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San Jose Treatment


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.

The treatment goals of the 2008 pilot conservation treatment program were as follows:

1. Expose the original painting campaign by removing layers of      
    limewashes and overpaints;


2. Consolidate the chalking original paint;

3. Determine the rate of treatment in situ per square foot; and,

4. Test strappo removal techniques of the later painting fragments.

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.
Example of bulk and thin limewash and residual lime haze accumulations
Removing bulk limewash
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.

Lower pendentive after treatment
Bracing system used during the implementation of grout and acrylic adhesive injections
Conservation treatment drawing for the dome
Conservation treatment drawing for pendentive 1
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.
Before and after paint removal on area on north chapel wall, inner arch
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).
Applying gauze and colleta glue as part of strappo removal for the SW pendentive
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.

Thin limewash removal with poultice
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.
TUMA Funding