NASA/TM— 1999-209435
Recovery of a Charred Painting Using
Atomic Oxygen Treatment
Sharon K. Rutledge and Bruce A. Banks
Glenn Research Center, Cleveland, Ohio
Virgil A. Chichernea
Cleveland State University, Cleveland, Ohio
Prepared for the
12th Triennial Meeting of the International Committee for Conservation
sponsored by the International Council of Museums
Lyon, France, August 29 — September 4, 1999
National Aeronautics and
Space Administration
Glenn Research Center
August 1999
Acknowledgments
The authors would like to thank Mr. Kenneth Be of the Cleveland Museun:\ of Art for providing the painting for
these tests and for his helpful comments, discussion and advice. We v^^ould also like to thank Father Bob Weaver
and the members of St. Alban's Episcopal Church for their helpfulness and enthusiasm surrounding the
restoration of their paintings.
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Aeronautics and Space Administration.
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of changes that may be made before formal publication, this preprint is made
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permission of the author.
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Recovery Of A Charred Painting Using Atomic Oxygen Treatment
Sharon K. Rutledge* and Bruce A. Banks
National Aeronautics and Space Administration
Glenn Research Center
Cleveland, Ohio 44135
FAX: 1-216-433-2221
e-mail: sharon.k.rutledge@grc.nasa.gov
Web Site: www.grc.nasa.gov/ www/e pbranch/ephome.htm
Virgil A. Chichernea
Cleveland State University
Cleveland, Ohio 44115
Summary
A noncontact method is described which uses atomic oxygen to remove soot and char from the surface of
a painting. The atomic oxygen was generated by the dissociation of oxygen in low pressure air using radio fre-
quency energy. The treatment, which is an oxidation process, allows control of the amount of material to be
removed. The effectiveness of char removal from half of a fire-damaged oil painting was studied using
reflected light measurements from selected areas of the painting and by visual and photographic observation.
The atomic oxygen was able to effectively remove char and soot from the treated half of the painting. The
remaining loosely bound pigment was lightly sprayed with a mist to replace the binder and then varnish was
reapplied. Caution should be used when treating an untested paint medium using atomic oxygen. A representa-
tive edge or corner should be tested first in order to determine if the process would be safe for the pigments
present. As more testing occurs, a greater knowledge base will be developed as to what types of paints and
varnishes can or cannot be treated using this technique. With the proper precautions, atomic oxygen treatment
does appear to be a technique with great potential for allowing very charred, previously unrestorable art to be
salvaged.
Introduction
Fire in any structure housing an art collection can result in great cultural loss if the art is unrecoverable
by conventional methods due to extensive charring of the surface. Paintings in particular are challenging to
restore because the carbonaceous char of the varnish and binder is usually intermixed with the paint pigments.
It is difficult to remove the char without removing or moving the pigment. A noncontact treatment technique
using atomic oxygen, however, is able to distinguish many paint pigments from char and allow the char to be
selectively removed leaving the pigment on the surface.
Research into using atomic oxygen as a treatment technique started through inquiries made by the Con-
servation Department of the Cleveland Museum of Art as to available NASA technologies that could be used
to remove urethane varnish. Presentation of these results and discussion with conservators from other organiza-
tions led to investigating the technique for removing soot and char from the surface of paintings and other fine
art. Fire damage was believed by conservators to be a problem area that was in need of some additional re-
storative tools.
Although NASA's focus is on research involving improvements in civil aviation and the peaceful explora-
tion of space, an important function of the agency is to take technologies developed for these programs and
make them available for applications on Earth that benefit everyone. That is why techniques to investigate the
effects of atomic oxygen on various spacecraft materials are being studied for potential benefit to the art con-
servation community.
Atomic oxygen is present in the atmosphere surrounding the Earth at altitudes where satellites typically
orbit. It has been shown to react chemically with surface coatings or deposits that contain carbon (Banks, et al.
1988). In the reaction, the carbon is converted to carbon monoxide and some carbon dioxide. Water vapor can
also be a byproduct if hydrocarbons are present. This process can be harmful to a satellite if enough carbon
Author to whom correspondence should be addressed.
NAS A/TM— 1 999-209435
containing materials that are critical to its operation are removed. Due to the importance of understanding the
reaction, and the need to test potential solutions for protecting surfaces from reaction, facilities have been
developed for producing atomic oxygen on Earth (Banks, et a)., 1989). Radio frequency, microwave, or elec-
tron bombardment has been used to dissociate molecular oxygen into atomic oxygen. These atoms can be
either directed at the surface as a gentle flow of gas or the surface can be immersed in the gaseous atomic
oxygen. Large area exposure is typically performed in a vacuum chamber where pressures range from 0.001 to
100 mtorr depending on the technique used. Smaller areas can be treated at atmospheric pressure using a DC
arc device described in a publication by Banks, et al. (1998). Because the process is dry and the reaction is
confined to the surface, there is less risk of damaging the underlying paint or canvas.
The atomic oxygen cleaning technique has been demonstrated to be effective at removing soot from can-
vas, acrylic gesso, unvarnished oil paint and varnished oil paint. (Rutledge, et a!., 1996; Rutledge, et al.,
1998). This paper investigates its usefulness in removing char from a varnished oil painting. The process,
which has been patented by NASA, is not intended to be a replacement for conventional techniques, but to be
an additional tool for use where conventional techniques may not be effective (US Patent #5560781, 1996).
Procedure
Description of the Painting
The Cleveland Museum of Art donated the charred varnished oil painting used for testing of the treatment
process. It was originally displayed in St. Alban's Epi.scopal Church in Cleveland until an arson fire destroyed
the church in June of 1989. The museum received a pair of paintings from the church for restoration. The sub-
ject of this testing was a painting depicting a female saint with upraised head and eyes. The painting was
heavily soot covered with extensive charring and blistering of the full thickness of the paint. Charring was evi-
dent as a very black and brittle layer. The other painting of the pair, which depicted the Madonna, infant and a
third figure which is probably a young John the Baptist, experienced much less blistering and charring. Resto-
ration attempts were made on the latter painting at the Cleveland Museum of Art using acetone. Methylene
chloride was also tried. These processes removed some of the soot and varnish, however, the surface was still
very dark and features were difficult to distinguish. Both paintings were considered to be unsalvageable and
were donated to NASA for testing of the atomic oxygen treatment process. Because there was less surface
charring, the painting depicting the Madonna and infant was treated first (Rutledge et al. 1998). Success with
this painting led to the attempt to try to remove the much more extensive charring from the surface of the sec-
ond painting, which we named the Saint Painting.
Atomic Oxygen Cleaning
Cleaning of the painting was performed inside a large vacuum chamber that can accommodate a painting
of -1.5 by 2.1 m in size. The vacuum in the chamber is provided by conventional vacuum pumps with pres-
sures during treatment, which range from 1 to 5 mtorr. Two large aluminum parallel plates inside the chamber
produce the atomic oxygen. One plate is connected to a radio frequency power supply operating at 400 W,
while the other plate is at ground potential. The ground plate has several bolts attached to it from which works
of art to be cleaned can be suspended in a vertical position either by attachment of fine wire, or by acting as a
support for a painting stretcher. Canvases too large to fit in the chamber in one dimension, which can be
rolled, could be treated in sections by use of a roll and take-up reel inside the vacuum chamber. Paintings to
be cleaned are suspended so that the ground plate is as close as possible to shield the backside from atomic
oxygen exposure during treatment. A photograph showing a painting mounted inside the chamber is contained
in figure 1. A controlled entry of air into the chamber at rates between -130 and 280 standard cmVmin pro-
vides the source of the oxygen. Radio frequency oscillation of electrons between the two aluminum plates pro-
duces dissociation of the oxygen in the air into atomic oxygen. The radio frequency was generated by a power
supply manufactured by RF Power Products Inc. The dissociation of the air into atomic species creates a pink
colored glow between the plates. The nitrogen in the air has been found not to have an effect on the removal of
carbon and behaves as an inert gas for the treatment exposure. An automated timer and controller on the sys-
tem allows the cleaning to proceed over a desired timeframe unattended and will turn off the system if a loss
in vacuum, water cooling to the pumps and power supply, or drop in plasma intensity is detected.
NASA/TM—l 999-209435
Analysis
A quartz halogen microscope light set at full intensity, with a color temperature of 3200 K (Blackbody
peak wavelength of 900 nm), was mounted on an aluminum beam so that the light could fall on the surface of
the painting at roughly a 45° angle. Quartz halogen was selected as the light source because its spectrum is
closer to that of daylight giving a more balanced source of light across the entire color spectrum than conven-
tional incandescent or fluorescent light. This configuration was used to monitor diffuse reflectance from
selected portions of the painting at various intervals during the cleaning process. The detector was placed near
the light source. The painting was removed from vacuum for these measurements and then returned for further
exposure. The reflectance from a magnesium oxide coated glass slide was used to correct the data from the
detector to eliminate drifts in the intensity of the light source between measurements. The area that could be
illuminated was -1.91 cm in diameter, so it was necessary to select areas from the painting that were both
uniform over this size range and had potential for changing the most (largest contrast) during the cleaning
process. In this way, the end point of the cleaning process could be determined by looking for a leveling off of
the reflected light signal indicating that no further change is taking place.
Results And Discussion
The Saint Painting was -0.733 by 0.58 m in size. A photograph of this oil painting as it was received for
treatment is contained in figure 2. A close-up photograph showing the blistering around the face is contained in
figure 3. Because it is sometimes difficult to get an accurate color match in before and after photographs, it
was decided to restore only half of the painting so that a direct comparison would be available. Two sheets of
0.0127 cm thick polyimide Kapton® manufactured by DuPont were used as a mask over the right half of the
painting. Any type of nonmetallic covering could be used such as cardboard, paper, or some other plastic
sheeting. Kapton® was used because of its availability and its ability to lay in close contact with the surface
(stiff but pliable) without putting excessive pressure on the blisters. These sheets were positioned so that a
portion of the face and the right side of the central figure would not undergo atomic oxygen treatment. The
sheets were wrapped to the backside of the painting and then stapled to the stretcher to hold them in place.
Close contact with the surface was needed to produce a crisp boundary between the treated and untreated
areas of the painting. A photo of the polymer mask covering half of the painting is shown in figure 4.
Prior to treatment, two areas were selected to receive reflected light monitoring at intervals in the treat-
ment process. The center of the forehead was chosen because it should represent a broad area of a light color.
The background next to the halo was chosen because it was believed that this area should remain dark. It was
desired to find two areas that would have the greatest contrast at the conclusion of the treatment and then use
the measure of the contrast as an indicator of the completeness of the treatment. Lacking initial photographs
of the painting, making a determination of the lightness or darkness of particular areas on the painting was
extremely difficult. The soot deposits and char were also not uniform on the surface. This resulted in the clean-
ing of some areas more quickly than other areas. Unfortunately, this was the case for the two areas that were
initially selected. Figure 5 contains the reflectance as a function of cleaning time for the forehead and back-
ground areas. Figure 6 contains a plot of the contrast data, which is the difference in reflectance between the
forehead and background areas. The background did remain dark during the cleaning process as expected, but
the forehead area quickly lightened and then remained fairly constant in refiectance. Other areas of the paint-
ing lightened at different rates. This made it difficult to determine the endpoint through the use of reflected
light from the selected locations. The authors are in the process of testing an alternative technique that scans
the reflected light signal over the entire surface and determines the standard deviation of the signal in order to
give a better indication of the contrast change for the entire painting. For this painting, we had to resort to
judging the endpoint visually.
Figure 7 contains a photograph of the painting with the polymer mask lifted off of the surface after treating
the left half of the painting 10.9 hr with atomic oxygen. At this point, many surface details became much more
visible such as the detail pattern on the sleeve of the robe, the brooch, and the white lace. Further cleaning
removed more of the discolored varnish that appears in the photograph as streaks on the surface of the painting.
Although there were areas where the varnish appeared to have been removed down to the paint after 10.9 hr,
further cleaning did not appear to change the appearance or coloration. At the conclusion of the cleaning, the
paint pigment was loosely bound on the surface. Because the atomic oxygen reaction is confined to the sur-
face, it will remove binder that is in-between and on top of pigment particles but will leave a small amount
underneath that loosely attaches the particle to the surface. This has been observed with early scanning elec-
tron microscope studies of oil paint exposed to atomic oxygen (Rutledge, et al., 1994). Because the
NASA/TM—1 999-209435
allachment point is small, it would be possible to remove pigment by mechanical contact with the surface
such as brushing. Therefore, with the guidance of conservators from the Cleveland Museum of Art, a fine spray
mist of a Grumbacher nonyellowing resin based varnish for oils was applied to fix the pigment on the surface
(See Materials section). After this step was complete, an Acryloid®F-10 based picture varnish (Grumbacher)
was applied by brush to the treated half of the painting. This varnish was selected because the conservators
could remove it if at some future date they desired to complete the restoration by consolidation and in paint-
ing. Figure 8 shows the painting after treatment and revamishing of the left half. Details on this side are clearly
shown and the blistering is much less noticeable although it is still present on the surface.
There is a potential for dehydration shrinkage to occur during the treatment process due to the fact that it
is performed under a partial vacuum. For this painting, there was no deformation observed during treatment. It
appeared that if shrinkage did occur, that the canvas, paint and stretcher shrank at approximately the same
rate because no additional cracking beyond that originally present on the painting was observed after treat-
ment. This may not be the case for every material combination.
The authors were unable to obtain a photograph of the painting before the fire damage occurred so it was
difficult to determine if there were any shifts in paint coloration due to the treatment process. There did not
appear to be any yellowing of the surface. The white lace, whites of the eyes and pearls in the brooch were
white after treatment. There have been a number of oil paints tested for changes in coloration using reflectance
spectroscopy prior to and after exposure to atomic oxygen (Rutledge, et al., 1994). Changes in coloration were
not observed for these materials, however they were more modern paint formulations. Caution must be used
when treating an untested paint medium using atomic oxygen if the cleaning will progress into the paint pig-
ment. A representative edge or corner of the painting which contains most of the paint colors present should be
treated using atomic oxygen with the remainder masked off so that a determination can be made if this process
will be safe for the pigments present. Organic paint pigments will experience oxidation and removal so care
must be taken during cleaning to minimize the loss of organic pigment. As more testing occurs, a greater
knowledge base will be developed as to what types of paints and varnishes can or cannot be treated using this
technique. With the proper precautions, atomic oxygen treatment does appear to be a technique with great
potential for allowing very charred, previously unrestorable art to be salvaged.
Conclusions
Atomic oxygen treatment has been shown to be able to effectively remove char and soot from a fire dam-
aged, varnished oil painting. In order to remove the charred varnish and paint binder, the paint pigment is
exposed. The process leaves the pigment loosely bound on the surface. The pigment can be rebound to the sur-
face using a fine spray mist of a material of the conservator's choice. This can be followed by further treatment
by the conservator. Atomic oxygen treatment can be used to perform extensive cleaning as in this case, or for
a light surface cleaning. It is important to first verify that the materials present in the painting are safe for
atomic oxygen cleaning by cleaning a small representative edge or corner prior to treatment of the entire
painting. This technique appears to have great potential for removing heavy soot and char from the surface of
art damaged during a fire and may be able to allow restoration of previously unrestorable works of art. The
process is not intended to be a replacement for conventional techniques, but as an additional conservation tool
in applications where conventional techniques have not been effective.
References
Banks, B.A., and Rutledge, S.K.: Proceedings of the Fourth European Symposium on Spacecraft Materials in
the Space Environment, CERT, Toulouse, France, Sept. 6-9, 1988, pp. 371-392.
Banks, B.A. et al: Proceedings of the 18'" Annual Symposium on Applied Vacuum Science and Technology,
1989, NASA TM-1 01 971.
Banks B.A., Rutledge, S.K., and Norris, M.J.: An Atmospheric Atomic Oxygen Source for Cleaning Smoke
Damaged Art Objects, Proceedings of the 26'" Annual AIC Meeting, Arlington, Virginia, June 1-7, 1998,
NASA/TM 1998-208506.
Rutledge, S.K., Banks, B.A., and Cales, M.; Atomic Oxygen Treatment for Non-Contact Removal of Organic
Protective Coatings From Painting Surfaces, Materials Issues in Art and Archaeology IV, Materials
Research Society, Cancun, QR Mexico, May 16-20, 1994, NASA TM-106650.
NASA/TM— 1 999-209435
Rutledge, S.K., and Banks, B.A.: Atomic Oxygen Treatment Technique for Removal of Smoke Damage from
Paintings, Proceedings of the Materials Research Society Meeting, Boston, Massachusetts, December 1996,
NASA TM-1 07403.
Rutledge, S.K., et al.: Atomic Oxygen Treatment as a Method of Recovering Smoke Damaged Paintings, Pro-
ceedings of the 26'" Annual AIC Meeting, Arlington, Virginia, June 1-7, 1998, NASA TM 1998-208507.
US Patent #5,560,781; Banks, B.A., and Rutledge, S.K.: Process for Non-Contact Removal of Organic Coat-
ings from the Surface of Paintings, 1996.
Materials
Kapton®polyimide
E.I. DuPont de Nemours & Co. Inc.
1007 S. Market Street
Wilmington, Delaware, 19801 USA
1-302-774-1000
Resin Based Varnish for Oils: N-hexane, Turpentine, Propane, Stoddard Solvent, Isobutane, N-butane
M. Grumbacher Inc.
Bloomsbury, New Jersey 08804 USA
1-908-479-4124
Picture Varnish: D-Limonene 5989-27-5, 2-Ethoxyl Acetate (EEA) 1 1 1-15-9, Rohm & Haas Acryloid® F-10
M. Grumbacher Inc.
Bloomsbury, New Jersey 08804 USA
1-908-479-4124
Figure 1 .—Photograph of the inside of the
vacuum chamber showing the two vertical
aluminum plate electrodes and a painting
hanging on the ground plate (to the right).
NASA/TM— 1 999-209435
Figure 2. — ^The St. Alban's Church
Saint Painting as received from
the Cleveland Museum of Art.
Figure 3. — Close up of the Saint Painting
showing blistering.
NASA/TM— 1999-209435
Figure 4. — ^The Saint Painting with a
polymer mask covering the right half
for comparison purposes to prevent
this side from being treated.
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Cleaning time (hr)
Figure 5. — Plot of the diffuse reflectance of light as a function of cleaning time for the forehead and
background areas of the painting.
NAS A/TM— 1 999-209435
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100 150
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Figure 6.— Plot of the difference in diffuse reflectance of light between the background and forehead
as a function of cleaning time (contrast).
Figure 7.— Photograph of the Saint Painting
after treatment of the left half with atomic
oxygen for 10.9 hours, (mask has been
removed for comparison).
NASA/TM— 1999-209435
Figure 8.— Photograph of the Saint Painting
after atomic oxygen treatment was com-
pleted on the left half and varnish reapplied;
the right half was not treated.
NAS A/TM— 1 999-209435
REPORT DOCUMENTATION PAGE
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1. AGENCY USE ONLY {Leave blank)
REPORT DATE
August 1999
3. REPORT TYPE AND DATES COVERED
Technical Memorandum
4. TITLE AND SUBTITLE
Recovery of a Charred Painting Using Atomic Oxygen Treatment
6. AUTHOR(S)
Sharon K. Rutledge, Bruce A. Banks and Virgil A. Chichernea
5. FUNDING NUMBERS
WU-505-23-2C-00
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
National Aeronautics and.Space Administration
John H. Glenn Research Center at Lewis Field
Cleveland, Ohio 44135-3191
8. PERFORMING ORGANIZATION
REPORT NUMBER
1900
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
National Aeronautics and Space Administration
Washington, DC 20546-0001
10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
NASA TM— 1999-209435
11. SUPPLEMENTARY NOTES
Prepared for the 1 2th Triennial Meeting of the International Committee for Conservation sponsored hy the International
Council of Museums, Lyon, France, August 29 — September 4, 1999. Sharon K. Rutledge and Bruce A. Banks, NASA
Glenn Research Center, Cleveland, Ohio, and Virgil A. Chichernea, Cleveland State University, Cleveland, Ohio 44! 15.
Responsible person, Sharon K. Rutledge, organization code 5480, (216) 433-2219.
12a. DISTRIBUTION/AVAILABILITY STATEMENT
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Subject Category: 27
Distribution: Nonstandard
This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390.
12b. DISTRIBUTION CODE
13. ABSTRACJ (Maximum 200 words)
A noncontact method is described which uses atomic oxygen to remove soot and char from the surface of a painting.
The atomic oxygen was generated by the dissociation of oxygen in low pressure air using radio frequency energy. The
treatment, which is an oxidation process, allows control of the amount of material to be removed. The effectiveness of
char removal from half of a fire-damaged oil painting was studied using reflected light measurements from selected areas
of the painting and by visual and photographic observation. The atomic oxygen was able to effectively remove char and
soot from the treated half of the painting. The remaining loosely bound pigment was lightly sprayed with a mist to replace
the binder and then varnish was reapplied. Caution should be used when treating an untested paint medium using atomic
oxygen. A representative edge or corner should be tested first in order to determine if the process would be safe for the
pigments present. As more testing occurs, a greater knowledge base will be developed as to what types of paints and
varnishes can or cannot be treated using this technique. With the proper precautions, atomic oxygen treatment does
appear to be a technique with great potential for allowing very charred, previously unrestorable art to be salvaged.
14. SUBJECT TERMS
Atomic oxygen; Char; Paintings: Fire damage; Treatment; Cleaning
15. NUMBER OF PAGES
15
16. PRICE CODE
M)!.
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