importance of using the least polar solvent possible to clean paintings and to formulate varnishes.

Download Full-text

Study on the Characteristics of Materials and Manufacturing Techniques for the Mural Paintings in Daeunjeon at Ssanggyesa Temple, Jindo

Journal of Conservation Science ◽

10.12654/jcs.2021.37.6.09 ◽

2021 ◽

Vol 37 (6) ◽

pp. 701-711

Author(s):

Na Ra Lee ◽

Yeong Gyeong Yu ◽

Hwa Soo Lee

Keyword(s):

Paint Layer ◽

Particle Size Analysis ◽

Size Analysis ◽

Oil Painting ◽

Oil Paintings ◽

Drying Oil ◽

Painting Technique ◽

Mural Paintings ◽

Manufacturing Techniques ◽

Typical Soil

This study identifies the structure and material characteristics of the mural paintings in Daeungjeon at Ssanggyesa temple in Jindo by conducting scientific research and analysis including microscope examination, SEM-EDS, XRD, particle size analysis, and others. According to the analyses, the murals were considered to be of a typical soil mural style for Korean Buddhist murals, given that the walls were made of sand and soil and the murals had layers consisting of wall layers and a finishing layer. However, some finishing layer used calcite, while some ground layer used zinc white beneath the thick paint. In addition, there were similar features to those found on the surfaces of oil paintings such as cracks along with the paint layer, high gloss on surfaces, and thick brush strokes in many areas. It was found that the walls on which the murals were painted were made of soil but that the paint layer was created based on the oil painting technique using drying oil. It determined that the murals were painted in a unique painting style that is rarely found in other typical Buddhist murals in Korea.

Download Full-text

Photoluminescence Micro-imaging Sheds New Light on the Development of Metal Soaps in Oil Paintings

Metal Soaps in Art - Cultural Heritage Science ◽

10.1007/978-3-319-90617-1_12 ◽

2019 ◽

pp. 211-225

Author(s):

Mathieu Thoury ◽

Annelies Van Loon ◽

Katrien Keune ◽

Joen J. Hermans ◽

Matthieu Réfrégiers ◽

...

Keyword(s):

Oil Paintings ◽

Metal Soaps

Download Full-text

A Critical Review on the Analysis of Metal Soaps in Oil Paintings

ChemistryOpen ◽

10.1002/open.202100166 ◽

2021 ◽

Vol 10 (9) ◽

pp. 904-921 ◽

Cited By ~ 1

Author(s):

Francesca Caterina Izzo ◽

Matilde Kratter ◽

Austin Nevin ◽

Elisabetta Zendri

Keyword(s):

Critical Review ◽

Oil Paintings ◽

Metal Soaps

Download Full-text

Characterization of the oligopeptides of Parmigiano-Reggiano cheese soluble in 120 g trichloroacetic acid/1

Journal of Dairy Research ◽

10.1017/s0022029900030788 ◽

1994 ◽

Vol 61 (3) ◽

pp. 365-374 ◽

Cited By ~ 60

Author(s):

Francesco Addeo ◽

Lina Chianese ◽

Raffaele Sacchi ◽

Salvatore Spagna Musso ◽

Pasquale Ferranti ◽

...

Keyword(s):

Fast Atom Bombardment ◽

Potential Role ◽

Reversed Phase ◽

Exchange Chromatography ◽

Protein Nitrogen ◽

Main Components ◽

Hydrolysis Of ◽

Parmigiano Reggiano

SummaryThe non-protein nitrogen (NPN) of samples of Parmigiano-Reggiano cheese ripened for 6 and 15 months was fractionated by ion-exchange chromatography on a Cu2+-Chelex column to separate oligopeptides from free amino acids. Peptide components were isolated by reversed-phase HPLC and identified by fast atom bombardment–mass spectrometry (FAB–MS). Only the NPN fraction of 6 month old cheese samples contained enough peptides to be further characterized. On the basis of FAB–MS spectral results, 39 oligopeptides were identified, the main components being phosphopeptides. Two sets of both intact and partly dephosphorylated peptides, accounting for a total of 19 phosphopeptides, were formed by the hydrolysis of β–casein and belonged to regions 1–20 and 6–28 of β–casein. The formation and potential role of these peptides in cheese is discussed.

Download Full-text

Fatty Acids and Their Metal Salts: A Review of Their Infrared Spectra in Light of Their Presence in Cultural Heritage

Molecules ◽

10.3390/molecules26196005 ◽

2021 ◽

Vol 26 (19) ◽

pp. 6005

Author(s):

Anna Filopoulou ◽

Sophia Vlachou ◽

Stamatis C. Boyatzis

Keyword(s):

Fatty Acids ◽

Cultural Heritage ◽

Infrared Spectra ◽

Oil Paintings ◽

Sodium Calcium ◽

Zinc Salts ◽

Recorded Data ◽

Metal Soaps ◽

Archaeological Objects ◽

Organic Remains

In a cultural heritage context, fatty acids are usually found as breakdown products of lipid-containing organic remains in archaeological findings, binders in aged oil paintings, and additives in modern art-related materials. They may further interact with the ionic environment transforming into metal soaps, a process that has been recognized as a threat in aged paintings but has received less attention in archaeological objects. The investigation of the above related categories of materials with infrared spectroscopy can provide an overall picture of the organic components’ identity and demonstrate their condition and prehistory. The capability of investigating and distinguishing fatty acids and their metal soaps through their rich infrared features, such as the acidic carbonyl, the carboxylate shifts, the variable splits of alkyl chain stretching, bending, twisting, wagging, and rocking vibrations, as well as the hydroxyl peak envelopes and acid dimer bands, allows for their direct detailed characterization. This paper reviews the infrared spectra of selected saturated fatty monoacids and diacids, and their corresponding sodium, calcium, and zinc salts and, supported by newly recorded data, highlights the significance of their spectroscopic features.

Download Full-text