The
scope of work for the conservation treatments of the Rosario Chapel
included previous interventions, which corrected problems with roof
drainage, poor ventilation, and most importantly the 2006 emergency
stabilization of detached plaster on the interior dome and pendentives
that greatly improved the overall condition of the chapel's plaster and
murals. In 2008, treatments were carried out to
stabalize the mural paintings using a system of grouting of the
detached areas of the murals. The treatment testing was primarily
focused on the conservation of the first decorative scheme and the
treatment of later campaigns focused on the removal of fragmented
vignettes by strappo
technique. Before the conservation treatments could be implemented, a
flexible light weight bracing system was developed and fabricated to
support areas during injection. A support system also had to allow for
positive pressure to be applied after the grout or adhesive was
injected to guarantee bonding to both the masonry and the plaster.
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The
treatment goals of the 2008 pilot conservation treatment program were
as follows:
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1. Expose the original painting campaign by
removing layers of limewashes and overpaints;
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2. Consolidate the chalking original paint;
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3. Determine the rate of treatment in situ per
square foot; and,
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4. Test strappo removal techniques of the later painting fragments. |
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Since
there were several different types of deterioration which had to be
addressed during the course of treatments, ACL developed conservation
treatments specific to each type of detachment. Originally, it was
anticipated that the primary deterioration was the detachment of the enfoscado
layer or scratch coat of plaster from the masonry substrate with voids
large enough to inject the grouting formula. These areas existed
primarily around areas of major loss and were generally large enough to
accept grout. There were also areas of the murals where the enlucido, or finish
coat of plaster, was detaching from the enfoscado and
detachment within the enfoscado
itself. These areas also occurred around major areas of loss. Around
the areas of major loss, the enfoscado
fails as fragments or is friable, and the enlucido
layer requires grouting to the masonry substrate. If the enfoscado was
sound, the area between the enlucido
and enfoscado
was grouted. These
areas are generally large enough to accept grout and the grouting
protocol is implemented as described. |
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Example of bulk and thin limewash and
residual lime haze accumulations
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All
of the revealed original painting was consolidated with a 5%
B72/acetone (w/v) solution. The solution was applied through a barrier
of wet-strenth tissue. Additional consolidants were applied in areas
where pigment was not consolidated by a first application.
Consolidation also visually mitigated any remaining lime haze by
changing the refractive index of the surface rendering the haze
invisible.
Although the arches and sanctuary were not originally included in the
scope of work, there appeared to be several areas that needed
attention and treatment until a conditions survey could be conducted.
Areas that were determined to be extremely fragile and the threat of
loss was eminent were treated using the standard grouting and adhesive
injection protocol with facings applied where necessary. |
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Lower
pendentive after treatment |
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Bracing
system used during the implementation of grout and acrylic
adhesive injections
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Conservation treatment drawing
for the dome |
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Conservation treatment drawing
for pendentive 1 |
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Through
various tests it was established that dry mechanical cleaning was the
most effective method for removing the bulk limewash layers and for
mitigating the lime haze. When thin, well-adhered limewashes were
especially difficult to remove, it was helpful to soften the lime with
water either by spray, compress, or poultice application (depending on
substrate condition) prior to picking or scraping the material with a scalpel and brushes. Strappo
did
successfully remove bulk limewash that was in contact with the glue but
it required additional mechanical removal and was both more time
consuming and expensive than simply using hand tools. Testing of strappo
methods, however, was very helpful for its potential use in removing fragmented
vignettes of later painting campaigns. The most desirable matte paint
consolidation results were achieved with a 5% solution of Paraloid B72
in acetone. |
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Before
and after paint removal on area on north chapel wall, inner arch
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The strappo removal
was very successful in areas that were attached to bulk limewash layers
at the top of the pendentive. Powdered pigment without any substrate was
lifted from a large plaster repair in the center of the pendentive (the
plaster repair was left in place because the removal of it without
appropriate shoring would put the extant original mural at risk for
total loss). |
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Applying
gauze and colleta glue as part of strappo removal for the SW pendentive
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Detailed
cleaning was a much more labor-intensive and time consuming process
that included cleaning thin, well-adhered liimewash layers as well as
the bluish-gray lime haze from painted and plain plaster surfaces. When
limewashes were extremely difficult to remove, the surface was wet
with water (usually by spray delivery) and softened material was
mechanically removed. Alternatively, the surface was wet by compress or
poltice if overspray was a concern. |
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Thin
limewash removal with poultice |
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| Southwest
Pendentive, before treatment
Southwest
Pendentive, during treatment
Southwest Pendentive, after treatment, CLS 2008 |
| As of 2008, the interior murals of Rosario Chapel
have been stabalized and the fragments of the later murals were
carefully removed and stored with the Archdiocese. The fate of what may
be the oldest extant church murals in Puerto Rico remain in the hands
of the Archdiocese. | | | | | | | |
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