Bonifatius

The initial condition of the painting was characterized by structural ambiguity and aesthetic compromises, resulting from natural ageing, historical devotional use, and poor environmental control. The primary concern involved the composite support, consisting of a paper substrate adhered to a warped wooden panel. This structure exhibited significant blistering , likely caused by trapped air, moisture fluctuations, or the irregular movement of the tangential-cut wood.

The paint layers remained generally cohesive but suffered from abrasion and lacunae along the edges due to frame friction. These losses created distracting light spots against the dark background. The surface was further obscured by two layers of heavily oxidized, brittle varnish that had yellowed significantly and developed crazing, blanching, and mechanical cracks. Additionally, a thick accumulation of soot, grime, and insect residues veiled the composition and posed a biological risk to the work. Diagnostically, while the painting was stable enough for treatment, the undetermined nature of the blisters required a cautious, research-driven approach to ensure long-term preservation.

The Challenge

Initial dry-cleaning with polyurethane sponges successfully removed loose particulates but left a tenacious, polar-bound grime layer. The objective was to design an aqueous system capable of removing soiling materials without over-wetting the sensitive paper support.

The Decision-Making Process

Analysis and Testing: Surface pH and conductivity were measured to establish baseline conditions. A series of aqueous tests was then conducted within parameters defined by established literature to ensure safety.

Methodology: A citric acid solution (pH 6.5) was formulated and gelled in 1% Methyl Cellulose to increase surface dwell-time and limit lateral spreading or penetration into lower layers.

Clearance: The gel was cleared using deionized water, followed by immediate dabbing with absorbent tissue to further prevent moisture penetration into the support.

The Challenge

The presence of two aged varnish layers necessitated removal due to the risks they imposed on the paint film. While the upper varnish was a later addition, the potential originality of the lower layer required significant caution. Initial attempts at partial removal failed because the lower varnish accumulated within the textured impasto, creating an uneven, yellowed appearance. Full removal was determined necessary to meet the museum’s standards and unified aethetics as it revealed a significant increase in saturation and colour fidelity.

The Decision-Making Process

Analysis and Testing: Solubility tests were performed in both light and dark areas and plotted on a Teas Chart to identify solvents that would effectively solubilize the varnish while remaining outside the high-swelling regions for oil paint. Isopropanol was identified as the most potent candidate.

Methodology: To reduce the risk of capillary penetration and mechanical abrasion associated with traditional swabbing, Evolon® CR and Klucel® G gels were used.

Tactical Refinement: Treatment began with shaped Evolon® CR compresses loaded with gelled isopropanol and covered with Melinex® to control evaporation. When irregular cracking patterns were observed in sensitive yellow and light-brown passages, the methodology was adjusted to further minimize mechanical action.

Monitoring and Control: In sensitive passages, the process transitioned to a brush-applied gel under a stereomicroscope to allow for constant monitoring of the paint’s response. The solvent polarity was also reduced by using a 6:4 Isopropanol:Isooctane mixture to safeguard the paint film while clearing the remaining varnish.

Conservation Ethics: A small area of varnish was left along the right edge for future research, and specific glazes on the whip and cane were preserved to avoid the removal of original material.

The Challenge

Following varnish removal, the painting exhibited uneven gloss and decreased saturation, leaving the paint film physically vulnerable. The primary objective was to apply a protective coating that would saturate the original colours and isolate the original materials from subsequent additions. While an intermediate and a final varnish were initially considered, the minimal retouching required led to the decision to apply only a single layer to minimize intervention. This layer needed to provide protection and a uniform finish without overemphasizing surface blisters through excessive gloss.

The Decision-Making Process

Material Selection: Regalrez 1094, a low-molecular-weight synthetic resin, was selected for its stability and long-term reversibility. To enhance photochemical resistance, Tinuvin 292 was incorporated into the formulation.

Aesthetic Control: To achieve a specific matte finish and avoid accentuating surface deformations, Cosmoloid H80was added as a mattifying agent.

Testing and Evaluation: Six recipes were initially evaluated on a sample painting. Three successful candidates were then tested on the object itself to assess visual performance and handling properties.

The Challenge

The consolidation regime was executed in two phases to address structural instabilities that threatened the integrity of the painting layers and the support. Initial concern centered on the upper right corner, where detachment was feared during the mechanical stress of frame removal. Following the identification of the support as paper, the secondary challenge involved re-adhering detached paper edges to the wooden panel while mitigating the risks of moisture-induced swelling or staining.

The Decision-Making Process

Material Compatibility: For the seventeenth-century preparatory layers, a 10% gelatin solution in deionized water was selected to maintain compatibility with the animal glue likely present in the original ground.

Tension and Penetration Control: To ensure deep penetration of the aqueous adhesive into tight cracks, ethanol was applied as a wetting agent to diminish surface tension. A hot air pen was utilized to assist the flow of the adhesive and accelerate the evaporation of the water carrier.

Solvent-Based Alternative: Upon confirming the paper support, the adhesive was switched to a 5% Klucel® G solution in isopropanol. This modification was made to protect the water-sensitive paper by using an alcohol-based delivery system, effectively limiting the water content during the re-adhesion process.

Mechanical Stabilization: The application process involved precise brush delivery followed by the use of Melinex and weights to provide even pressure during the one-hour curing period, ensuring a flat and secure bond between the layers.

The Challenge

The requirement for visual reintegration was largely minimal. Most losses were concentrated in the dark background, where the exposed support created a stark contrast that compromised visual coherence. A significant loss in the upper right corner required a structural insert to match the thickness and profile of the original paper support. The objective was to reinstall visual uniformity through imitative reintegration while ensuring all materials remained compatible with the sensitive paper and oil-bound layers.

The Decision-Making Process

Structural fill: For the corner loss, acid-free cardboard was selected and cut to the precise dimensions of the missing area. To ensure a seamless transition between the original support and the insert, the cardboard edges were carefully shaved with a scalpel.

Adhesive Selection: Due to the water sensitivity of the paper support, a 5% Klucel® G solution in isopropanol was utilized as the adhesive. This choice effectively limited water content and ensured the adhesive remained soluble in alcohols.

Surface Levelling: To address remaining hollow spaces and imperfect joints at the insert site, Modostuc was applied as a fill to create a level surface for subsequent aesthetic work.

Material Selection and Layering: A base retouch was first applied on the insert using acrylics to establish initial tones. Gamblin Conservation Colours were then selected for the final reintegration. These paints were chosen for their chemical compatibility: they are soluble in alcohols, whereas the underlying Regalrez 1094 varnish remains insoluble.

The conservation project concluded after approximately one and a half years of research and practical intervention. The painting is now in a stable and good condition, following comprehensive cleaning, consolidation, and aesthetic reintegration.

A significant portion of the research focused on structural anomalies in the support; the blisters were investigated in detail, culminating in a discussion at the 2022 online seminar "Seminar on Paintings on Paper Adhered to Other Supports." The collective conclusion determined that the blisters appear stable at the moment. Consequently, it was decided that any structural intervention would be too aggressive and time-consuming for the project's current scope. The painting has been reframed with an acid-free board and a protective backing board to safeguard against dust and mechanical damage. Visual coherence has been restored, allowing the composition to be viewed without the interference of previous degradation.

The Decision-Making Process

Preventive Strategy: Given the blisters' complexity, preventive measures were prioritized over aggressive structural intervention to ensure long-term stability. Strategic lighting decisions have been proposed to minimize the aesthetic impact of the blisters.

Environmental Control: It is recommended to maintain the painting in a dust-free environment with a stable climate to prevent material fluctuations.