Navigation – Plan du site
Dossier

Testing on mock-ups and on paintings of innovative polymeric gels for surface cleaning

Giulia Rollo

Résumés

Les recherches pour mon diplôme en Conservation et Restauration ont porté sur un nouveau type  de gels polymériques hydro-organiques pour le nettoyage des surfaces. La caractéristique principale de ces systèmes est leur haute élasticité, qui permet de les ôter des surfaces où ils sont appliqués par un mécanisme de peeling ou épluchage. L’évaluation de ces nouveaux outils a été faite à travers plusieurs tests, sur des maquettes et des cas réels. Les résultats positifs ont démontré que ils pourraient  représenter, dans le futur, une alternative valable aux systèmes de nettoyage traditionels.

Haut de page

Texte intégral

The major part of this Master thesis was made possible by the contribution ofthe Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI, Firenze, Italy) inproviding the gel formulations employed. In particular the author expresses her gratitude to Professor Luigi Dei, Dr. Emiliano Carretti and Dr. Irene Natali, all from University of Firenze, for the continuous and valuable support during all the work.

The author is also thankful to Dr. Tommaso Poli for the scientific analysis, to directors and staff of Restoration, Scientific and Diagnostic laboratories of the Centro Conservazione e Restauro (CCR) “La Venaria Reale” and Dr. Michela Palazzo of the Scuola di Alta Formazione of the CCR for their cooperation and assistance.

Thanks are due to the Soprintendenza per i Beni Storici, Artistici ed Etnoantropologici del Piemonte, and in particular to Dr. Edith Gabrielli, Dr. Clelia Arnaldi and Dr. Mario Epifani, who allowed the realization of the tests on the artworks.

Introduction

1Gels for cleaning purposes have been largely used in the last three decades. Formulations based on poly(acrylic acid) (PAA) are probably the most employed on painted surfaces, together with gels containing cellulose ethers (KHANDEKAR 2000). For these systems, and in particular for Solvent gels, the residue question represents the main problem (STULIKet al. 2004). In fact, the treatment with these materials requires the use of a liquid solvent and a fairly strong mechanical action to minimize the residues left onto the painted surfaces. In the last years the interest for the so-called “rigid gels”-aqueous systems formed from biopolymers- increased also for the cleaning of polychrome artworks (CAMPANIet al. 2007). Compared to traditional poultices, these highly viscous formulations are able to release liquids (water solutions) on the surfaces very gradually. Furthermore, analytical studies detected only trace amounts of residual components from these gels on treated areas. Even if the literature relating with these systems and their employ is growing, they are not yet commonly used for this kind of surfaces. One reason is the problem concerning the inclusion of organic solvents into their polymeric networks, as these liquids actually remain the most used cleaning agents for the removal of many materials from the surface of artworks.

  • 1  In this work, with the definition of “gel” we refer to the high viscosity polymeric solutions/disp (...)

2A new category of hydro-organo gels characterized by a solid-like appearance has been invented at the Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), research unit of the Chemistry Department, University of Firenze. During the last five years, these innovative cleaning tools for artworks have been tuned with the aim of minimizing the effects of cleaning on the painted surfaces (CARRETTIet. al. 2009, CARRETTIet. al. 2010)1.

3The gels of interest are formed by a polymeric network of poly(vinyl alcohol-co-vinyl acetate) copolymers with different hydrolysis degree cross-linked by a salt, borax, in which water/organic solvent mixtures are dispersed. Those systems have peculiar characteristics, such as high viscous behaviour and strong elasticity that are particularly interesting. The first one affects the controlled release of cleaning agents throughout the pictorial layers. Both characteristics allow to peel the cleaning tool off from a surface after their application in a single step.

Fig. 1 Removal of hydrogels by peeling them off of a glass surface by means of a spatula

Fig. 1 Removal of hydrogels by peeling them off of a glass surface by means of a spatula

On the left a PVA-borax gel. On the right: a PAA gel.

Credits: Carretti et al., 2009.

4The so-called “peel-off ability” allows to minimize the mechanical action on the surface and cleaning occurs without leaving any detectable polymer or borax-derived residue (as confirmed by specific analysis on treated surfaces).

5The most recent formulations employ a random copolymer containing ca. 20% of vinyl acetate and ca. 80% of vinyl alcohol groups (80PVA: poly(vinyl alcohol), 80% OH). Small amounts of this polymer (3-4 wt%), of borax (< 1 wt %) and concentrations for up to 50% of solvents miscible in water and commonly used in conservation practice - such as alcohols and ketones- produce gels quite stiff which can be evenly spreaded on surfaces, being as well transparent and colourless (NATALIet al. 2011).

6My research has focused on testing 80PVA/borax gels for removing superficial coatings of different natural varnishes from mock-ups. Gels containing four different solvents - isopropanol, ethanol, acetone and metiletilketone- at different weight % contents and characterized by various 80PVA/borax weight ratios -in order to compare formulations with different rigidities- have been used. These same gels have been also tested on artworks, on an oil-on-wood painting (dating from the XVI century) and an oil-on-canvas painting (dating from the XVIII century), both characterized by layers of yellowed and deteriorate varnishes. The aim of the work was to evaluate the potential of these systems for the cleaning practice in relationship to the conservation problems. For that reason, macroscopic behaviours - like the performance in cleaning action, the application/removal from the surfaces, the potential to be manipulated- of several gels have been studied.

7This paper reports on the application of gels on mock-ups coated with mastic varnish, and gives a brief description of the test performed on the paintings.

Materials and methods

Preparation of gels

8All the gels have been prepared for the work by the researchers of the Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), according to the procedure described in the literature (NATALIet al. 2011).

9Before use, all gels have been submitted to a validation protocol through chemical and physical measurements, in order to verify their characteristics, according to literature recommendations (NATALIet al. 2011). In particular, rheological and liquid release measurements have been performed, in order to control in advance the proper functioning of the systems in terms of the peelability and cleaning action.

Preparation and characteristics of the mock-ups

10Ten mock-ups measuring 5 cm x 2.5 cm x 1 cm have been prepared using a substrate covered by a thin layer of mastic varnish.

  • 2  Balsite® CTS technical data sheet.

11The substrates have been realized with a mixture of an epoxy resin, Balsite® (CTS, Milano), and titanium white (pigment in powder, Zecchi, Firenze). Balsite® has been prepared according to the procedure described in literature2 and after titanium white has been added to the still fresh resin (20 wt %). A small amount of ethanol (denaturated with 1% cycloexane, Sigma-Aldrich) was added in the phase of the processing in order to make more fluid the mixture. The material has been poured into silicone molds, where it started to solidify. Drying of the substrates occurred in normal environmental conditions (at 20°C and 55 % R.H.) for 24 hours and in a drying oven with forced air (at 60°C) for the next 48 hours.

  • 3 Tests with free solvents, colorimetry and gravimetry measuremens.
  • 4 Preparation and drying according to the procedure described in literature,Balsite® CTS technical da (...)

12Balsite® is commonly used in conservation of wood and it has been chosen in this context for some of her peculiar characteristics. Several tests3 conducted on a sample of dry material4 demonstrated that the final product is strongly resistant to the action of a wide variety of organic solvents, it is stable to light, oxygen and thermo-igrometrical fluctuations, and it dryes quickly. Furthermore, pigments in powder can be easely incorporated to the resin during its preparation process and the samples of dryed material are characterized by fairly homogeneous surfaces.

13Titanium white in the mixture gives the substrates a white colour (the resin is itself light-coloured) and prevents the phenomena of fluorescence characteristic of the Balsite®.

Fig. 2 Surface of a substrate realized with the mixture of Balsite® and titanium white

Fig. 2 Surface of a substrate realized with the mixture of Balsite® and titanium white

Photographs under visible light (left) and UV light (right).

Credits: ©Rollo 2012.

14The inhibition of the fluorescence of the substrates was necessary for the analysis under UV light of the cleaning performed by the gels (only the fluorescence of the overlying varnish layer should be detectable).

15The mastic varnish has been prepared using Chios mastic pearls (Zecchi, Firenze) and Turpentin spirit (Zecchi, Firenze), at the weight ratio 1/4. When the the resin was completely dissolved (after one month of storage in a dark room) the varnish has been applied on the ten substrates with a soft brush in order to form an homogeneous and thin layer.

16Drying of the mock-ups took place in normal environmental conditions (at 20°C and 55 % R.H.). Accelerated ageing has been performed in solar box (λ > 295 nm) for 500 hours.

17After the treatment, the varnish layers showed visible changements. The films of resins, initially transparent, turned to yellow. Under ultraviolet light, they were now characterized by an intense yellow-green fluorescence, while fresh films did not give fluorescence.

Fig. 3 Surface of a mock-up after the accelerated ageing

Fig. 3 Surface of a mock-up after the accelerated ageing

Photographs under visible light (left) and UV light (right).

Credits: ©Rollo 2012.

18On the other hand, the substrates dindn’t show any macroscopic changement. The surfaces under the varnish layers remained white and didn’t show any fluorescence after exposure to UV light.

19The surface of all the mock-ups has been photographed under visible and UV light, using a camera with macro lens (photos of the whole surface) and an optical microscope (for the magnification of specific interior areas), before and after the cleaning tests in order to performe comparative examinations.

20The cross-section analysis of a micro-sample from the surface of one of the mock-ups has also been performed, in order to visualize the thickness of the varnish layer.

21Finally, a plastic film having two rectangular openings measuring 1,5 cm x 2,00 cm has been positioned on the surfaces of all the mock-ups, in order to delimit two areas to clean on each mock-up (A and B).

Application of the gels on the mock-ups

22The application of gels on the mock-ups followed a rigorous scientific protocol, defined from a series of preliminary tests performed on one single mock-up. Small portions of all gels initially formulated (containing four different solvents and characterized by various 80PVA/borax weight ratios) have been tested on the surface for few minutes (up to 10’), after which they have been removed with tweezers and the solubilized varnish taken away with a dry cotton swab. Based on the results, gels for performing tests on all mock-ups have been selected, and the times of application have been defined (tables 1 and 2).

Table 1 Composition of gels applied on the mock-ups

Table 1 Composition of gels applied on the mock-ups

Table 2 List of all the applications

Table 2 List of all the applications

*Two consecutive applications of each gel on the same area

23The procedure required that small portions of gels were modeled on Melinex® with a spatula, until obtaining a thick and homogeneous film with a rectangular shape of  ca. 4 cm2. In this way, they were gently applied on the surfaces of the mock-ups, within the rectangular areas delimited by the plastic film. During the applications, small pieces of absorbent paper have been used in order to absorb the solvent when released out of the cleaning areas.

24At the end of application, each gel has been removed in a single step by tweezers. Next, the swelled and dissolved varnish was taken away from the surface using a cotton swab and without exercising any pressure. All tests have been performed in the same day.

Fig. 4 Application/removal of a gel from the surface of a mock-up

Fig. 4 Application/removal of a gel from the surface of a mock-up

From left to right, up and down: the gel is applied on the surface and removed using tweezers. Dissolved varnish is taken away with a dry cotton swab.

Credits: ©Rollo 2012.

Results and discussion

25Gels containing four organic solvents - isopropanol, ethanol, acetone and metiletilketon- have been initially formulated for this work.Most of them are formed by the 80PVA/borax weight ratio 4/1 (containing the 3 wt % of polymer and the 0,75 wt % of crosslinker) and the organic solvents are incorporated in two different concentrations: 15 wt % and 30 wt % for isopropanol, ethanol, acetone and 10 and 20 wt % for MEK. This remarkable difference in the amount of organic liquids for gels containing the same solvent was functional to investigate the influence of alcohols and ketones on the solubilizing power, as well as on the mechanical properties of the systems.The remaining gels are formed by the 80PVA/borax weight ratio 2/1 (containing the 3 wt % of polymer and the 1,50 wt % of borax). In this case, the same organic solvents are incorporated only at a 15 wt % concentration.

26Modulating the concentration of the 80PVA/borax weight ratio it is possible to vary the amount of structural interconnections of the systems. In this way, gels with different elastic properties and different viscosities are obtained (2 wt % 80PVA/ 1 wt % borax formulations are more “rigid” than the others). The use of systems characterized by different viscoelastic properties was aimed to the study and the comparison of macroscopical behaviours of gels like the application and removal from the surfaces, their potential to be manipulated and their performance in the cleaning action.

27Preliminary tests performed on one single mock-up with all the gels allowed to choose both formulations and times of application on all mock-ups. Gels with the best cleaning performance have been selected (gels A and G, containing the higher weight % respectively of isopropanol and acetone). All the other gels containing the same solvents but with different compositions have been also considered, in order to compare the cleaning performance of all systems containing the same solvent as well as their macroscopic behaviours. For that reason, all the application times should be kept the same.

28Times of application of 2’, 4’ and 10’ have been chosen for gels A, C and G, in order to obtain different results in terms of cleaning, as preliminary tests showed (at 2’ and 4’ a partial removal of the varnish layer occurred, while at 10’ the almost complete cleaning was obtained). Moreover, two consecutives applications of 5’ each on the same area (using a new portion of gel for the second application and removing the solubized varnish ad the end of the first test) have been also considered. The aim was the comparison with the results obtained by the longest single application of the same gel (10’). Applications < 10’ for gels B, H and I have not been considered, because any significant solubilization of the resin occurred at those times during the preliminary tests.

29Based on the results, some first observations concern the solubilizing power and the cleaning performance of the formulations used. The tests performed showed that gels containing the higher amount of organic solvents (gels A, Figures 5 and 6)

Fig. 5 Mock-up n.1 before and after the tests performed with gel A for 2’ (A) and 4’(B)

Fig. 5 Mock-up n.1 before and after the tests performed with gel A for 2’ (A) and 4’(B)

Credits: ©Rollo 2012.

30On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after the cleaning under visible light (up) and UV light (down).

Fig 6 Mock-up n.2 before and after the tests performed with gel A applied for 10’(A) and with two applications of 5’each (B)

Fig 6 Mock-up n.2 before and after the tests performed with gel A applied for 10’(A) and with two applications of 5’each (B)

On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after the cleaning under visible light (up) and UV light (down).

Credits: ©Rollo 2012.

31Gels G were much more performing in dissolving the varnish layer, compared to the other formulations applied for the same times.

Fig. 7 Mock-up n. 3 before and after the tests performed with gel B applied for 10’(A) and with two applications of 5’each (B)

Fig. 7 Mock-up n. 3 before and after the tests performed with gel B applied for 10’(A) and with two applications of 5’each (B)

On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after  the cleaning under visible light (up) and UV light (down).

Credits: ©Rollo 2012.

Fig. 8 Mock-up n.4 before and after the tests performed with gel C for 2’(A) and 4’ (B)

Fig. 8 Mock-up n.4 before and after the tests performed with gel C for 2’(A) and 4’ (B)

On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after cleaning under visible light (up) and UV light (down).

Credits: ©Rollo 2012.

Fig. 9 Mock-up n.5 before and after the tests performed with gel C for 10’(A) and with two applications of 5’each (B)

Fig. 9 Mock-up n.5 before and after the tests performed with gel C for 10’(A) and with two applications of 5’each (B)

On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after cleaning under visible light (up) and UV light (down).

Credits: ©Rollo 2012.

32In particular gels B (Figure 7) and H, containing 15 wt % of solvents and the same 80PVA/borax weight ratio, applied for 2’ and 4’ caused a very superficial and almost imperceptible removal of the varnish. This means, as expected, that the amount of organic liquids heavily influences the solubilizing power of these formulations. Regarding the gels containing 15 wt % of solvents and 80PVA/borax weight ratio 2/1 (gels C and I), they unespectedly were able to better swell and dissolve the varnish layer than gels containing the same solvent content but 80PVA/borax weight ratio 4/1 (gels B and H) and applied for the same times (Figures 7 and 9). Then, a higher content of borax can also influence the solubilizing power of those formulations. Finally, it has been observed for all gels that the cleaning action performed by two consecutives applications of gels for 5’ each was deeper than that performed by a single long application of 10’ (Figures 6 and 9).

33Further observations concern the way in which gels solubilized the varnish and the release of liquids during the application on the samples. Applications of gels A, C and G for longer times (2’, 4’ and 10’) caused a progressive reduction in thickness of the varnish layer (Figures 5, 6, 8 and 9). That indicates a very close relation between the release of solvents, which is gradual, and the time of application on the surface. In most of the cases, but in particular for the applications of gels containing 80PVA/borax weight ratio 2/1 (gels C and I), the gradual removal of the layer caused the permanence of a varnish residue uniformly distributed on the cleaned areas (Figures 8 and 9). In general, the possibility to maintain a thin and homogeneous varnish layer on the pictorial surfaces of artworks after performing the cleaning - if it doesn’t represent a risk for painted layers or it doesn’t prevent the perception of the painted image -could be a real advantage. In fact, in this way the impact of solvents on the original layers could be minimized.

34A phenomenon observed for all gels during the applications on the surface of the mock-ups was the release of solvent along the edges of the gels portions. For gels containing 80PVA/borax weight ratio 4/1 a weak spreading of liquids over the surface occurred at about 2-3 minutes from the beginning of application, while for the 80PVA/borax 2/1 gels it occurs after about 4-5 minutes. This phenomenon is reflected on the results of the tests performed. In fact, areas cleaned with gels A, B, G, H show a regular rectangular shape only in cases of applications for less than 4 minutes (Figure 5), while areas cleaned with gels C and I, containing more borax, showed a regular shape even at the end the longest applications (Figure 9). The release of solvents is clearly connected to the rigidity of gels. Formulations containing 80PVA/borax weight ratio 2/1 allow to hold liquids into their structure for a longer time.

35Last observations concern the potential of the formulations tested to be manipulated, their application/removal from the mock-ups, the contact with the surface and finally their optical properties.

36All gels have been easely modeled and applied by simple instruments, as spatulas and tweezers. Gels containing ketones were more sticky than the others, as well as gels containing more borax were more resistant to the the strains applied. Thanks to their elasticity, all the gels have been successfully peeled-of from the mock-ups.When applied, all gels spread themselves well on the surfaces, coming in an intimate contact with them. During the application, gels gradually turned to yellow because of the varnish that progressively was absorbed by the formulations. Anyway, the transparency of the systems allowed an effective control of the surface during the cleaning.

Tests on two easel paintings

37The 80PVA/borax gels have been also tested on the surfaces of two ancient paintings, in order to evaluate their potentialities in removing the layers of oxidized and yellowed natural varnishes used in past conservation treatments. The first one is an oil-on-canvas painting dating to the XVIII century and representing a portrait of a noble man close to Savoy family. The second one is an oil-on-panel painted by Giulio Francia (bolognese painter of XVI century) representing The Mystic Marriage of S. Catherine. Both pictures belong to the collections of the Museo Civico di Arte Antica of Torino

Fig. 10 Paintings where gels have been tested

Fig. 10 Paintings where gels have been tested

On the left, anonymous painter (XVIII century), portrait of a noble man of the Carcherano di Osasco family. On the right, Giulio Francia (XVI century), The Mystic Marriage of S.Catherine. Images of the paintings in visible light.

Credits: Centro Conservazione e Restauro “La Venaria Reale”, 2011.

38The FT-IR analysis of micro-samples of the varnish layers and the UVF analysis of both paintings have been previously performed to obtain informations about the chemical composition and the distribution of the resinous layers on the artworks, respectively. FT-IR revealed the presence, on both paintings, of coatings of natural resins. The observation under UV light of the pictorial surfaces allowed selecting the areas caracterized by the most homogeneous distribuition of the varnishes, that have been then used for the tests with the gels of 80PVA (it has also been checked that the pictorial layers on these areas were not affected by any lifting or remarkable cracking).

39On both paintings some preliminary tests with gels have been performed. On the oil-on-canvas painting two gels containing different solvents -ethanol and MEK- with the same 30 wt% content and 80PVA/borax weight ratio 4/1, have been tested for few minutes (for up to 6’ for the ethanol gel and to 3’30’’ for the other). On the oil-on-panel painting three gels containing the same solvent - acetone- but at different concentrations of 15 wt % and 30 wt % and characterized by different 80PVA/borax weight ratios, have been also applied for several minutes (up to 4’).

40Based on the results of these first tests, the most performing formulations (those that revealed an effective solubilizing action for short application times) have been tested again on the surface of the paintings at different chromatic areas.

41Application procedure was similar to the one used for the work on the mock-ups: gels were modeled on Melinex®, applied on the surface by the help of a spatula and kept in contact with the varnish for the necessary time. After they were peeled off by tweezers and the solubilized varnish removed with a dry cotton swab.

42Fig.11 Application/removal of a gel from the surface of the painting representing the Mystic Marriage of S.Catherine

Fig.11 Application/removal of a gel from the surface of the painting representing the Mystic Marriage of S.Catherine

From left to right, up and down: the gel is applied on the surface and removed using tweezers. Dissolved varnish is taken away with a dry cotton swab.

Credits: ©Rollo 2012.

43No additional solvent has been applied in after the gel treatement. The control of the cleaning results has been performed with a Wood lamp and with a handheld digital microscope. Figure 12shows the result of the application of a gel containing 30 wt % of acetone and 80PVA/borax weight ratio 4/1 maintained on the surface for 4’.

44Fig.12 Result of the application for 4’of a gel (containing 30 wt % of acetone and 80PVA/borax weight ratio 4/1) on the surface of the painting representing The Mystic Marriage of S.Catherine

Fig.12 Result of the application for 4’of a gel (containing 30 wt % of acetone and 80PVA/borax weight ratio 4/1) on the surface of the painting representing The Mystic Marriage of S.Catherine

From left to right: two macro-photographs under visible light (left) and UV light (right) of the cleaned area. Micro-photography (OM) referring to the treated surface.

Credits: ©Rollo 2012.

45The varnish has been successfully removed from the surface through the selective and controlled cleaning performed by the gel.

46During these tests the macroscopic behaviour of gels has been evaluated. The gels have proven to be easely manipulated and shaped, making possible to establish an intimate contact with the surface during the application and being easely applicable/removable.

Conclusions

47The assessment of the performance of several 80PVA-borax gels containing different solvents at various concentrations and containing different polymer-crosslinker weight ratios has been made. Formulations have been applied both on several mock-ups prepared with a surface layer of a mastic varnish and on the surface of two ancient oil paintings characterized by layers of non-original natural varnishes.

48The systematic verification of properties and characteristics of those systems allowed to obtain the following results:

  • The gels operate a selective and controlled cleaning action. Using portions of gels preliminary modeled on Melinex® and gently applied on the surface, it was possible to obtain a reduction in thickness of the varnish layer strictly depending on the time of application.

  • Some formulations can have a good solubilizing power towards oxidized varnishes.

  • Gels maintain their transparency during the contact with the painted surfaces. This allowed to better control the cleaning effects on the surfaces.

  • These systems adhere well to the surfaces during the application, showing their ability to adapt their shape to establish an intimate contact with the surface.

  • Small portions of gels can be easily modeled and applied/removed by peeling from the surface, in both cases using simple instruments as spatulas and tweezers.

49For all the above reasons these innovative systems can be considered a valid future tool for the cleaning of artworks. However, a greater attention to the issue of the release of solvents on the edges of the portion of gels during the application should be paid in following studies.

Haut de page

Bibliographie

CAMPANI, E., CASOLI, A., CREMONESI, P., SACCANI, I., SIGNORINI, E. (2007), "L’Uso di Agarosio e Agar per la Preparazione di “Gel Rigidi”", Quaderni CESMAR 7 (n.4), Saonara (Pd), Il Prato.

CARRETTI, E., GRASSI, S., COSSALTER, M. NATALI, I., CAMINATI, G. WEISS, R.G., BAGLIONI, P., DEI, L., (2009) "Poly(vivyl alcohol)-Borate Hydro/Cosolvent Gels: Viscoelastic Properties, Solubilizing Power and  Application to Art Conservation”, Langmuir, 25 (15) : 8656-8662.

CARRETTI, E., NATALI, I., MATARRESE, C., BRACCO, P., WEISS, R.G., (2010) “A new family of high viscosity polymeric dispersions for cleaning easel paintings”, Journal of  Cultural Heritage, 11 : 373-380.

STULIK, D., MILLER, D., KHANJIAN, H, KHANDEKAR, N., WOLBERS, R., CARLSON, J., PETERSEN, W.C., DORGE, V. (ed.), (2004) Solvent Gels for the Cleaning of Works of Art. The Residue Question, Los Angeles, The Getty Conservation Institute.

KHANDEKAR, N., (2000) “A survey of the conservation literature relating to the development of aqueous gel cleaning on painted and varnish surfaces”, Reviews in Conservation, 1 : 10-20

NATALI, I., CARRETTI, E., ANGELOVA, L., BAGLIONI, P., WEISS, R., DEI, L., (2011) “Structural and mechanical properties of “peelable” organo-aqueous dispersions with partially hydrolyzed poly(vinylacetate)-borate networks. Applications to cleaning painted surfaces”, Langmuir, 27 : 13226-13235.

Haut de page

Notes

1  In this work, with the definition of “gel” we refer to the high viscosity polymeric solutions/dispersions where the solvent is trapped into the structure.

2  Balsite® CTS technical data sheet.

3 Tests with free solvents, colorimetry and gravimetry measuremens.

4 Preparation and drying according to the procedure described in literature,Balsite® CTS technical data sheet.

Haut de page

Table des illustrations

Titre Fig. 1 Removal of hydrogels by peeling them off of a glass surface by means of a spatula
Légende On the left a PVA-borax gel. On the right: a PAA gel.
Crédits Credits: Carretti et al., 2009.
URL http://ceroart.revues.org/docannexe/image/3224/img-1.jpg
Fichier image/jpeg, 104k
Titre Fig. 2 Surface of a substrate realized with the mixture of Balsite® and titanium white
Légende Photographs under visible light (left) and UV light (right).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-2.jpg
Fichier image/jpeg, 64k
Titre Fig. 3 Surface of a mock-up after the accelerated ageing
Légende Photographs under visible light (left) and UV light (right).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-3.jpg
Fichier image/jpeg, 784k
Titre Table 1 Composition of gels applied on the mock-ups
URL http://ceroart.revues.org/docannexe/image/3224/img-4.jpg
Fichier image/jpeg, 28k
Titre Table 2 List of all the applications
Légende *Two consecutive applications of each gel on the same area
URL http://ceroart.revues.org/docannexe/image/3224/img-5.jpg
Fichier image/jpeg, 24k
Titre Fig. 4 Application/removal of a gel from the surface of a mock-up
Légende From left to right, up and down: the gel is applied on the surface and removed using tweezers. Dissolved varnish is taken away with a dry cotton swab.
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-6.jpg
Fichier image/jpeg, 80k
Titre Fig. 5 Mock-up n.1 before and after the tests performed with gel A for 2’ (A) and 4’(B)
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-7.jpg
Fichier image/jpeg, 428k
Titre Fig 6 Mock-up n.2 before and after the tests performed with gel A applied for 10’(A) and with two applications of 5’each (B)
Légende On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after the cleaning under visible light (up) and UV light (down).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-8.jpg
Fichier image/jpeg, 436k
Titre Fig. 7 Mock-up n. 3 before and after the tests performed with gel B applied for 10’(A) and with two applications of 5’each (B)
Légende On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after  the cleaning under visible light (up) and UV light (down).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-9.jpg
Fichier image/jpeg, 396k
Titre Fig. 8 Mock-up n.4 before and after the tests performed with gel C for 2’(A) and 4’ (B)
Légende On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after cleaning under visible light (up) and UV light (down).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-10.jpg
Fichier image/jpeg, 360k
Titre Fig. 9 Mock-up n.5 before and after the tests performed with gel C for 10’(A) and with two applications of 5’each (B)
Légende On the left, images before cleaning under visible light (up) and UV light (down). On the right: images after cleaning under visible light (up) and UV light (down).
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-11.jpg
Fichier image/jpeg, 360k
Titre Fig. 10 Paintings where gels have been tested
Légende On the left, anonymous painter (XVIII century), portrait of a noble man of the Carcherano di Osasco family. On the right, Giulio Francia (XVI century), The Mystic Marriage of S.Catherine. Images of the paintings in visible light.
Crédits Credits: Centro Conservazione e Restauro “La Venaria Reale”, 2011.
URL http://ceroart.revues.org/docannexe/image/3224/img-12.jpg
Fichier image/jpeg, 260k
Titre Fig.11 Application/removal of a gel from the surface of the painting representing the Mystic Marriage of S.Catherine
Légende From left to right, up and down: the gel is applied on the surface and removed using tweezers. Dissolved varnish is taken away with a dry cotton swab.
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-13.jpg
Fichier image/jpeg, 212k
Titre Fig.12 Result of the application for 4’of a gel (containing 30 wt % of acetone and 80PVA/borax weight ratio 4/1) on the surface of the painting representing The Mystic Marriage of S.Catherine
Légende From left to right: two macro-photographs under visible light (left) and UV light (right) of the cleaned area. Micro-photography (OM) referring to the treated surface.
Crédits Credits: ©Rollo 2012.
URL http://ceroart.revues.org/docannexe/image/3224/img-14.jpg
Fichier image/jpeg, 358k
Haut de page

Pour citer cet article

Référence électronique

Giulia Rollo, « Testing on mock-ups and on paintings of innovative polymeric gels for surface cleaning », CeROArt [En ligne], 3 | 2013, mis en ligne le 10 mai 2013, consulté le 25 juin 2017. URL : http://ceroart.revues.org/3224

Haut de page

Auteur

Giulia Rollo

Giulia Rollo has obtained a master degree in Conservation and Restoration of Cultural Heritage at the University of Torino & Centro Conservazione e Restauro “La Venaria Reale”, Italy. Her specialities are the restoration of paintings on canvas and panel, wooden polychrome sculpture and wood furnishing. She also has a master degree in Art History received at the University of Roma Tre, Roma, Italy, with a specialization in modern art and museology. Email: rollo.giu@gmail.com

Haut de page

Droits d’auteur

Licence Creative Commons
CeROArt – Conservation, exposition, restauration d'objets d'arts est mis à disposition selon les termes de la licence Creative Commons Attribution - Pas d'Utilisation Commerciale - Pas de Modification 4.0 International.

Haut de page
  • Directory of Open Access Journals
  • Les cahiers de Revues.org