10.6092/issn.1973-9494/7952
One of the major stages in the conservation and restoration of a painting is to clean its colored surface of unwanted stains, and old and darkened varnishes. Various solvents have been used to date for this purpose; however, new cleaning materials have also come onto the market in the past decade that are still unknown and may never have been employed in Iran. The present study aims to introduce a polymer gel and use an in vitro sample of the substance for cleaning and to then present the results of the tests carried out. Applying a polymer gel in the cleaning of paintings yielded better results and greater advantages over the solvents previously used to clean artworks. The advantages include, performing on the surface without penetrating the lower layers, the absence of residues after application, flexibility, solubility and the gentle removal of old stains and varnishes, maintaining clarity and cleaning the surface by simple removal of the thin dried layer, which requires no mechanical pressure. Microscopic examinations and pH testing showed that this new alternative technique can be of use in cleaning the color layers of oil paintings.
application/pdf
1973-9494
7952
en
Siyamak Alizadeh
Conservation Science in Cultural Heritage
polymer gel
Cleaning and Restoration of an Oil Painting with a Polymer Gel in Iran
Text.Serial.Journal
https://conservation-science.unibo.it/
17
Articles
2018-03-28
2018-03-27
2018-03-28
2019-09-06
139-147
CSCH
Siyamak Alizadeh
2017
10.6092/issn.1973-9494/7952
139
School of Art, Shahid Chamran University, Ahvaz
1973-9494
polymer gel
en
147
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. <em>Langmuir</em>, 25, pp. 8656-8662.
Cleaning and Restoration of an Oil Painting with a Polymer Gel in Iran
https://conservation-science.unibo.it/article/download/7952/7673
17
C    LEANING AND RESTORATION OF AN OIL PAINTING
     WITH A POLYMER GEL IN IRAN

   Siyamak Alizadeh*10
   School of Art, Shahid Chamran University
   Ahvaz, Iran


   Keywords: restoration, conservation, cleaning, oil painting, polymer gel



   1. Introduction

   Imagining a world with no polymer materials is dificult, as these materials have now
become an integral part of our lives and are used in the manufacturing of different
objects, from general everyday tools to complex, medical and scientiic instruments
of precision. Polymer science has also proved advantageous in the conservation and
restoration of historical artworks. The main question examined in this article concerns
the properties of polymer gels used in the cleaning and restoration of paintings, the
techniques they require, and the optimum results expected of them. This study seeks to
present a different application of polymers, that is, the preparation and use of a polymer
gel for the removal of surface layers of stains and unwanted substances accumulated
on the varnishes formerly used on easel and mural paintings as a protective coating in
the restoration of oil paintings. Over time, these coatings undergo physical and chemi-
cal alterations that reduce their reversibility and solubility and change their refractive




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
indices, thus preventing viewers from seeing the true colors used by the painter due
to changes in the pigments. These coatings have other adverse effects too and need
repeated restoration; their elimination from artworks, therefore, appears essential.
   In the proposed gel system, a gel formed by a polymeric compound is used to dis-
solve synthetic and natural substances on the porous surface of paintings. The present
study examines the use of a polymer gel in cleaning stains and varnishes that have lost
their properties. In the past decade, gels have established themselves as a physical
substance used in the conservation of artν Wolbers was the irst to propose the use of
gels for cleaning artworks (oil paintings) [1]. The use of solvents in gel form somewhat
overcomes the adverse effects of using pure organic solvents that deteriorate paint-
ings by penetrating deeply into their layers. Choosing the right solvent and controlling
the cleaning stages are dificult and in many cases, the unwanted layers of material
that have built up on easel and mural paintings present a real challenge. Gels reduce
the capillary penetration of solvents into the layers of an artwork and the gel lattice
keeps solvent evaporation constant. Cleaning with a gel is much easier than cleaning
with any other solvent. The gel cleaning method can therefore be used for the removal
of stains, varnishes and the synthetic polymers that were formerly used on a wide
scale in the restoration of paintings and which are now found to be harmful, in and by
themselves. To further learn about this type of gel and to carry out the study, an ap-

* Corresponding author: s.alizadeh@fsaco.ir

                                                                                             139
                                                                                             plied, descriptive, exploratory method of research was adopted along with the use of
                                                                                             library and experimental instruments and methods of data collection.


                                                                                                2. Background

                                                                                                 In the last thirty years, the application of gels for cleaning has reached its pinnacle.
                                                                                             A new group of organic liquid gels in solid form was identiied in the Department of
                                                                                             Chemistry (CSGI), at the University of Florence, in Italy. In the past ive years, these
                                                                                             new gels have been tested on 16th century triptych paintings and 18th century oil paint-
                                                                                             ings with the purpose of reducing the adverse effects of cleaning on color surfaces; in
                                                                                             both cases, yellowish rotten layers of oil were detected on the canvas. These experi-
                                                                                             ments aimed to assess the applicability of gel systems for cleaning and addressing the
                                                                                             problem of the conservation of old objects. The application of these gels on the paint-
                                                                                             ing samples was done using simple tests. First, a small amount of the prepared gel
S. Alizadeh - Cleaning and restoration of an oil painting with a polymer gel in Iran




                                                                                             (a drop) was applied to the surface for a few minutes and then scraped off by palette
                                                                                             knife. In general, the possibility of keeping the patina formed on the painting surface
                                                                                             and the removal of stains after cleaning can be a real advantage, if this layer of oil is
                                                                                             not harmful to the layers of the painting and does not prevent the real painting from
                                                                                             being read correctly. The preliminary tests [2] were carried out on an 18th century paint-
                                                                                             ing of a nobleman from the Carcherano di Osasco family by an unknown painter and
                                                                                             a 16th century portrait of the symbolic marriage of Saint Catherine. The gel made by
                                                                                             researcher was then tested a second time on paintings with different color hues. Due
                                                                                             to the use of a solvent gel, no other solvent was needed [2].
                                                                                                 The microscopic changes in these gels were assessed during the course of the tests.
                                                                                             The gels were easy to use and malleable, making their close contact with the surface
                                                                                             possible and facilitating their application and removal. Results showed that the gels main-
                                                                                             tained their transparency after contact with the colored surface, therefore enabling better
                                                                                             control of the effects of the cleaning on the surface. A small amount of the gel (a drop) suf-
                                                                                             ices for the cleaning process and is subsequently easily removed by palette knife. These
                                                                                             new cleaning systems provide a valid, new method for cleaning artworks [3].


                                                                                                3. The application and disadvantages of solvents in the restoration of histori-
                                                                                                cal artworks

                                                                                                Solvents are mostly used in restoration tasks such as cleaning coatings (varnishes
                                                                                             used on paintings and degreasing metallic surfaces) and removing organic matter from
                                                                                             textiles. Solvents are also used for the dilution of adhesives and other substances.
                                                                                             The use of a solvent in restoration tasks requires an evaporation rate appropriate to
                                                                                             the painting. In cleaning the surface of a painting with a solvent, rapidly evaporating
                                                                                             solvents (such as Acetone) tend to disappear before softening and removing the oxi-
                                                                                             dized layers of varnish. In contrast, slowly evaporating solvents (such as Glycerin and
                                                                                             Triethanolamine) remain in contact with the main layers of color in the painting for a
                                                                                             prolonged duration and soften them. Under these conditions, mechanical operations
                                                                                             can easily damage the layers of the painting. Another problem with solvents is that
                                                                                             moistened surfaces attract dust. Most solvents are toxic and prolonged and frequent
                                                                                             exposure to their fumes can cause serious harm to the operator’s health. The degree


                                                                                       140
of hazard of a solvent is expressed as its maximum average airborne concentration, or
Threshold Limit Value (TLV), in Parts Per Million (PPM), such that TLV>25 indicates a
relatively high solvent toxicity. Optimum care should be taken when working with sol-
vents, especially in the process of cleaning paintings, when the person is exposed to
the inhalation of solvent fumes for a prolonged period. Flammability is another problem
regarding the use of solvents and ire precautions should be taken to avoid any possi-
ble risk, especially when large amounts of the solvent are being used. Using a volatile
solvent ills the air with the solvent’s fumes and a small spark or the lighting of a match
can cause combustion [4].


   4. Advantages of using the gel prepared by the researcher

   Choosing the right solvent and controlling the stages of cleaning are also dificultν in
many cases, cleaning unwanted layers of coating from easel and mural paintings caus-
es problems [5]. Gels reduce the capillary penetration of solvents into the material lay-
ers of artworks, the gel lattice maintaining solvent evaporation constant. Cleaning with
gels is much easier than cleaning with solvents. The gel cleaning method can therefore
be used for the removal of stains, varnishes and the synthetic polymers that were for-
merly used on a wide scale in the restoration of paintings and which are now found to be
harmful in and by themselves. The surface porosity of paintings has the effect of easily
trapping solvents inside the micro-pores, which makes the cleaning process dificult.
The special formulation of polymer gels is indicative of a major advantage over purely
organic solvents that are still used today for cleaning and removing unwanted layers
from oil paintings. The gel cleaning system has been developed to clean the surface
of historical works of art without causing adverse effects on the artwork. The polymer
gels developed, represent one of the main advances in the cleaning of paintings, as
they leave no negative effects or residues on artworks [6]. Polymer gels can therefore




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
represent a valid alternative in the conservation and restoration of paintings [6]. The
prepared gel contains poly acrylic acid (PAA) compounds [7]. The past few years have
witnessed an increased tendency to use hard gels made from liquid polymer composi-
tions for cleaning artworks. A new group of organic liquid gels in solid form has been
identiied in the Department of Chemistry CSGI, at the University of Florence, in Italy.
Over the past ive years, these new cleaning compounds have been found to be associ-
ated with reduced adverse effects in cleaning on color surfaces [7]. The gels are formed
by a polymeric network of polyvinyl alcohol-co-vinyl acetate and break up copolymers
with different hydrolysis rates in transverse bonding with salt and borax in organic liquid
solvents. These systems have special features, such as high concentration and strong
elasticity; the former affects the spread of cleaning agents on all painted surfaces, and
the latter enables the removal of cleaning agents from the surface, on irst try [6].


   5. Composition

   The gel made by the researcher contains different percentages of different solvents,
including Isopropanol, ethanol, Acetone, polyvinyl alcohol, metiletilketon, Borax (tetra
sodium borate); it is also mixed with epoxy resin, titanium white, cyclohexane and other
materials to produce a solid form. The technical knowledge behind this gel is owned by


                                                                                              141
                                                                                             a company in Iran and its formulation has been patented. This product was prepared
                                                                                             and given to the researcher according to a request made to this company detailing the
                                                                                             gel characteristics [3]. It should be noted that, due to the lack of means for preparation,
                                                                                             this gel was prepared through trial and error and with continuous efforts made by the
                                                                                             collaborating company and at the expense of the researcher involving great dificulties.


                                                                                                6. Application of the gel

                                                                                                 The gel was tested on the sample (an old oil painting named “Qajar Princess” by
                                                                                             an unknown Iranian artist, from the Qajar period), for a duration of 5 and 10 minutes. It
                                                                                             was then removed in a thin layer with no mechanical pressure once it was dried out. It
                                                                                             is possible to reuse the gel once in certain cases. Prior to the application of the gel, it
                                                                                             is necessary to have accurate information about the composition of the paints and the
                                                                                             materials used in the painting. To do this in my workshop, it was not necessary to perform
S. Alizadeh - Cleaning and restoration of an oil painting with a polymer gel in Iran




                                                                                             chemical and physical analyses of the paint because the paints used in the Qajar period
                                                                                             were known and were produced using organic and mineral substances, such as azure,
                                                                                             vermilion, lead etc. The maximum duration for leaving the gel on a painting is 10 minutes,
                                                                                             a longer time has no further positive effects. Two ive-minute applications will produce
                                                                                             better results than a longer 10-minute application. Application of the gel at the recom-
                                                                                             mended duration will reduce harmful oxidized layers of stain and varnish that have lost
                                                                                             their color. Overall, the possibility of preserving the ine uniform patinas on the surface of
                                                                                             the artwork after cleaning is considered a huge advantage. In fact, the application of this
                                                                                             gel makes cleaning a fully controllable procedure. The diffusion of liquids is directly linked
                                                                                             to the hardness and concentration of the gel, and the gel structure of the substance fa-
                                                                                             cilitates the long storage of liquids. This product can be applied to artworks with simple
                                                                                             tools such as a palette knife and, due to its elasticity, it can be successfully removed from
                                                                                             surfaces. It spreads well on surfaces and makes close contact with the surface layer of
                                                                                             the painting. After application, it slowly dries out with little discoloration, since it progres-
                                                                                             sively absorbs the layers of stain and yellowed varnish through its particular composition
                                                                                             and dissolves them. The transparency of this product enables the effective control and
                                                                                             monitoring of the surface of the artworks throughout the cleaning process.


                                                                                                7. Storage of the gel

                                                                                                Considering that this gel is an air-dry product and should not be exposed to direct
                                                                                             light, certain conditions are necessary for its storage. The gel packaging should be air-
                                                                                             tight and protect the product from exposure to light; otherwise it will change color and
                                                                                             lose some of its solvent through exposure to air, consequently losing its effectiveness.
                                                                                             The gel should be kept at room temperature. If all these conditions are met, the gel can
                                                                                             be stored for a maximum of one year.


                                                                                                8. Sample test

                                                                                               The gel was tested on a Qajar-style oil painting on canvas depicting a Qajar prin-
                                                                                             cess and showing yellowed varnish, surface staining and dust (Table 1).


                                                                                       142
   As can be seen in Figure 1, the second test was performed to examine the effect of
the reduced drying time on the outcome of the cleaning. A warm blow-dryer was then
used to accelerate drying time, which caused some peeling of the paint. It was there-
fore concluded that the gel should be allowed a certain time to air dry with no interfer-
ence in order to avoid damage to the colors. The third test was performed to detect
residues. After removing the gel from the painting, a pH test was used to conirm the
absence of residues (Figures 1-3).
   Figure 2 shows the painting depicting the Qajar Princess before the cleaning pro-
cess. Figure 3 A shows the researcher-made gel sample; in Figure 3 B the part of the
painting surrounded by tape is the part used for the test; after applying the researcher-
made gel, we waited for 5 minutes for the gel to dry and then, carefully removed it
(Figure 3 C); Figure 3 D clearly shows the difference between the cleaned part and the
uncleaned parts around it.

Table 1. Sample dimensions.

            Length                           Width                 Wooden frame proile

            60 cm                            40 cm                           2x4 cm




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE




Figure 1. Measuring pH before and after gel application and results for each test.



                                                                                            143
S. Alizadeh - Cleaning and restoration of an oil painting with a polymer gel in Iran




                                                                                             Figure 2. The sample painting depicting a Qajar princess (unknown artist).




                                                                                             Figure 3. A) Using the gel prepared by the researcher for cleaning; B) irst test of the gel for
                                                                                             cleaning painting; C) removing the gel from the surface of the painting after testing on a sample;
                                                                                             D) segments of the painting cleaned with the gel are clearly distinguishable from other segments.


                                                                                       144
   9. Examining the gel residue on artworks

   Residue is a major problem with such compounds, especially solvent gels. The
peel-off property of gels reduces the need for mechanical action on the surface and
cleaning is accomplished without leaving any residue. The cleaning of painting sur-
faces is associated with certain problems, and aesthetic decisions need to be made
with regard to the complete or partial removal of dirt from the varnish and paint layers.
Expert analyses include choosing a technique that facilitates maximum control over
the cleaning process, so that the undesirable layers of oil are removed from the sur-
face without damaging the layers underneath.
   Old cleaning methods involve mechanical cleaning or the use of organic solvents or
liquid alkaline solutions. Some cleaning techniques allow for greater control over the
cleaning process by slowing down evaporation or reducing its spread to other parts.
Art experts use solvent adhesives made of wax and antiques experts use thickening
agents such as wood paste, clay wax and a variety of cellulosic substances.
   The main issue with using gels concerns residues. Any residue remaining on the
clean surface is a potential risk for the artwork, including increased color solubility
or changes in paint composition. The present study examined potential gel residues
on sample paintings selected as a result of a comprehensive study of the subject;
the initial results showed that active substances on the surface break down relatively
quickly. These results were presented at an IIC Melbourne Congress. David Miller, an
art expert and professor of chemistry at California State University Northridge (CSUN),
ran cleaning tests on sample oil paintings at the chemistry lab in his department so as
to determine the amount of residue on the painting surface after cleaning with the gel.
Just as in previous tests, these tests also emphasized the negligibility and the rapid
break-down of residues with the use of the gel cleaning method.




                                                                                                   CONSERVATION SCIENCE IN CULTURAL HERITAGE
   10. Conclusion

   As shown by the studies and practical tests conducted on the sample paintings, the
preparation of polymer gels is a dificult and complex process that is still in its early
stages in Iran. However, the gel prepared in this study did have the cleaning properties
discussed, allowing better control over the operation and facility of use. Moreover, the
amount of dirt stains removed depends on the length of time the gel remains on the
surface. The minimum and maximum times required for this gel are 5 and 10 minutes.
The gel will produce no further positive effects after the maximum 10-minute dura-
tion. Two applications of the gel for a shorter length of time will produce better results
than a single prolonged application. According to the results obtained from the irst
and second samples tested, this gel is well capable of dissolving oxidized varnishes
and maintains its transparency in contact with colored surfaces, thereby enabling bet-
ter control over the cleaning effects of the gel on the surface. A small amount of the
gel can be easily applied to surfaces and then be easily removed using simple tools
such as a palette knife. The resultant cleaning is completely supericial and does not
penetrate the lower layers of the artwork, which is considered an important advantage
of this gel. Furthermore, examining the gel residues after the cleaning process shows
that no further solvents are required to remove the gel itself from the surface, as this
process leaves no residues, making for another advantage in using this technique. The


                                                                                             145
                                                                                             application of this gel reduces art restoration experts’ contact with volatile chemicals
                                                                                             that are physically harmful, and also minimizes any damage to artworks caused by the
                                                                                             use of these chemicals. The storage of this product does not require any special con-
                                                                                             ditions besides room temperature and airtight packaging. The gel can be stored for a
                                                                                             maximum of one year. This cleaning method can be used at the conservator-restorer’s
                                                                                             discretion and with his careful scrutiny, as an alternative or adjunctive method of clean-
                                                                                             ing paintings.


                                                                                                   References

                                                                                             [1]     Wolbers, R.C. (2002). Cleaning painted surfaces: Aqueous methods. London:
                                                                                                     Archetype publications.
                                                                                             [2]     Natali, I., Carretti, E., Angelova, L., Baglioni, P., Weiss, R., Dei, L. (2011). Struc-
                                                                                                     tural and mechanical properties of “peelable” organo-aqueous dispersions with
S. Alizadeh - Cleaning and restoration of an oil painting with a polymer gel in Iran




                                                                                                     partially hydrolyzed poly(vinylacetate)-borate networks: Applications to cleaning
                                                                                                     painted, Langmuir,27, pp. 13226-13235.
                                                                                             [3]     Carretti, E., Natali, I., Matarrese, C., Bracco, P., Weiss, R.G. (2010). Polymeric
                                                                                                     dispersions for cleaning easel paintings: a new family of high viscosity. Journal
                                                                                                     of Cultural Heritage, 11, pp. 373-383.
                                                                                             [4]     Bahadori, R. (2006). Organic chemistry principles and their application in conser-
                                                                                                     vation and restoration of monuments. Tehran: Iran Cultural Heritage Handicrafts
                                                                                                     and Tourism.
                                                                                             [5]     Arnold, A. (1982). Rising damp and saline minerals. In: Proceedings of the 4th
                                                                                                     International Congress on the Deterioration and Preservation of Stone Object,
                                                                                                     Kentucky, 7-9 July, pp. 11-28.
                                                                                             [6]     Giorgi, M., Lenz, S., Rodorico, G., Boglioni, P. (2007). Nanomagnetic sponges
                                                                                                     for the cleaning of works of art. Langmuir, 23, pp. 8681-8685.
                                                                                             [7]     Carretti, E., Grassi, S., Cossalter, M. Natali, I., Caminati, G. Weiss, R.G., Ba-
                                                                                                     glioni, P., Dei, L. (2009). Poly (vivyl alcohol) -Borate Hydro/Cosolvent gels: Vis-
                                                                                                     coelastic properties, solubilizing power and application to art conservation.Lang-
                                                                                                     muir, 25, pp. 8656-8662.


                                                                                                   Biographical notes

                                                                                                Siyamak Alizadeh, born in 1963, is a Faculty member at the Faculty of Art, Sha-
                                                                                             hid Chamran University, Ahvaz, Iran. He is a researcher, teacher, art work restorer,
                                                                                             sketcher, and painter. He has a Ph.D in art research, Tehran University of Art, 2007; an
                                                                                             MA degree in buildings and historical textures repair, Isfahan University of Art, 1995;
                                                                                             Bachelor degree in restoration of ancient artifacts, Isfahan University of Art, 1989; wall
                                                                                             painting preservation and repair course license from Venice European Center, 2004.
                                                                                             He has cooperated with Tehran Museum of Contemporary Art in painting restoration
                                                                                             since 1999. He has taught restoration and art in several university art faculties in Iran,
                                                                                             including Shahid Chamran University, Ahvaz, Iran, since 2010.




                                                                                       146
    Summary
    One of the major stages in the conservation and restoration of a painting is to clean
its colored surface of unwanted stains, and old and darkened varnishes. Various sol-
vents have been used to date for this purpose; however, new cleaning materials have
also come onto the market in the past decade that are still unknown and may never
have been employed in Iran. The present study aims to introduce a polymer gel and
use an in vitro sample of the substance for cleaning and to then present the results of
the tests carried out. Applying a polymer gel in the cleaning of paintings yielded better
results and greater advantages over the solvents previously used to clean artworks.
The advantages include: performing on the surface without penetrating the lower lay-
ers, the absence of residues after application, lexibility, solubility and the gentle re-
moval of old stains and varnishes, maintaining clarity and cleaning the surface by
simple removal of the thin dried layer, which requires no mechanical pressure. Micro-
scopic examinations and pH testing showed that this new alternative technique can be
of use in cleaning the color layers of oil paintings.

    Riassunto
    Una delle fasi principali della conservazione e del restauro di una pittura riguarda
la pulitura supericiale del ilm pittorico con la rimozione delle macchie indesiderate
e delle vernici invecchiate per le quali vengono utilizzati diversi solventi. Tuttavia,
negli ultimi dieci anni nuovi materiali per la pulitura sono entrati sul mercato, ancora
sconosciuti e che potrebbero non essere mai stati impiegati in Iran. Il presente studio
intende introdurre l’uso di un gel polimerico e utilizzare un campione con lo scopo
di effettuare la pulitura, per poi presentare i risultati delle prove. L’applicazione del
gel polimerico durante la fase di pulitura ha dato risultati migliori e maggiori vantaggi
rispetto ai solventi precedentemente utilizzati per le opere d’arte. I vantaggi includo-
no, agendo in supericie senza penetrare gli strati inferiori, l’assenza di residui dopo
l’applicazione, la lessibilità, la solubilità e la leggera rimozione di vecchie macchie e




                                                                                                  CONSERVATION SCIENCE IN CULTURAL HERITAGE
vernici, mantenendo chiarezza e agendo sulla supericie mediante la facile rimozione
degli strati sottili senza richiedere pressione meccanica. Le indagini microscopiche e
il pH test hanno mostrato che questa nuova tecnica alternativa può essere utile per la
pulitura degli strati di colore delle pitture ad olio.




                                                                                            147
