Varnish

The curing of drying oils at 60°C has been investigated by Fourier transform infrared spectroscopy and Fourier transform Raman analysis of linseed oil and poppyseed oil. In the first step, hydroperoxides are formed (broad vibration band centered around 3425 cm−1) with concomitant conjugation and cis-trans isomerization of the double bonds (disappearance of cis bands at 3011 and 716 cm−1, appearance of trans conjugated and trans nonconjugated bands at 987 and 970 cm−1). The subsequent decomposition of hydroperoxides in the presence of oxygen leads to the formation of alcohols (nitrite band at 779 cm−1 after nitrogen monoxide treatment), aldehydes (bands at 2810 and 2717 cm−1 in gas phase), ketones (saturated and unsaturated at 1720 and 1698 cm−1, respectively), carboxylic acids (saturated and unsaturated acid fluorides identified at 1843 and 1810 cm−1 after SF4 treatment), and peresters or γ-lactones (near 1770 cm−1). A rapid decrease in the double-bond concentration is recorded when curing continues, and the formation of epoxides, characterized by a vibration band at 885 cm−1, is observed. Thermolysis experiments have suggested the proposal of a reaction of addition of peroxyl radicals on the conjugated double bonds as a probable mechanism. This mechanism explains both the rapid disappearance of conjugated double bonds and the formation of epoxides as intermediate products observed in the initial step of curing.

In the present work, a study attempting to characterize the Manila elemi and Mexican copal resins from the Burseraceae family, which are used as components of varnishes and binding media of artworks, has been carried out. A new GC–MS method involving the use of methyl chloroformate as derivatisation reagent has been proposed. A second method which uses pyrolysis-GC–MS and hexamethyldisilazane

Infrared spectroscopy (FTIR) is a standard technique for the characterisation of organic materials in conservation science. This analytical technique is particularly interesting to analyse historical varnishes from cultural artefacts, as only minute samples are required. Some limitations apply, however, when analysing such chemically complex multi-component materials with interfering absorption bands. A previously introduced sample pre-treatment method using gaseous sulfur tetrafluoride SF4 has shown to widen the application fields of the IR-technique by improving its specificity. One of these new fields is its successful application to the characterisation of complex aged natural varnish and lacquer systems. The fluorination treatment leads to characteristic band shifts of four individual saturated and unsaturated acid groups attached at varying positions of the terpene backbone. This allows the separation of otherwise overlapping carbonyl bands of different ketones and ester groups. Based on this technique, inert and unique functional groups can be used as material specific markers to identify drying oil, shellac and different terpene resins in varnishes and lacquers. The proposed markers proved to be stable for several hundred years. These findings are particularly interesting, as it is now possible to trace such markers even in very old varnishes dating back to the 16th century – with a likewise simple technique.

Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the nineteenth century as a source of colorant to achieve lustrous golden glazes on tin- and silver-foiled objects and warm-toned finishes on musical instruments, such as violins. Aloe extracts contain characteristic anthraquinone and phenolic components which impart a distinctive orange tone and fluorescence to mixtures containing them. Because of the low concentration of colorant in the coatings and its probable degradation by high temperature during manufacture, the identification of aloe in heated oil–resin mixtures represents an analytical challenge. For this reason, the possible presence of aloe in glazes and coatings has been largely overlooked. This paper describes various analytical approaches to the identification of aloe in historic samples, from comparison with results obtained from reference standards and mock-up samples. Complementary analytical techniques including thermally assisted hydrolysis and methylation–gas chromatography–mass spectrometry, high-performance liquid chromatography, laser desorption–mass spectrometry, matrix-assisted laser desorption-ionization-mass spectrometry and surface-enhanced Raman scattering were used. Different chemical markers were identified by the individual methods and the advantages and limitations of each technique for the identification of aloe in oil–resin varnishes are discussed.

This study was performed to determine the impact of impregnation with boron compounds on the surface hardness of varnished wood materials. For this purpose, test specimens prepared from Oriental beech (Fagus orientalis Lipsky) and oak (Quercus petreae Lipsky), which met the requirements of ASTM D 358, were impregnated according to ASTM D 1413 with boric acid and borax by a vacuum technique. After impregnation, the surfaces were coated by cellulosic, synthetic, polyurethane, waterborne, acrylic, and acid hardening varnishes in accordance with ASTM D 3023. The surface hardness of the specimens after the varnishing process was determined in accordance with ASTM D 4366. According to the wood type, impregnation material, and varnish type, the surface hardness was highest for the oak impregnated with borax and acrylic varnish and lowest for the oak impregnated with borax and synthetic varnish. Therefore, impregnation with boron compounds showed an increasing impact on the surface hardness of the varnished wood. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The range of dermal exposure to non-volatile compounds during spray painting was studied in a semi-experimental study involving three enterprises and 12 painters. A fluorescent tracer was added to the paint and deposition of the tracer on clothing and uncovered parts of the skin was assessed using video imaging and processing techniques. A container (volume 36 m(3)) was sprayed with a colourless laquer (varnish) containing 66.7 mg/l fluorescent whitening agent. All painters sprayed the outside of the container. Nine painters repeated the painting a second time and five also sprayed the inside of the container. The painters wore white Tyvek coveralls, but no gloves. Duration of spraying the outside ranged from 4 to 21 min with a mean of 10 min and the amount of paint sprayed ranged from 3.0 to 12.8 l (mean 6.6 l). The mass of tracer deposited on the coverall ranged from 2.2 to 471 microg (90th percentile 256 microg), whereas, mass deposited on skin (i.e. the hands, wrists, and face) ...

This study determines the effects of the process of impregnation of boron compounds on the surface roughness of Oriental beech, Scotch pine, Oriental spruce, and Uludağ fir woods and varnished surfaces. For this purpose, samples are prepared according to ASTM D 358 and impregnated according to ASTM D 1413-99 with a 5.5% solution of boric acid (Ba), borax (Bx), and Ba with Bx (Ba + Bx) and varnished with synthetic varnish (Sv) and water-based varnish (Wb) in accordance with ASTM D 3023. The surface roughness is determined according to ISO 4287 and TS 930 standards. The results indicate that the surface roughness is the highest in Uludağ fir, Wb, and Bx and the lowest in Oriental spruce, Sv, and Ba + Bx. For the combination of wood, impregnation material, and varnish, the surface roughness is the highest in Oriental beech with Bx and Wb and the lowest in Scotch pine with Ba + Bx and Sv. The surface roughness is less in impregnated samples than unimpregnated samples and in impregnated and varnished samples than impregnated and unvarnished samples. According to these results, boron compounds decrease the surface roughness of varnishes and wood materials. Thus, impregnation of wood with boron compounds decreases the surface roughness. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4952–4957, 2006

This study has been performed for determining impacts of impregnation with Imersol-AQUA (I-AQUA) to yellow color tone of some softwoods and varnishes. For this purpose, samples of scotch pine (Pinus sylvestris L.), oriental spruce (Picea orientalis L.), and Uludağ fir (Abies bornmülleriana L.) wood, prepared according to the ASTM D 358 standards, are impregnated with I-AQUA by short-term (S), medium-term (M), and long-term (L) immersion techniques in accordance with ASTM D 1413 and producer's definition. After impregnation, surfaces have been coated by synthetic (Sv), acrylic (Ac), water-based varnishes (Wb) and polyurethane (Pu) varnishes in accordance with ASTM D 3023 standards. According to ASTM D 2244 standards, yellow color tone value of specimens after varnishing process was determined. As a result, based on the wood material, varnish type, and impregnation period, yellow color tone was the highest in pine, medium-term dipping, and synthetic varnish and the lowest in fir, long-term dipping, and water-borne varnish. Considering the interaction of wood type, period of impregnation and type of varnish, yellow color tone was the highest in fir + medium-term of dipping + synthetic varnish and the lowest in spruce + long-term of dipping + water-borne varnish. So, impregnation process, impregnation period, and varnishes applied during tests showed increasing impact for yellow color tone value of wood materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1048–1054, 2007

The reflectance factor of a diffuse plane background covered by a non-diffuse but partly absorbing layer is computed as a function of the incident and observer angles, and of the background reflectance factor. The particular case of back-scattering configuration is then studied. Numerical simulations are presented and discussed for a lambertian background and a transparent layer. Measurements with a gonio-spectrophotometer

Los electrodos rutilicos impermeabilizados se usan frecuentemente en la soldadura subacuatica por su buen comportamiento tecnologico. Una alternativa para mejorar su comportamiento seria incorporar compuestos quimicos a la capa de barniz. En el presente trabajo se presentan los resultados obtenidos con la adicion de una mezcla pirometalurgica exotermica en la primera capa de barniz de electrodos rutilicos del tipo 6013 y 7024. La mezcla pirometalurgica propuesta proporciona, por etapas, oxigeno al medio,segun la temperatura del revestimiento, alterando asi la presion parcial del hidrogeno del medio circundante. El elemento quimico portador de oxigeno en la mezcla pirometalurgia se reduce hasta su estado elemental, interactuandodespues con el bano de soldadura como desoxidante. Todo este proceso brinda un balance energetico favorable al proceso de soldadura. A 50 metros de profundidad se comparan el comportamiento tecnologico, la cantidad de poros en el metal de soldadura, la estruct...

In this study, the long-term (5-year) performances of 2 varnish systems, semitransparent alkyd-based brown stain (SABBS) and alkyd-based clear varnish (ABCV), were evaluated on preservative-treated Scots pine (Pinus sylvestris L.) sapwood. Prior to varnish application, specimens were impregnated with 2 different types of wood preservative. The experimental variables were varnish type, layer thickness, and wood preservative. ASTM D 1641 was followed for exposing wood specimens to outdoor conditions. The effects of long-term exposure on adhesion properties of applied varnish systems were tested according to ASTM D 4541. Long-term outdoor exposure resulted in 4.2% and 33.9% reductions in the adhesion properties of SABBS and ABCV varnish systems, respectively. The layer thickness and preservative type did not show any statistical reductions in adhesion properties.

Dammar, a natural triterpenoid resin, is widely used as a picture varnish in art technology. Several research workers have recently characterised its composition and oxidative degradation. Due to a lack of sensitivity, conventional thermal methods to characterise oxidation stability (like TGA and DSC) often require a high temperature regime. Chemiluminescence measurements turned out to be more sensitive (temperatures below 100 °C) and simultaneously allowed for better selectivity of the signal, which is directly coupled to the oxidation mechanism. The data collected here will enable an advanced kinetic modelling of Dammar degradation.

The extensive use of petroleum product has caused a number of environmental pollution. The printing industry is one of our nation’s largest producers of hazardous waste and volatile organic compound. One of the major alternatives is to use vegetable oil based products as biorenewable raw materials. Hence, the formulation of palm olein based varnish has been discussed in the present study. Palm olein from palm oil was prepared first, and their physical properties were determined. Varnishes were prepared with the palm olein and four different types of resin (F-2136, F-210, F-2110 and F-2118). Rheological properties, yield value, heptanes tolerance of the varnish were determined. From this study, it was found that palm olein with the F-210 resin is promising as the alternative varnish materials for the production of offset printing ink.

La réflexion sur le remplacement du traditionnel vernis à
la gomme-laque par une autre couche de finition a débuté en 2002
au C2RMF. Elle avait pour but de mettre en évidence les éventuelles
relations entre dégradation et composition du vernis, d’évaluer le
rôle de protection sur les bois de vernis de compositions différentes
et enfin d’étudier l’influence de la lumière sur l’évolution dans le
temps des bois ainsi vernis. L’expérimentation mise en oeuvre s’est
focalisée sur un vernis décrit dans L’Art du menuisier-ébéniste
publié par André-Jacob Roubo en 1774. Plusieurs tests de mesure
d’épaisseur, d’apparence et de propriété mécanique ont été réalisés
sur des éprouvettes de bois de placage recouverts du vernis
sélectionné. Les résultats encourageants de son effet protecteur à la
photo-oxydation et à l’oxygène de l’air ont permis de mettre en place
un protocole en vue de son application comme protection de surface
pour le mobilier en marqueterie de métal du musée du Louvre.
Reflection on replacing traditional shellac varnishes
with another finish began in 2002 at the C2RMF. The aim was to
highlight the possible relationship between deterioration and the
composition of the varnish, to assess the role played by protective
coatings made of different ingredients on wood and, lastly, to study
the long-term effects of light on woods thus varnished. The
experiments conducted focused on a varnish described in L’Art du
menuisier-ébéniste, published by André-Jacob Roubo in 1774.
Several tests to measure thickness, appearance and mechanical
properties were carried out on samples of veneer coated in the
selected varnish. The encouraging results of its resistance to photooxidation
and the oxygen in the air enabled us to establish a
protocol for applying it to protect the surface of the metal marquetry
furniture now in the Louvre.

El estudio muestra en qué grado dos técnicas pictóricas, acuarela y pigmentos aglutinados al barniz (Gamblin), utilizadas en la reintegración cromática de obras arte, experimentan un cambio de color tras ser barnizadas. El método de trabajo ha consistido en aplicar dos tipos de barniz, mate y brillante, sobre diferentes muestras de color de cada una de las dos técnicas pictóricas analizadas. El análisis colorimétrico realizado sobre las muestras barnizadas y el estudio comparativo de los resultados obtenidos permiten conocer hasta qué punto se produce un cambio de color sobre cada una de ellas y qué parámetro claridad, croma o tono es el que tiene mayor influencia en el cambio.

The purpose of this 1994 workshop was to introduce participants to traditional and modern varnishes and to compare their characteristics and handling properties. Twelve test panels from the workshop were brought to the Centre de conservation du Québec (CCQ) in Quebec City and mounted on a wall in the paintings lab, where they were left to age for fifteen years. Visual comparisons were made to evaluate differences in colour change and gloss. It was concluded that adding Tinuvin 292 to mastic and dammar varnishes to inhibit premature yellowing (in the absence of UV light) is very important since all unstabilized varnishes made with these resins discoloured to some degree. Most proprietary varnishes showed no discoloration. However, those based on ketone resins gave less consistent results. It was particularly encouraging to see how well the Regalrez 1094 samples have aged. Their superior performance with regard to yellowing (with or without the addition of Tinuvin 292) and their rapid solubility in isooctane after 15 years of natural ageing may make Regalrez a suitable varnish for acrylic paintings. Surprisingly, four different unstabilized varnishes based on copal-oil formulations show only a trace of discoloration. It remains to be determined how these varnishes would age in environments where UV light is not filtered. Cet article fait un constat sur le vieillissement naturel d'échantillons de vernis appliqués sur des panneaux peints, créés lors de l'atelier de l'ICC en 1994. Le but de l'atelier était de faire connaître aux participants des vernis traditionnels et modernes et de les comparer. Un jeu de douze panneaux a été exposé pendant quinze ans sous les conditions ambiantes de l'atelier des peintures au Centre de conservation du Québec. Les observations présentées sont des évaluations comparatives faites par des restaurateurs. En conclusion, lors de l'emploi du mastic ou du dammar, il est essentiel d'ajouter un stabilisant, comme le Tinuvin 292, afin d'empêcher le jaunissement prématuré de ces vernis (en l'absence de rayons ultraviolets). Ces mêmes résines non stabilisées ont toutes jauni. Il est rassurant de constater que la plupart des vernis synthétiques testés n'ont pas jauni. En contrepartie, la qualité du vieillissement de vernis à base de résine cétone demeure incertaine. Le Regalrez 1094 a donné un très bon rendement, sans ou avec l'ajout de Tinuvin 292. Sa solubilité rapide dans des hydrocarbures, tels que l'isooctane, faciliterait son application ainsi que son retrait éventuel des peintures acryliques. Quatre vernis différents à base d'huile-copal (non stabilisés) ne démontrent qu'un soupçon de jaunissement. Il reste à savoir quel type de vieillissement auraient présenté tous ces vernis sous une quantité appréciable de lumière ultraviolette.