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1. INTRODUCTION
PVAC resins have been used as
a retouching medium in the eld
of conservation since 1935[1].
In 1991, Golden Artists Colors,
Inc. introduced a line of specially
formulated PVAC conservation paints
based on a mixture of AYAA and
AYAC manufactured by the Union
Carbide Corporation[2]. However,
nearly a decade later, the Union
Carbide discontinued the production
of the PVAC AY resins and Golden
ultimately halted production of their
PVA Conservation Colors by 2010.
Abstract
The eld of art conservation has used Polyvinyl acetate PVAC for consolidation and retouching since
the 1930s. Its use as a retouching medium was rst mentioned in a 1935 journal, Technical Studies in
the Field of the Fine Arts, published from 1932-42 by the Fogg Art Museum. PVAC paints were found to
exhibit little or no discoloration upon aging, could be dissolved in a range of solvents including alcohols,
glycol ethers, acetone, and toluene, and could maintain both clarity and reversibility. Hoescht Mowilith
20 and Union Carbide AYAB were the typical PVAC resins used for inpainting. Collaboration between
Golden Artists Colors and painting conservators led to the introduction of Golden’s pre-made PVAC
conservation paints based on a blend of Union Carbide AYAA and AYAC in 1991. Mark Golden also created
custom-made retouching paints for the 1988-1992 treatment of Whistler’s Peacock Room in the Freer
Gallery of Art. Unfortunately, both the Mowilith and Union Carbide resins were discontinued causing
Golden to cease production of the line in 2010. Continued interest in PVAC retouching paints inspired
Golden to collaborate with conservators and conservation scientists to reformulate a new conservation
PVAC RETOUCHING COLORS:
A BRIEF HISTORY AND
INTRODUCTION TO GOLDEN’S
NEWLY FORMULATED PVA
CONSERVATION COLORS
Kristin deGhetaldi (1) | Brian Baade (1) | Joyce Hill Stoner (1)
| Jim Hayes (2) | Samantha Alderson (3)
1. University of Delaware, 18 E. Main St. Old College room 302, Newark, DE, 19716; kdeghetal@yahoo.com; bbaade@udel.edu; jhstoner@udel.edu
2. Golden Artists Colors, Inc.188 Bell Road New Berlin, NY 13411; jhayes@goldenpaints.com
3. American Museum of Natural History, 79th St. and Central Park West, New York, NY 10024; salderson@amnh.org
paint line three years later. After much
testing, the company was once again
able to provide conservators with pre-
made PVAC conservation paints in
2017. This talk will briey outline the
history of PVAC retouching paints and
discuss some of the specic properties
of the new Golden line including
molecular weight, gloss, solubility,
and practical application tips with
examples from the authors’ personal
conservation treatments.
Keywords
PVAC;
Polyvinyl acetate resin;
Inpainting;
Retouching;
Golden PVA colors;
Golden Artists Colors,
Inc.;
AYAA;
AYAC
While conservators have continued
to use leftover reserves of the AY
resin line for retouching purposes, the
pre-made PVA Conservation Colors
offered some distinct benets. In
2013, a renewed collaboration began
between conservators, scientists,
and Golden Artists Colors, Inc. to
re-create the PVAC retouching
paints. Thanks to ongoing research
spearheaded by objects conservator
Samantha Alderson, efforts were
already underway to identify and
evaluate viable replacements for
some of the discontinued AY resins.
Paintings conservators from the
University of Delaware contacted
Alderson and subsequently reached
out to Golden Artists Colors to
explore the possibility of re-creating
a new line of PVAC retouching
paints for the art conservation eld.
This paper will outline some of the
preliminary analytical results from tests
performed on the replacement PVAC
resin. In addition, practical working
characteristics of the retouching paints
will be summarized based on the
treatment of a 17th-century oil on
canvas painting attributed to Pietro da
Cortona and his workshop.
1.1. Historical Use of PVAC
Conservation Paints
In 1935, PVAC homopolymer
resins were rst tested as a
potential medium for retouching by
conservation scientist Rutherford
John Gettens [1]. These initial tests,
performed at the Fogg Art Museum,
were presumably inspired in part by
an article published in a conservation
journal earlier that year which focused
on the use of polyvinyl acetate in
artists’ paints [3]. By the 1950s, PVAC
resin was being used routinely as a
retouching medium, both as a water-
miscible emulsion as well as a simple
solution binder that could be thinned
with organic solvents [4]. In 1959,
conservation scientist Robert L. Feller
and paintings conservator Mario
Modestini began testing a range of
PVAC resins at the National Gallery
of Art in Washington, ultimately
identifying Union Carbide’s AYAB
resin as possessing the most desirable
working properties [5, 6, 7]. As the glass
transition temperature of AYAB was
82 Kristin deGhetaldi | Brian Baade | Joyce Hill Stoner | Jim Hayes | Samantha Alderson 83PVAC Retouching Colors: A brief history and introduction to GOLDEN’s newly formulated PVA Conservation Colors
fairly low (remaining somewhat tacky
at room temperature), Modestini
would often interlayer resins with
higher glass transition temperatures
(e.g. Paraloid B-72) throughout the
inpainting process to effectively seal
areas containing PVA retouching
and prevent the accumulation of
dust [6, 7]. In subsequent decades
PVAC resin gained popularity as a
retouching medium throughout the
conservation community. By the
1980s, however, Union Carbide was
no longer producing AYAB, prompting
scientists and conservators to identify
a replacement material. Conservation
scientist René de la Rie, then head of
the Scientic Research Department at
the National Gallery of Art, suggested
that conservators consider using a
PVAC resin manufactured by the
German company Hoechst. Mowilith
20 possessed a viscosity and refractive
index close to that of AYAB (RI=1.467)
[7, 8]. While some conservators
continued to mix dry pigments
with Mowilith 20 or with leftover
reserves of the discontinued AYAB
resin, other paintings conservators
expressed interest in obtaining pre-
made retouching colors bound in
PVAC resin. Golden began testing
a 50/50 mixture of AYAC (lower
molecular weight than AYAB) and
AYAA (higher molecular weight than
AYAB) and the mixture was found to
possess satisfactory working and aging
properties. A set of colors bound in
this mixture was provided to paintings
conservators Wendy Samet and Dr.
Joyce Hill Stoner for their treatment
of James McNeil Whistler’s Peacock
Room at the Smithsonian Institution’s
Freer Gallery of Art in Washington
DC (the treatment occurred between
1988-1992) and in 1991, Golden
PVA Conservation Colors became
ofcially available for purchase [2].
Nearly a decade later, Samantha
Alderson, objects conservator at the
American Museum of Natural History,
learned that the Union Carbide AY
resins (AYAC, AYAA, AYAF, AYAT)
had been discontinued and that
Hoechst’s Mowilith 20 was no longer
being manufactured. Additionally,
she learned that that some PVAC
substitutes available through certain
art conservation suppliers were
mislabeled [9, 10]. Consequently, Golden
discontinued their PVA Conservation
colors by 2010 as a replacement resin
had not yet been identied.
1.2 Recent Developments in PVAC
Paints Used in Conservation
The PVAC resins that have been
commonly used for retouching
purposes have not been produced
for nearly a decade. As other PVAC
resins from Union Carbide’s AY
line have also become popular for
other uses in conservation (e.g. as
surface coatings, consolidants, etc.),
a collaborative project was begun
by Alderson and her colleagues to
identify potential substitutes for these
resins, the results of which will be
presented in a for thcoming publication
[11]. They began by collecting samples
of PVAC resin in a wide range of
molecular weights from several
current manufacturers. These were
evaluated and compared to samples
of the discontinued Union Carbide
and Hoescht resins. The team used
a variety of analytical instruments to
evaluate and test the potential resins
including Fourier Transform Infrared
Spectroscopy (FTIR) to characterize
chemical composition and Gel
Permeation Chromotagraphy (GPC)
to measure the molecular weight.
In 2013, Alderson was contacted
by Kristin deGhetaldi, a paintings
conservator, about possible
replacement resins for the re-
formulation of the Golden PVA
Conservation Colors. DeGhetaldi
had been contracted to conserve
a large 12-by-20 foot oil-on-canvas
painting attributed to Pietro da
Cortona in collaboration with fellow
paintings conservator Brian Baade.
Rather than trying to replicate the
original 50/50 mixture of two PVAC
resins of different molecular weight,
Alderson suggested initially testing
single resins as replacements. She
provided Jim Hayes, the technical
director at Golden Artists Colors,
Inc., with ve samples of resins that
seemed to be promising substitutes
for the original mixture as well as
old samples of AYAA and AYAC for
comparative testing.
2. MATERIALS AND METHODS
2.1 Mechanical, Solubility, and
Color/Gloss Testing
Golden’s technical staff produced
ve paint samples based on the
potential resin replacements identied
by Alderson and her colleagues in
addition to re-creating the original 1:1
AYAA/AYAC mixture for comparison.
Each of the ve resins as well as the
1:1 AYAA/AYAC mixture (designated
as the control) were mixed with
three pigments: titanium white
(PW6), quinacridone red (mixture of
PR 206 and PR 202), and raw umber
(PBr7). Paint drawdowns (10 mL)
were created and then subjected to a
series of tests before and after short-
term light aging. Articial aging was
performed under ambient conditions
using a ltered Xenon arc-source
with a radiant exposure of 510 kJ/m2
at 340 nm for a period of 405 hours.
To assess changes in gloss, a BYK
Micro-TRI-Gloss Meter was used
on all paint samples (readings were
obtained at 60 degrees). Resolubility
was assessed by applying cotton
swabs saturated in denatured alcohol
to the surface of the aged paints, and
the number of circles were recorded
before the swabs effectively broke
through the surface of the paint
samples. Flexibility was assessed by
manually manipulating the substrate
(acrylic-primed canvas) in order to
observe any potential cracking, aking,
or delamination. Finally, a Xrite CI7800
Benchtop Color Spectrophotometer
was used to monitor any potential
shifts in color (calculated using the
CIELab delta E masstones).
2.2 Gel Permeation
Chromatography (GPC)
Gel Permeation Chromatography
(GPC) was performed on four
pigmented samples bound in the
nal selected resin: Prussian Blue (PB
15:1/PV 23/PBk 9), Titanium White
(PW6), Yellow Ochre (PY43), and
Burnt Umber (PBr7). All four samples
were prepared by adding 1.5 mL of
tetrahydrofuran to approximately 10-
20 mg of paint. After centrifuging the
samples for 30 seconds, the dissolved
resin was obtained from each of the
samples using a 220 nm lter. 5 µl
of each samples was then injected
into a Waters Alliance® System
2695 Separations Module equipped
with a Waters 2414 Refractive
Index Detector using a 300x7.8mm
High Speed GPC Column (25
minutes @ 35 deg C). Results were
interpreted using Millenium® 32
Chromatography Manager Software.
3. RESULTS AND DISCUSSION
Golden prepared all ve of the
samples and sent them to painting
conservators deGhetaldi, Baade, and
Stoner to perform a series of blind
tests to determine which had the
most appropriate working properties
(the paints were labelled with a code
so that the conservators would not
know which resin they were using).
The conservators unanimously
concluded that they could not tell the
difference between the workability
and re-solubility of the ve samples
from that of the original Golden PVA
Conservation Colors (1:1 AYAA/
AYAC). With the analytical and
empirical testing completed, Alderson
suggested that Golden select Vinavil
Raviex BL5S as their PVAC binder
as her research found that this resin
possessed physical properties that
were most like Mowilith 20 [11].
84 Kristin deGhetaldi | Brian Baade | Joyce Hill Stoner | Jim Hayes | Samantha Alderson 85PVAC Retouching Colors: A brief history and introduction to GOLDEN’s newly formulated PVA Conservation Colors
3.1 Mechanical, Solubility, and Color/
Gloss Test Results
Golden’s initial tests on Vinavil Raviex
BL5S have yielded promising results when
compared to the control (1:1 AYAA/
AYAC). It showed minimal differences
from the control when subjected to
the same series of tests (see Tables 1A
and 1B) both before and after short-
term aging. The Vinvavil Raviex BL5S
even slightly outperformed the control
on some tests. For example, the delta
E values measured for each of the new
PVAC colors before and after light aging
were all below one (not discernible to
the human eye). Very minimal changes
in re-solubliity were also observed, an
expected outcome as PVAC resins have
shown little to no signs of cross-linking
over time.
3.2 GPC Molecular Weight Results
Five samples were subjected to
GPC analysis in order to conrm the
molecular weight distribution that has
been reported in the literature and by
the relevant manufacturer (see Figure
1). Samples of AYAF, AYAA, and AYAC
were chosen as they span a wide
molecular weight range and the latter
two resins were used as the primary
binders for Golden’s previous PVA line.
Two paint samples were also run: burnt
umber (PBr7) bound in 1:1 AYAA/
AYAC and cadmium red light (PR
108) bound in Vinavil Raviex BL5S. As
some of the samples did not generate
narrow distributed single peaks, only an
approximation of Vinvavil’s molecular
weight could be calculated. Based on the
logarithmic relationship between the
elution time and molecular weight, the
weight average molecular (as opposed
to the number average molecular) was
calculated to be approximately 33,000
amu. When comparing this value to
the reported molecular weight range
(22,000-30,000 amu), this falls in line
with the trend observed for all three
AY resins, as AYAF, AYAA, and AYAC
all possess weight average molecular
values that are greater than their
number average molecular values
[8, 12]. Additional testing using GPC
and Size Exclusion Chromatography
(SEC) will likely reveal more precise
approximations for both the weight
average molecular and number average
molecular values.
3.3 Working Properties of PVAC
Retouching Paints
Like the earlier PVAC AY resins, the
new line of Golden PVA Conservation
colors (made with the replacement
resin Vinavil Raviex BL5S) can be
dissolved for retouching purposes using
alcohols. To slow down the evaporation
rate (allowing for more blending
and richer glazes), a small amount of
ethylene glycol or propylene glycol
monomethyl ether (e.g. Arcosolv PM)
can be added to the alcohol diluent.
To achieve a more matte appearance,
the PVA colors can be further thinned
with alcohols (e.g. ethanol) or mixed
with additions of dry pigment and/
or matting agents (e.g. glass micro-
balloons). Conversely, a thicker and/
or more glossy paint consistency can
be achieved by increasing the amount
of ethylene glycol/ propylene glycol
monomethyl ether. Additions of the
pure resin (Vinavil Raviex BL5S) pre-
dissolved in an alcohol, a mixture of
alcohol and ethylene glycol/propylene
glycol monomethyl ether, or pure
ethylene glycol/ propylene glycol
monomethyl ether can be added to
the paint. All of these factors can be
controlled to achieve the desired level
of gloss and open working time.
One advantage of using the pre-made
PVAC conservation paints is that the
colors are well and evenly dispersed.
One challenge that faces conservators
who hand-mixing dry pigments into
a fast-setting resinous medium is to
create a paint that will not “sink” over
time, a phenomenon due in part to
poor pigment dispersion. One potential
drawback to all PVA retouching paints
is the low refractive index of the resin
(1.4665). This is easily remedied by the
superimposition of a glaze containing
a higher refractive index (e.g. Laropal
A81) or the application of a surface
varnish with similar properties. PVAC
resins are polar by nature and therefore
do not wet well onto pigments that
are non-polar such as carbon black
[13]. One solution to counteract this
problem is to add minute amounts
of alcohol soluble dyes (e.g. Orasol®
Dyes) that have satisfactory lightfast
ratings; however, the dyes should be
used sparingly and preventive measures
(e.g. coating with a varnish containing
UV Light Stabilizers, employing
appropriate lighting conditions) should
be considered if dyes are added to the
paints. This particular method (using
the newly formulated PVA paints) was
used to reintegrate large sections of
paint loss on The Triumph of David in
order to achieve a satisfactory degree
of saturation in darker passages (Figure
2). Like some of the AY resins, the glass
transition temperature of the resin
in the new PVAC paints is close to
room temperature (the manufacturer
recommends storing the pure resin at
a temperature above 20 degrees C).
Consequently, it is advisable to coat the
retouching paints with an appropriate
varnish layer possessing a higher glass
PIGMENT BINDER GLOSS
(BEFORE XENON AGING)
GLOSS
(AFTER XENON AGING) INITIAL FLEXIBILITY FLEXIBILITY
(AFTER XENON AGING)
Titanium White Control (1:1 AYAA/AYAC) 26 24 control 0.4
Vinavil Raviex BL5S 48 46 Slightly less 0.57
Quina-cridone
Crimson
Control (1:1 AYAA/AYAC) 24 34 control 1.05
Vinavil Raviex BL5S 32 34 Slightly more exible 0.97
Raw
Umber
Control (1:1 AYAA/AYAC) 5 5.4 control 0.5
Vinavil Raviex BL5S 8.1 10.3 Slightly more exible 0.76
Table 1A • Chart summarizing test results relating to gloss and exibility of PVA paints before and after short-term aging.
PIGMENT BINDER INITIAL RESOLUBILITY RESOLUBILITY
(AFTER XENON AGING)
CIELAB, ∆E, MASSTONES
(AFTER XENON AGING)
Titanium White Control (1:1 AYAA/AYAC) 27 45 0.4
Vinavil Raviex BL5S 22 29 0.57
Quinacri
-done Crimson
Control (1:1 AYAA/AYAC) 40 54 1.05
Vinavil Raviex BL5S 25 28 0.97
Raw
Umber
Control (1:1 AYAA/AYAC) 42 45 0.5
Vinavil Raviex BL5S 37 39 0.76
Table 1B • Chart summarizing test results relating to resolubility and color change of PVA paints before and after short-term aging.
Figure 1 • Comparison of chromatograms collected using GPC associated with AYAF, AYAA, AYAC and
original and new PVA paint samples.
86 Kristin deGhetaldi | Brian Baade | Joyce Hill Stoner | Jim Hayes | Samantha Alderson 87PVAC Retouching Colors: A brief history and introduction to GOLDEN’s newly formulated PVA Conservation Colors
transition temperature in order to
avoid the potential accumulation of
dust/grime (although this is likely only
to affect areas that are covered with
thick applications of the paints) [12].
For removal of the paints, ethanol can
be used; however, if the artwork is
sensitive to alcohols, toluene has been
successfully used to remove PVAC
resins after short and long-term aging.
4. CONCLUSIONS
Previous research and studies have
shown that PVAC resins are an
appropriate option for making paints
for use in inpainting. PVAC resins have
been shown to exhibit little or no
discoloration upon aging, are soluble in
a wide range of solvents, and maintain
both clarity and reversibility. The loss of
earlier sources of such a resin prompted
the discontinuation of Golden PVA
Conservation Colors. Research began
to nd a new replacement resin, which
would possess similar or superior
properties and allow Golden to
resume the production of pre-made
PVAC conservations paints. Extensive
testing by scientists and conservators
resulted in the selection of Vinvavil
Raviex BL5S as a replacement resin.
Golden Artists Colors has relaunched
their PVA Conservation Colors and
they are now available to conservators.
ACKNOWLEDGMENTS
The authors would like to
acknowledge Rachel Modrovsky for
her assistance with the preliminary
tests performed on the Vinavil Raviex
BL5S paints. We are also indebted to
Dr. Shuang Liu for performing Gel
Permeation Chromatography on the
PVA samples at the Microscopy and
Mechanical Testing (MMT) Center at
the University of Delaware.
REFERENCES
[1] GETTENS, Rutherford J. - Polymerized vinyl
acetate and related compounds in the restoration
of objects of art. Technical Studies in the Field of
Fine Arts. Vol. 4, no. 1 (1935), pp. 15–27.
[2] STONER, Joyce Hill. - America’s colormen:
Bocour, Levison, Gamblin, and Golden. In
Modern Art, New Museums: Contributions
to the Bilbao Congress, 13–17 September
2004. London: International Institute for
Conservation, 2004. pp. 189–192.
[3] CLARKE, William J.; IVES, Herbet Eugene
- The use of polymerized vinyl acetate as an
artist’s medium. Technical Studies in the Field of
Fine Arts. Vol. 4, no. 2 (1935), p.4.
[4] DIGNEY-PEER, Shawn, et al. The imitative
retouching of easel paintings. In STONER,
Joyce H.; RUSHFIELD, Rebecca A., eds. – The
Conservation of Easel Paintings. London:
Routledge, Taylor & Francis Group, 2012. pp.
607-634.
[5] FELLER, R. - Exposure Tests on Traditional
and Polyvinylacetate Retouching Systems
and Characterization of Certain Modern
Figure 2 • Before (left) and after (right) retouching large area of loss in The Triumph of David attributed to Pietro da Cortona using the newly formulated Golden
PVA Paints combined with Orasol Dyes (photo courtesy of Villanova University).
Proprietary Painting Media. AIC Preprints,
Fourth Annual Meeting, Dearborn, Michigan,
1976, p. 126.
[6] BERGER, Gustav Adolf. - Inpainting using
PVA medium. In Cleaning, Retouching and
Coatings: Technology and Practice for Easel
Paintings and Polychrome Sculpture, Preprints
of the Contributions to the Brussels Congress,
3–7 September 1990. London: International
Institute for Conservation, 1990, pp. 150-155.
[7] BERGER, Gustav Adolf. - Inpainting using
PVA medium – Inpainting using PVA Medium:
Mario Modestini’s Pioneering Research – In
BERGER, Gustav Adolf; RUSSELL, William H.
ed. - Conservation of Paintings: Research and
Innovations. London: Archetype Publications.,
Ltd., 2000. pp. 191–216.
[8] UNION CARBIDE. - Polyvinyl acetate
resins for coatings and adhesives. Danbury,
CT: Union Carbide Chemicals and Plastics
Company Inc., 1989.
[9] ALDERSON, S. - Union Carbide no longer
manufacturing PVAC resins. AIC News Vol. 34,
no. 2 (2009), pp. 16–17.
[10] ALDERSON, S. - Response to Supplier for
AYAA Sought, Conservation DistList. Available
at: http://www.cool.conservation-us.org/
byform/mailing-lists/cdl/2013/0918.html
(12 July, 2017).
[11] ALDERSON, S., DOWN, J.L., MAINES,
C.S., WILLIAMS, R.S., and YOUNG, G.R. -
Substitutes for discontinued poly(vinyl acetate)
resins used in conservation (forthcoming
publication in the Journal of the American
Institute for Conservation).
[12] VINAVIL - Technical data sheet. Raviex
BL 5S. Available at: http://www.vinavil.com/
public/1/SchedeTecniche/raviflex%20bl%20
5s%20-%20a%20(engl).pdf (12 July, 2017).
[13] DIGNEY-PEER, S., THOMAS, K., PERRY,
R., TOWNSEND, J., and GRITT, S. - The imitative
retouching of easel paintings. In STONER,
Joyce H.; RUSHFIELD, Rebecca A., eds. – The
Conservation of Easel Paintings. London:
Routledge, Taylor & Francis Group, 2012. pp.
607-634.
ACADEMY OF ARTS, UNIVERSITY OF SPLIT
20th | 21st OCTOBER 2017
POSTPRINTS RECH 4 | CROATIA
4TH INTERNATIONAL MEETING
ON RETOUCHING OF CULTURAL HERITAGE,
RECH 4
2 3
The Organizing Committee would like to acknowledge the contribution of the
the contribution of the members of the Advisory and Scientic Committees
who made the selection of the communications and posters for the Meeting.
We gratefully acknowledge the nancial support and sponsorship of the
Ministry of Science and Education of Croatia, the Ministry of Culture of the
Republic of Croatia, the University of Split and the Split Student Centre. Special
thanks goes to the Tourist board of Split, the City Museum of Split and the City
of Split for their support in organising the social program of the Meeting. We
express our gratitude to Split University Library and the Faculty of Chemical
Engineering and Technology for enabling us with the conference venue. We
would also like to thank the Split Department for Conservation for providing
us with the workshop materials. Special thanks goes to RETES.HR print centre
and OPG Mateo Curić. We also express our gratitude to Gabriela Rocha and
FabLab Lisboa (Portugal) and to Escola Artística e Prossional Árvore (Porto,
Portugal) for providing us with the conference badges.
ACKNOWLEDGEMENTS
4th International Meeting on Retouching of Cultural Heritage, RECH4
Host Venue | Academy of Arts, University of Split
Title | POSTPRINTS RECH4 CROATIA
Editorial Coordinators | Ana Bailão, Sandra Sustic
Graphic Design | INEDITAR | Cristina Dordio
Abstracts Proofreading | Graham McMaster
Venue and Date | Split, Croatia, 2017
ISBN | 978-953-6617-42-5
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