Rome, restoration work started on St. Peter's Baldachin

Work has begun in St . Peter’s Basilica on the restoration of the Baldachin of St. Peter. Last week, the preliminary works were presented to the press, and four centuries after the beginning of the construction of the imposing monument by Gian Lorenzo Bernini (Naples, 1598 - Rome, 1680), built between 1624 and 1635 on the commission of Pope Urban VIII, the work site has begun, and now the Baldachin has been appearing, for a few days, concealed by scaffolding. It is, engineer Alberto Capitanucci, head of the technical area of the Fabbrica di San Pietro, explained to Vatican News, “a large construction site of a large work, and it is so both from the point of view of its historical meaning, but also in terms of its size. It is like a ten-story building, 30 meters high from the basement to the cross. The first step of the work, which began today, is the approach with the provisional works to the surfaces being restored. The scaffolding has already reached two-thirds of the total height and wraps around, without touching, the entire perimeter of the Baldachin.”

The choice was made, Capitanucci said, “to create and keep free space for the practicability of the papal altar, to allow for the year’s services. All papal celebrations that are normally held in the Basilica will have a way to continue to be there. Once this is finished, the second phase will begin, which is the completion on the entire surface on the parts that were not accessible to date for the calibration survey of the restoration work.” At the moment, the altar and steps have been covered with wooden boards to allow liturgical celebrations even during the restoration. “Finally,” the engineer concluded, “on all the scaffolding support points there is obviously a distribution and balance system, let’s say footing, made of wood, which is the softest material and thus protects the flooring from possible stresses.”

Before any work begins, a detailed graphic and photographic documentation of the Baldachin (already partly completed) will be carried out in order to preserve a record of its current state. During the execution of the work, each phase of the intervention will be scrupulously documented. Upon completion, a comprehensive photographic campaign will be carried out to record the final state after restoration. As a standard practice, each part of the Baldachin will be subject to careful graphic documentation in three distinct stages: initially, a descriptive report of the current condition of deterioration (for all visible parts) will be prepared. During the work, details of ongoing interventions will be recorded, and at the end, a final documentation will be made, which may highlight particular details of the workings, construction techniques, and materials used. All information gathered will be illustrated through graphic bases processed from photographs. The scientific investigations will be conducted in several stages under the supervision of the Cabinet of Scientific Research Applied to the Cultural Heritage of the Vatican Museums.

Initially, the focus will be on the state of conservation and degradation phenomena. During the work, investigations will focus on the type of interventions to be carried out, while in the conclusion, detailed information will be collected on the techniques of execution and the materials used. In the initial phase, patina samples will also be taken in different areas sufficient for in-depth analysis on their composition, aimed at understanding the phenomena of degradation. In the final phase, alloy and possibly wood samples will be taken for targeted investigations, considering that all surfaces will be clean and easily inspected.

The restoration will concern both the metal surfaces (bronze and iron), the stone surfaces (the column bases are in fact made of masonry and covered with precious marbles, namely Carrara white, Aquitaine black, and Egyptian alabaster), and the wooden structure.

As for metal surfaces, the most appropriate methods for cleaning bronze usually involve mechanical techniques that focus on manual operations. Tools such as scalpels, hand brushes with fine iron bristles, microdrills with small grinding wheels or abrasive rubbers, steel metal bristles, vibro-incisors, acoustic scalers, and other similar tools are used, which allow the removal of corrosion layers without completely eliminating them, ensuring satisfactory aesthetic results. These methods make it possible to carefully check the surfaces of the object area by area during the work process. However, in the case of the canopy, since the metal surfaces are relatively well preserved, the proposed approach will be significantly different. It will mainly be necessary to remove deposited dirt, of various kinds, using solvents, compresses or other methods, without affecting the original patinas or gilding. The goal will be to rid the partially burnished and partially gilded bronze of the layers of contamination that compromise its appearance and tarnish its original splendor. Several tests will be conducted to identify the most suitable method, and the work will be done manually by highly skilled restorers, inch by inch.

Conservation treatments for the bronze will include the following steps: Washing with normal water followed by deionized water; Application of a corrosion inhibitor; Application of a surface protective layer in several passes. Conservation treatments for iron will be divided as follows: Mechanical surface cleaning to remove inconsistent corrosion products; Washing with normal water followed by deionized water; Application of a corrosion inhibitor and rust converter; Application of a surface protective layer. Upon completion of cleaning and conservation treatment, and after application of the protective, if necessary, touch-ups will be performed to balance the color tone using epoxy paints and additions of small gaps will be made with colored resin.

As for the stone surfaces, the columns have undergone continuous maintenance over the centuries and do not present significant criticalities. However, it is necessary to clean the layers of dust and especially yellowed waxes that compromise the crystalline whiteness of Carrara marble. Particular attention will be paid, if necessary, to the reattachment of the thin slabs of precious alabaster, used as a background to the coats of arms in cases where there are detachments from the white marble-supported lining.

The operations to be carried out include: Survey of the state of preservation, signs of workmanship and finish on the surface of the stone, with provision of site mapping, based on pre-existing survey, divided into categories; Removal of incoherent dust, layered on the surface, through the use of soft brushes and small vacuum cleaners; Removal of deposits partially adhering to the surface and surface stains with tissue packs and deionized water; Inspection of all surfaces for detached parts of the modeling and possible preventive removal; Cleaning of the surface with removal of adhering deposits by application of ion exchange resins; Refinishing of cleaning with removal of wax stains, oil or residues of old protective agents, using selected solvents after appropriate solubility tests; Final finishing stage for removal of residues of compact and adhering deposits, using manual mechanical means and ultrasonic equipment; Removal of old grout with materials that are not compatible with the stone or that have lost their conservative or aesthetic function; Repointing of flakes, fragments and slabs of limited weight and size through the use of epoxy resin; Grouting with lime mortar and marble dust to repair deep cracks and deficiencies, with the execution of targeted assays for the choice of the most suitable composition in terms of color and grain size; Possible surface protection with microcrystalline wax applied with a brush and pulled with a cloth.

Finally, as far as the restoration of the wooden structure is concerned, it should be remembered that the Baldacchino contains more than 20 percent wood, either painted or gilded for the visible parts or left rough for the structural parts. Wood, which is extremely hygroscopic, is very sensitive to changes in temperature and humidity, and constitutes the most compromised part of the structure, with lesions, detachments, cracks, disconnections, and deformations. This delicate situation requires interventions both from a static point of view, for the structural part, and from an aesthetic point of view, for the visible parts such as the “sky” with the Holy Spirit, which was completely repainted and redecorated in 1758 due to the deterioration of the pictorial film. The conservation treatments of the structure will be divided into the following phases: Assessment and securing of the disconnected or dislodged portions of the upper exterior roof and ceiling/ceiling with the Holy Spirit; Vacuuming of sedimented airborne particulates on all surfaces, followed by preliminary biocide treatment by impregnation; Consolidation of the degraded areas of the wood through impregnation of acrylic resin; Consolidation of the cracked wooden elements and reattachment of the protected parts; Disassembly and reassembly of disconnected applique elements, with correction and reinforcement of the support systems; Structural restoration of cracks, sealing and reconstruction of missing parts along the frame; Plastic reconstruction of small lacunose portions of wooden modeling; Second biocide treatment by impregnation; These interventions aim to preserve and consolidate the structure of the canopy, safeguarding its integrity and historical-artistic value.

Photo: St.’s Papal Basilica

Photo: St.’s Papal Basilica

Photo: St.’s Papal Basilica

Photo: Papal Basilica of St.’s

Surface conservation treatments will be carried out according to the following steps: Verification of the nature of the binder used in the drafts of the chromatic backgrounds, by means of solubility tests with increasing polarity; Application of a temporary veiling on the raised portions of the chromatic and gilding backgrounds, using English tissue and cellulose ether for securing; Re-adhesive consolidation of the portions protected by the provisional veiling, through infiltration of microacrylic or organic resins (such as sturgeon glue), with subsequent sealing and restoration to flatness by thermal induction; Unraveling of the treated portions by wet reactivation; Cleaning of the chromatic backgrounds by absorption of sedimented particulates, using English tissue and chelating solution (triammonium citrate), followed by dry rubbing; Removal of any layered repainting on the polychromes and gilding, using solvents selected on the basis of solubility tests, either in direct form or supported by tablets or gels; Brush application of a first coat of saturation varnish, with opaque refractive characteristics; Restoration of depth gaps on the polychromes and gilding by means of impastes of Bologna chalk and rabbit glue, followed by chromatic reintegration with watercolor, tempera or varnish colors, in order to obtain a mimetic agreement with the original field; Chromatic reintegration of the abrasions with visible preparation by tone-lowering, using watercolor and varnish colors; Application by spraying of a final layer of protective varnish, characterized by satin refraction.

The work will last ten months.

Rome, restoration work started on St. Peter's Baldachin

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