gini, who continued it

from 1880 to 1889; and

Allyn Cox, who completed it in 1953 (see

chapter 11.) All three

artists worked in true

fresco, although each

artist executed his section in a slightly different

technique and style, presenting an unusual conservation problem (see

foldout).

The frieze begins 58 feet above the floor, in a shallow

cove 8 feet 3 inches high and slightly over 303 feet in circumference. The Rotunda to this height is composed of

the original masonry walls built in the 1820s with brick

and rubble fill. The structure behind and above the

frieze, begun in 1856, is brick and cast iron. 

It was clear, even before inspection at close range was

possible, that the frieze was in serious need of conservation. Leaking rainwater had left unsightly streaks and

white deposits on several areas as early as the 1880s. A

photograph published in 1902, only twenty-five years

after Brumidi began painting, showed that almost onethird of the existing frieze had already been streaked and

marred by extensive leaks (fig. 14–2). Several areas were

disfigured by white patches, thought to be salts transported by moisture in the plaster. Documented recurrence of leaks in certain locations prompted growing concern. Recently, in 1994, the gutter system was modified

to prevent future damage. 

Once the scaffold was in place, the problems could be

assessed more fully. So heavy had the infiltration been at

rumidi’s frieze and

canopy in the Rotunda were the two

most challenging and dramatic of the fresco conservation projects undertaken

in the Capitol in recent

years (fig. 14–1). This

conservation makes a full

appreciation of Brumidi’s

artistic techniques and

achievement possible. The

intent of this chapter has

been to make complex restoration processes understandable, including the kind of research and debate that is

necessary in professional conservation, with technical information included in the notes for those who are interested in more detail. The illustrations provide samples of

the kinds of photographic documentation and diagrams

that are included in the full conservation reports.

The Frieze

Executed between 1877 and 1953, the frieze on the belt

at the base of the dome in the Capitol Rotunda incorporates the work of three artists: Constantino Brumidi, who

began it in 1877 and worked until 1880; Filippo Costag187

CHAPTER 14

Conserving the Rotunda Frescoes

BERNARD RABIN AND CONSTANCE S. SILVER

B

Fig. 14–1. Bernard Rabin inpainting losses. The conservators

used archival photographs to guide the reconstruction of damaged

forms. The water-based paint they used can be easily removed if so

desired in the future.

Fig. 14–2. Early photograph showing water damage to the

frieze. Major leaks had disfigured “Colonization of New England”

and other scenes by the end of the century.

From Glenn Brown, History of the United States Capitol, 1902.
times that both the paint and the surface of the plaster

had been etched, probably because the first leaks had occurred before the fresco had thoroughly cured. Fortunately, we found that the plaster remained well adhered

to the wall of the cove. However, we saw considerable deterioration of the painted surface, indicative not only of

water but also of some inherent weaknesses in the techniques of execution, of ill-advised human interventions,

and of ambient agents (fig. 14–3). 

For reasons not clearly understood, the brown pigment

of the background, especially in Brumidi’s sections, was

powdering or poorly bonded to the intonaco, the top coat

of plaster. In other frescoes in the Capitol, such earth

tones, made of naturally occurring minerals, also suffer

from this lack of adhesion. We also observed two unusual

features of the paints Brumidi and Costaggini had used.

Many areas that should have been white highlights were

rather gray, while other areas, primarily in the dark shadows, had become milky. We hypothesized that the gray

areas were actually details applied a secco after the plaster

was dry, with lead white in oil paints. When used on plaster, lead white can darken over time. We also hypothesized that the milky areas in the dark paints were dark oil

paints applied to the dry fresco, which had cracked and

turned opaque in the presence of water.

To understand the composition of the frieze, we removed fourteen small samples for laboratory analysis.1

The results confirmed our hypotheses. The frieze was basically executed in a true fresco technique with a limited

but characteristic palette composed of earth pigments,

such as naturally occurring iron oxides. However, as we

suspected, some details were added after the plaster was

dry. Lead white in an oil medium was identified in the

now gray highlights, and oil paint was found in many of

the painted shadows. Visually, it was clear that the a secco

details are integral to the composition and consistent with

the artists’ styles and not elements added by a later restorer. An additional cause of discoloration discovered

only during the course of treatment was a gray deposit on

the surface of the fresco. Historical research confirmed

that from 1866 to 1906 the dome had been lighted by

1,083 gas jets, some of which were placed directly under

the frieze.2 The gray deposit was very likely a residue

from the burning coal gas, which contains sulfur pollutants and deposits a particularly tenacious and potentially

damaging grime.

In addition to these problems, we saw that some alterations were made in 1953 by Allyn Cox when he cleaned

and overpainted parts of the frieze prior to executing the

final three sections. He correctly assessed that the frescoes

had become obscured by grime and that it would be illadvised to match the final three sections to darkened adjacent surfaces. Although not a trained conservator, Cox

carried out a remarkably safe cleaning method, and he left

188

Fig. 14–3. Diagram showing the deterioration of the

painted surface of “Oglethorpe and the Indians.” Before

conservation treatment was begun, existing conditions were

carefully recorded. 

Etching Streaks











































































 























































































































































189

CONSERVING THE ROTUNDA FRESCOES

Fig. 14–4. Group of Native Americans in “Oglethorpe and

the Indians” shown before conservation. In badly damaged

areas, Allyn Cox used his imagination to reconstruct forms. 

Fig. 14–5. Group of Native Americans in “Oglethorpe and

the Indians” shown after conservation. The professional

conservators consulted historic photographs of the frieze for accuracy.
a detailed report of the methods and materials he used.

Cox cleaned the fresco with water, which removed considerable surface grime. However, he was not able to remove

the tenacious oily gray deposit, which visually obscured

and weakened the precise relationship of dark shadows

and light highlights that make the frieze appear to be

three-dimensional. To compensate for this, he reinforced

many of the darks and lights. He also repainted the brown

background completely and created his own details in

areas where the fresco was badly damaged. He sprayed

areas of flaking paint with a casein medium in an effort to

stabilize them, but this consolidant apparently contracted

over time, adding to the instability of the fresco. 

Treatment

One of our primary objectives was the physical conservation

of the frieze, such as the stabilization of the flaking surface.

Removal of accretions was equally important for the frieze

to be legible both as a pictorial narrative and as an integral

component of the Rotunda’s interior architecture. Our

treatment had to incorporate cleaning methods that were

effective and safe for the work of each artist and to maintain

harmony and continuity from section to section. These

goals were complicated by the three distinct artistic styles

and the varying aging properties of the materials.

We learned as we worked our way around the frieze,

and we stopped to reassess after the treatment of the first

five scenes. We began by removing heavy surface dust

with a soft brush. The figurative areas were then cleaned

with water and the highlights were further cleaned with a

special dry, eraser-like Wishab sponge. Cox’s repainted

brown background was left in place, but streaks and uneven areas were feathered and blended with gouache,

high-quality poster paint to which an acrylic emulsion

was added to provide binding strength. This served to

consolidate and make the background less sensitive to any

future leaks. Stains, discolorations, and losses in the figurative areas were inpainted with reversible acrylic paints. 

As discussed above, we learned that the fresco did not

look as bright as we had expected because the oily gray

deposit from the old gaslights remained on the surface.

Cleaning tests proved that highly diluted aqueous ammonium hydroxide, gently applied through Japanese tissue,

could safely remove the deposit. Care was taken to ensure

uniformity from section to section. After conserving the

whole frieze, we returned to Brumidi’s first five sections

and treated them with this cleaning method to ensure visual continuity. 

We were successful in removing Cox’s casein-based

overpaint from the figures and from the background. Although streaked and abraded in some areas, the original

paint was generally intact. The lighter tone of the original

brown background and its many natural irregularities actually enhance the trompe l’oeil effect, making the cove

appear more realistically as a three-dimensional architectural surface. The deeply etched streaks in the brown

background were inpainted in high-quality poster paint

with added acrylic medium.

Extensive reconstruction was required only at scene 10

(see fig. 14–3). Here Cox had reconstructed some damaged areas by extrapolating from the fragmentary forms

that remained (fig. 14–4). By consulting archival photographs, we were able to restore more correctly Brumidi’s original details (fig. 14–5). 

The disfiguring efflorescence in some areas, particularly

in scene 16, proved to be calcium sulphate dihydrate, a

soluble salt, which caused some loss of paint and friable

190

Fig. 14–6. Detail of face in “Pizarro Going to Peru.”

Brumidi’s use of impasto white highlights gives the frieze an added

sense of depth. Photo: Rabin & Krueger.
called puntini and spolvero, which produce dotted lines

(see chapter 3), especially in areas with complex elements

such as the intricate Aztec calendar. He generally painted

the heads and hands, the most complex and expressive

components of the body, on individual giornate. Transfer

techniques are less numerous on the bodies. Close examination reveals the work of a secure and spontaneous artist,

who boldly painted shadows and highlights (fig. 14–6).

Both technically and artistically, Costaggini departed

from Brumidi’s richer and more spontaneous Baroque

style and sculptural approach. His plaster is smoother,

mixed with less sand. Costaggini’s style is linear, detailed,

and rather hard-edged, the pigment thinly applied on a

very white, smooth, and rather brittle plaster.

Costaggini also relied heavily on a variety of transfer

technique—incisions, puntini, and spolvero—to ensure

the precise and somewhat rigid execution of a myriad of

details. Thus his giornate tend to be rather large and predictable, most probably laid out in precise relationship to

the cartoons (fig. 14–7). 

In the final three sections of the frieze, Cox imitated

Costaggini’s more illustrative style. His intonaco is quite

smooth; his giornate are large and predictable in form.

Cox used the spolvero technique of transfer. To create an

appropriate backdrop for the Wright brothers’ airplane he

reconstructed as clouds the first element of Brumidi’s

composition, a mountain intended to be at the end of the

scene showing the Gold Rush. 

plaster. We softened and removed the deposits with

water, consolidated the plaster, and inpainted the small

areas of loss.

At scene 16, Costaggini’s final section, and at scene

17, Cox’s first section, the scaffold was placed so that

the frescoes of both artists could be examined and

treated simultaneously to evaluate the contrast between

the nineteenth- and twentieth-century frescoes after

cleaning. We concluded that Cox had executed his three

scenes in tones that are somewhat darker and grayer

than Brumidi’s and Costaggini’s frescoes because he had

matched his paints to the appearance of the nineteenthcentury frescoes as obscured by the grimy gray film. Removal of heavy dust from Cox’s section and a modified

cleaning of Costaggini’s final figures produced a harmonious transition. 

Discovery

Brumidi’s sections are executed in a classic high Baroque

technique. The plaster is rough and sandy; the pigments,

with additional lime, applied in a noticeable impasto.

Brumidi also employed transfer techniques that had become common in the Renaissance and Baroque periods in

Europe. Nail holes, some with nails still in them, indicate

where he had tacked his cartoons to incise outlines in the

damp intonaco. He employed the transfer techniques

191

CONSERVING THE ROTUNDA FRESCOES

Fig. 14–7. Diagram of the giornate in “William Penn and

the Indians.” The number and configuration of the sections of

plaster on which Brumidi painted each day were recorded as part of

the conservation treatment. In this section, Brumidi’s small sections

to the left contrast with Costaggini’s larger ones to the right.
192

Fig. 14–8. First area on the canopy cleaned. Bernard Rabin

is dwarfed by Freedom, whose vibrant colors were uncovered

beneath heavy layers of grime.
We hypothesized that the deterioration was caused by

fluctuations in humidity, pollutants from the gas jets,

and moisture that may have collected in the past at the

base of the dome. Documentation indicated that the

condition of the dome and the interior climate of the

Rotunda had been unstable from the beginning. As early

as 1870, the dome required constant maintenance to

prevent corrosion and leaks.5 Until approximately 1940,

when the clerestory was sealed during the installation of

air conditioning, the base of the dome remained open,

exposing the fresco, especially its lower registers, to extreme changes in temperature and humidity. During the

conservation project, temperature and humidity were

monitored and found to be generally stable, thanks to

the air conditioning.

During the conservation treatment, we analyzed Brumidi’s working methods by recording and studying the

giornate that we identified (fig. 14–9). Brumidi transferred his full-size cartoons to the wet plaster by incising

the outlines of the figures. As in the frieze, many holes

from the tacks or nails he used to hold the paper can still

be seen at close range. In some areas, we could tell by the

way the plaster overlapped which section was done first. A

fresco painter logically begins at the top of the composition and works to the bottom to avoid damage to and

drips on finished sections. Brumidi started near the apex

of the canopy, above the face of George Washington. At

first his giornate were small and consistent, with divisions

occurring right at the figures so that he had adequate

time to paint all of the details while the plaster was still

curing. At the lower edge of the canopy, as the figures

themselves became larger, and, perhaps in a rush to finish,

the giornate became larger, the quality of the drawing

and painting broader and less detailed. The poor adhesion of the pigment could have been caused by the plaster

having cured too much before it was applied. Brumidi’s

technique of transferring his cartoons also changed from

incisions to pounces. 

The central circular section of plaster at the apex appears to have been inserted after the surrounding areas

were completed; it overlaps the other sections with

ragged edges, and its color does not exactly match the adjacent areas. One of the last giornate reworked outlines a

figure removed from the grouping of “Commerce,” now

known to have been a portrait of Montgomery C. Meigs.

At Meigs’s request, his face was partially scraped off and

painted over, but its location is still slightly visible. Brumidi signed and dated the fresco 1865 at the bottom of

this group (see fig. 9–19). 

The many dark lines around the giornate appeared inconsistent with what we knew of the fresco tradition and

of Brumidi’s other work. Typically, it would be the

artist’s intent to have the joins between giornate appear

Once the conservation treatment was completed, the

work of the three artists appeared to be an integrated

whole, and Brumidi’s intended illusion of relief sculpture

in light and shade was greatly enhanced. In addition to

knowing that all loose areas were consolidated and damage correctly repaired, we had gained a new appreciation

of Brumidi’s skillful technique and mastery of form.

The Canopy

The Capitol Rotunda is a magnificent symbolic space for

which Brumidi’s canopy fresco is the climax, demonstrating his mastery in merging monument with monumental

art. Viewed today after conservation, the dome is alive

with color, movement, and drama. Before treatment,

however, darkening from grime, disfiguring heavy dark

lines between the sections of plaster, extensive overpainting, and inconsistencies in the fresco’s surface destroyed

the intended effect of three-dimensional space. Thus,

conservation was a high priority. 

Facing us was a complex web of possibly interrelated

factors, including the mechanical structure of the canopy,

variations in technique or materials, alterations made by

the artist, accretions of dirt and grime, and the effects of

cleaning and restoration work carried out by Allyn Cox in

1959. Archival research, scientific testing, examination of

current conditions, and the conservation skills of our

team all contributed to the comprehensive treatment program. Work began in July 1987 once the enormous scaffold was constructed. 

The first step was to carry out cleaning tests. The

amount of grime darkening the fresco was even greater

than we expected. Even with the first simple water cleaning, the sky changed from dark gray to yellow white (fig.

14–8). As on the frieze, we found a layer of tenacious

grime from the burning of the coal-gas jets that illuminated the dome for forty years.

To identify possible mechanical causes for the fresco’s

deterioration, we studied the structure of the dome. The

canopy, which provides the fresco’s structural support,

consists of a curved framework holding cast-iron laths

suspended from the cast-iron structure of the outer

dome. A core sample showed that the first rough plaster

coat (arriccio) was pushed between the slots, creating a

wedgelike plug that holds the plaster in place. This rough

coat has sand of large particle size and at least three types

of fibrous fillers to enhance its tensile strength.3 Analysis

of the finer top coat (intonaco) confirmed that Brumidi

used the traditional true fresco mixture of lime and sand

in a 1:3 ratio.4 The composition of the plaster appeared

to be consistent and therefore not a cause for the deterioration of the painted surface in the lower areas.

193

CONSERVING THE ROTUNDA FRESCOES
invisible. Before the treatment began, archival research

was undertaken to compile graphic and written records

that might provide evidence of Brumidi’s original intentions for the fresco and of its appearance as actually

painted. This research encompassed the artist’s original

oil sketches, correspondence, and reports (as described in

chapters 9 and 10). We also relied on maintenance

records for the Capitol and Allyn Cox’s report on his

work in 1959.6

Brumidi’s final oil sketch (see fig. 10–5) shows that he

intended an expansive atmospheric sky at the top of the

canopy. Archival photographs from 1866, 1881, and

1904 confirm his fidelity to this design, although some

dark lines at the giornate, especially in the central sky,

194

Fig. 14–9. Diagram of the giornate in the canopy. The

conservators discovered that Brumidi painted the Apotheosis of

Washington on 120 sections of plaster.
This last work will cover the connections of the

pieces of plaster, put up in sections at every day, and

giving more union to the colors at the said junctions,

for obtain the artistic effect. 

It is general rule in doing this kind of work to

avoid the damp atmosfere [sic] of the winter season,

but I will do this last finish as soon as the weather

will permit, early in the spring, as alway [sic] I have

done in every other painting in real fresco in the

Capitol, and everywere [sic].7

Two entries from the annual reports of the Architect,

one year apart, further confirm Brumidi’s intention to

minimize the visibility of the joins between the giornate:

(1865) The picture over the eye of the dome is all

painted in, but the artist is unwilling to have the scaffolding removed until the plastering is thoroughly dry,

and the picture toned. As it will be at times viewed by

were already evident in the earliest photograph (see fig.

9–14). During the treatment, we observed that Brumidi

attempted to tone or blend the lines between giornate in

some places (fig. 14–10). In other places, he may have

channeled the joins out in preparation for filing them

later. These observations are consistent with the artist’s

letters and the Architect of the Capitol’s annual reports,

which reveal that Brumidi intended the giornate to be invisible and that he planned to blend them further.

Brumidi wrote on September 19, 1865, to Architect of

the Capitol Edward Clark:

. . . I am working at present the last group, and for

the next week I have finish to put in color every figure upon the fresh mortar. 

That remain to do for the completion of it will require only five, or six weeks, but must do it in the

proper time, when the mortar will be perfectly dry,

and the colors do not any more changement.

195

CONSERVING THE ROTUNDA FRESCOES

Fig. 14–10. Brumidi’s hatch marks. The artist tried to reduce

the prominence of some of the joins by scratching lines across them

in the plaster. Photo: Rabin & Krueger.
gas-light, he wishes to have the opportunity of trying

it by this light before dismissing it from his hands.8

(1866) Although the fresco picture over the eye of the

dome has been exposed to view by taking away the

scaffolding, it is not finished, as the artist intends to

soften down the harshness at the joinings of the plastering. He was under the impression that these imperfections would disappear when the surface became

dry. He holds himself in readiness to do the proper

toning and blending whenever the scaffolding is in

place for the painting of the vault of the rotundo.9

As explained in chapter 9, Brumidi was never provided

a scaffold in order to do this work. By 1904, the giornate

had become even more visible throughout the fresco (fig.

14–11). Photographs taken after the 1959 restoration

offer a radically changed image. The giornate lines in the

central sky had been painted out, thus appearing lighter

at first, but they subsequently darkened even more with

time. In addition, a sun, darker yellow than the sky, occupied the apex (fig. 14–12).

The archival and visual evidence clearly showed that

Brumidi did not intend the giornate to be dark and ob196

Fig. 14–11. The Apotheosis at the turn of the century. Over

time, grime accumulating in the joins made the giornate more

prominent. Photo: Detroit Photographic Co., 1904.
colors were mixed to match those darkened by grime.

Where he found Brumidi’s paint to be flaking and the plaster in the central section friable, Cox brushed off the loose

material and repainted areas as he thought best, evidently

without reference to archival photographs. Fortunately, the

overpaint he used was water soluble, rather than oil-based,

and he left a detailed written report of the steps he took.

As we have seen, tests showed that the plaster remained

perfectly adhered to the structure of the canopy, but Brumidi’s pigments were not adhered in some places, a condition not normally found on true frescoes. 

trusive. High-magnification examination of samples taken

from the dark joins between the giornate provided further confirmation. They showed four distinct layers: the

intonaco, Brumidi’s frescoed pigment layer, Brumidi’s retouching, and Cox’s 1959 overpaint.10

Allyn Cox was a muralist, not a trained conservator. He

did what many painters do best, and that is to paint. No

professional guidelines for conservation existed in his time.

By today’s standards he repainted much more than was

necessary, covering large areas of undamaged original surface. He believed it was not safe to clean the fresco, and his

197

CONSERVING THE ROTUNDA FRESCOES

Fig. 14–12. The Apotheosis before conservation. By 1987, the

forms and colors were dulled by grime, and the paint applied

between the giornate in 1959 had darkened and become extremely

disfiguring.
An important question to resolve was

the medium, if any, in which Brumidi

mixed pigments he applied a secco, that

is, after the plaster was dry, which would

be more fragile than the true fresco. To

answer this question, nine microsamples

of the layers of intonaco and paint were

examined by autofluorescent staining to

test for the presence of proteins, carbohydrates, and oils. Unfortunately, because much of the original fresco had

been sprayed with a casein and lime mixture by Cox in 1959, the samples

showed evidence of protein: casein is derived from milk. It was therefore difficult to draw firm conclusions about Brumidi’s medium.

There were, however, two significant

findings. First, flaking green paint from

one figure untouched in 1959 showed no

evidence of any organic media, suggesting

that Brumidi did not paint any major areas

a secco. In this case, the flaking surface appeared to be due to an inherent flaw in the

fresco technique, possibly because of the

use of an unstable, clay-containing pigment. Second, Brumidi’s paint on the

joins between the giornate gave a positive

test for protein that was distinctly different

in comparison with that for the 1959 overpaint. This is a strong indication that Brumidi toned at least some of the joins a

secco, that is, with an organic binder.

Pigment analysis confirmed Brumidi’s

traditional fresco palette of earth colors,

largely based on hematite, ocher, and

terre verte, with anhydrite white. The

blue is ultramarine, presumably synthetic.

The analysis also revealed in some samples

titanium white, a pigment that was not

commercially available until about 1920, thus clear evidence of areas repainted by Cox in 1959.

Finally, we analyzed the pollutants from the ring of gas

jets, which, combined with moisture, would have been

particularly damaging. The coal gas released large

amounts of particulate matter and incompletely burned

hydrocarbons, which were deposited as a thick and tenacious blue-gray soot on the fresco similar to that found

on the frieze below.11 Sulfur oxides, produced by the

combustion of most hydrocarbon fuels, can produce sulfuric acid in the presence of water, such as condensation.

The resulting sulfuric acid will react with the plaster,

weakening it.12

Armed with these data, we developed a course of treatment. Fragile surface areas were consolidated. The disfiguring surface grime and sooty deposit were removed with

a diluted solution of ammonium bicarbonate after several

cleaning tests were carried out.13 Then Cox’s 1959 overpaint, which had matched the uncleaned fresco, was removed with dampened natural sponges. However, it could

not be cleaned off in areas where removal would damage

Brumidi’s surviving original paint. The restoration also in198

Fig. 14–13. Area where loose plaster had been brushed off.

The conservators found numerous areas, especially in the brown

and green drapery, where little original pigment remained,

leaving white plaster. Photo: Rubin & Krueger.
Most areas were cleaned at least

three times. One of the most dramatic

moments of treatment was the removal of the sun that Cox had mistakenly created at the apex of the

canopy. As we removed the dirt, the

water-soluble dark yellow overpaint

came away as well (fig. 14–14). It was

startling to have the sun disappear.

Our consultant, Paolo Mora, who was

certain that Brumidi’s first section of

plaster at the apex of the dome had

been entirely misinterpreted in the

1959 restoration, looked up and exclaimed, “Ah! At last we see the true

sky.” There is always a thrill of discovery when a conservator uncovers the

original intent of the artist.

With guidance from archival photographs, the damaged areas were inpainted with watercolors (see fig.

14–1). Where passages of original

color proved water-soluble, they

were reintegrated with colored

artist’s chalk, which could be easily

removed if necessary but which

blended well with the fresco. Harmonizing the monumental figures,

which measure up to 16 feet in

height, required that we step back

frequently to gain perspective on our

work. We noticed that Brumidi

slightly elongated the lower part of

his figures so that they would look in

proper proportion when viewed

from below. Each area, and indeed

each figure, had different conservation problems. Some figures, such as

Washington, were almost perfectly

intact. Other areas, such as Victory/Fame’s green drapery, were intact but fragile and could not be completely

cleaned. Where removal of the overpaint was not possible

in the most damaged areas, it was retouched with materials that can be clearly distinguished from the original and

easily removed in the future.14

Visual reintegration was the most challenging problem

of this conservation project because so many figures had

been seriously damaged and inaccurately reconstructed

during the 1959 treatment. Brumidi himself inadvertently complicated our problems because he often deviated from his own incised outlines during the actual

painting of the figures. Consequently, pre-1959 photographs, especially a set located in the photo archives of

volved careful cleaning of the fragments of original surface

in the most damaged areas, which provided the key to

Brumidi’s original colors for the inpainting of these areas

of loss (fig. 14–13). When confronted with Cox’s overpaint of the fragile Brumidi color beneath, we had to

search creatively for a successful cleaning method. By first

applying mineral spirits to the affected areas and then delicately removing the overpaint with water, we were able to

preserve Brumidi’s original work.

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CONSERVING THE ROTUNDA FRESCOES

Fig. 14–14. Apex of the canopy in various stages of

cleaning. The surface of the fresco was cleaned as many as three

times in order to gently remove various types of grime and

overpaint. Here, the false sun is partially removed.
200

Fig. 14–15. “Science” before conservation. The

legibility, three–dimensionality, and beauty of each

scene were marred by dark grime, the darkened

overpaint outlining the giornate, and stiffly repainted

drapery.

Fig. 14–16. “Science” during conservation. Cleaning,

mainly with water, revealed Brumidi’s vibrant colors,

especially in the delicately painted rainbow. The contrast

with the uncleaned areas, at left, was striking.
while reducing the amount of contrast. To achieve this

end, the joins in the light sky areas were slightly

blanched and blended with chalk. As a result, the fresco

can be read as a whole, as Brumidi intended (fig.

14–17). 

Until the scaffold was removed and the fresco viewed

under normal light conditions, we could not be sure that

the retouched and repaired areas would be invisible. To

our gratification, our treatment was successful, and we

were thrilled to see the integrity of the composition was

restored, from the grandeur of the entire composition

(see frontispiece) to the mastery evident in the individual

bold brush strokes (fig. 14–18). 

the National Geographic Society, were invaluable for the

visual reintegration of damaged figures.

As the cleaning progressed, we no longer saw dark

gray skies and muddy colors (fig. 14–15).The fresco became luminous and bright, section by section, layer by

layer (fig. 14–16). Even after inpainting damaged areas,

the lines between the giornate remained aesthetically distracting. However, extensive overpainting of an artist’s

original work, even to cover up his original mistakes and

difficulties, is not an ethical solution. Working with Architect of the Capitol George White and Curator Barbara

Wolanin, we arrived at a balanced approach. Mr. White

suggested we retain the physical evidence of the giornate

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Fig. 14–17. “Science” after conservation. The figures seemed

to come alive after treatment, when the entire fresco regained its

clarity and harmony.
202

Fig. 14–18. Detail of “Science.” A close-up view of the

cleaned fresco leads to an appreciation of the varied types of

hatched strokes Brumidi used to enhance the sense of space and

three-dimensional forms.
and energy dispersive x-ray spectroscopy (EDS). The analyses were carried out by Dr. Robert Koestler in August 1987. 

The elements detected in each layer were as follows: (1) intonaco: Ca,

S, Si, Fe (each less than 5%), Mg (less than 1%); (2) Brumidi pigment

layer: Si, Ca, S, Fe (each less than 5%), Ti (contamination from Cox overpaint); (3) Brumidi’s retouching: Ca, S, Si, Mg (each less than 5%); (4)

Cox’s overpaint: Ca, S, Ti, Mg, Si (each less than 5%), Fe (less than 1%).

11. Color infrared photographs of the surface following cleaning tests

provided some indication of the concentration of sooty accretions that

had become fixed on the fresco. Scanning electron microphotographs of

small samples from the same areas before and after cleaning revealed the

nature of the surface accretion, small particulate matter that is consistent with sooty pollution. Most of this accretion was removed during

the 1987–1988 conservation project. Analyses were carried out by Dr.

Robert Koestler in August 1987. 

12. The corrosive action of sulfuric acid on calcium carbonate (lime)

materials, such as plaster, produces gypsum (calcium sulfate dihydrate).

Gypsum is a soft and water-sensitive material; when found in this manner, it reduces the cohesive strength of the plaster.

13. Fragile areas were consolidated with a brushed application of a 5

percent solution of Acryloid B 72 in toluene. AB 57, which contains

both sodium bicarbonate and ammonium bicarbonate, is a standard

cleaning agent for frescoes. However, during tests on the canopy, it

acted too energetically. The ammonium bicarbonate component provided effective cleaning with controllable action.

14. The unstable and overpainted figures presented several difficulties. The 1959 overpaint could not be left visible because the colors no

longer matched the cleaned adjacent areas of the fresco. However, the

overpaint had become tenaciously attached to and embedded in unstable paint and intonaco. Thus, separation of the overpaint from the original, without causing further damage to surviving original paint, remained a constant and difficult problem.

These areas of unstable and overpainted original paint were treated by

brushing them with mineral spirits, followed by an application of water

and/or a dilute solution of ammonium bicarbonate. The mineral spirits

provided a semi-impervious layer over the original paint, protecting the

original while the overpaint was removed. The mineral spirits evaporated out of the fabric of the fresco. However, in most areas some overpaint was left on the surface, to avoid further abrasion of the surviving

original paint. The overpaint was visually reintegrated with reversible

watercolors and artist’s chalk.

In the most damaged and unstable areas, most of the overpaint was

left intact, gently cleaned with a sable brush and Wishab sponge, and visually reintegrated.

Notes to Chapter 14

1. The analysis was carried out by McCrone Associates in 1986.

2. A vivid description of the gaslight system is provided by Dr. John

B. Ellis, in The Sights and Secrets of the National Capitol (Chicago:

Jones, Junkin & Co., 1869), p. 77:

Descending as we came, we pause in the gallery under the

fresco to notice the ingenious arrangements of the gas-lights.

Four hundred and twenty-five burners are arranged in a circle

around the base of the canopy, at distances of one inch apart,

and over each one passes an incombustible wire connected

with an electrical battery placed between the outer and inner

shells of the dome, near the stairway, on our right as we go

down. . . . A pressure on one of the knobs opens a valve, and

allows the gas to flow up to the burners, and a touch upon an

adjoining knob causes an electric current to flash along the

copper wire over the burners, and in an instant the whole

dome is a blaze of light. The effect of this illumination is very

fine. The light falls brightly over every object, and when seen

from without the dome seems almost on fire.

3. The sample contained two hair-like fibers, apparently horsehair,

and the chaff of grain.

4. X-ray diffraction analyses were carried out by Gregory Cavallo,

American Museum of Natural History, New York City, June 1987.

5. “Such painting as was necessary to keep the joints tight and prevent corrosion has been done, and the inner portion kept clean by laborers paid out of the appropriations for repairs. Some comments have

been made on the continual expenditures of money to keep in repair a

dome made of such indestructible material as iron, but when the expansion and contraction of that material, between heat and cold, is considered, it may be easily understood why constant care and watchfulness is

necessary.” 1870, AOC/AR, p. 5. 

6. Allyn Cox, “Technical Report on the Condition of the Canopy

Fresco in the Rotunda of the National Capitol, and the Restoration

Work Carried out there in 1959.” July 14, 1959, AOC/CO.

7. CB to Edward Clark, September 19, 1865, AOC/CO.

8. Annual Report, Architect of the Capitol Extension, November 1,

1865, p. 5.

9. Ibid., November 1, 1866, p. 2–3.

10. The stratigraphy of the dark joins of the giornate was studied by

the highly sensitive techniques of scanning electron microscopy (SEM)

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