ATRIUM AND FAÇADE

The restoration work, begun in March 2000, started with the recovery of the polychrome stucco decorations of the atrium: the sculptural decorations, attributed to the design of Giovanni Battista Castello il Bergamasco, were entirely covered by massive layers of lime-based paints and temperas, moreover oxidised, which blunted the modelling, erasing details and particulars, and hiding the original colour from view: the most recent coat, commissioned by Andrea Podestà in the second half of the nineteenth century, appeared decohesive, very blackened and partially detached.
The removal of the paint layers, carried out by scalpel, revealed, in the blue backgrounds, brush ‘scumbling’ with an almost dry brush, used to render the effect of transparent veiling: here the pictorial retouching with watercolour glazing was essentially aimed at closing the abrasions and colour losses not attributable to the original technique.
Where old integrations were removed, the areas were filled with fine morite based on lime and marble dust.

As cited by Federico Alizeri, the stucco reliefs of the atrium and façade of Palazzo Lomellino, with the exception of repeated paint coats and the inevitable reconstructions due to structural modifications, especially in façadehave maintained over time a remarkable compactness and material cohesion.
The restoration of the decoration of the façade on Strada Nuovarecently completed, now allows the original colouring to be read, essentially based on the contrast between the almost natural colour of the stucco and the slate blue of the backgrounds: the scientific analyses carried out have shown that it is a marmorino with the addition of ‘lampblack’, a pigment of organic, mineral and natural origin, obtained from the combustion of oils, fats and petroleum in limited air, used in painting since antiquity.

The interventions carried out in the nineteenth century by Andrea Podestà, who acquired the palazzo in 1865, must have been essentially limited to the repainting of the façade, as Alizeri notes (1875, p. 190): ‘the front lightened, somewhat darkened by age’. To these interventions should therefore belong the whitewashes found on the stuccoes and the tempera-based repaintings in the monochrome frames of the illusionistic recesses.
During the first site inspection, in the mapping phase of the state of conservation, various detachments were noted, especially near the string courses, probably due to vibrations attributable to bomb fragments that struck the façade, and to rainwater infiltrations.
Another element of degradation was caused by the almost uniform application of a yellow-orange tempera which, having penetrated the first surface layer, had caused patchy staining: this problem was all the more persistent the more the surface was compromised by the loss of the smooth patina.
Reliefs and panels were covered almost uniformly by a layer of dust and carbonaceous deposits which, by blunting the modelling, distorted their reading; widespread erosion phenomena were also noted on the relief surfaces, especially in the festoons of the second floor and notably throughout the band on the right corner, as well as numerous fractures in the modelling caused by the oxidation of internal iron elements, found especially in the most projecting parts of the fruit festoons, in the leonine mascarons and in the panoply at the right end of the first floor.
Widespread detachment, lifting and loss of the fine plaster layer were noted in the panels, on the string courses and on the cornice: the cleaning operations of the entire surface, by means of careful washing with nebulised deionised water, were carried out after the consolidation, by means of semi-fluid injectable mortar, of the above-described parts.
Following the reintegration with lime-based mortar of the losses found after the removal of improper fillings, in order to restore the neutral-slate chromatic alternation, the illusionistic recesses were treated with appropriately pigmented lime-based colour glazes.
All the stone elements of the façade were cleaned using the ‘jos’ system, that is, nebulised jets of low-pressure water (up to 0.2–0.4 atm.) mixed with very fine powdered calcium carbonate, and the marble surface of the portal and balusters was protected with a breathable single-component polymer.

THE NYMPHAEUM

The nymphaeum, being located in an open space, besides constantly coexisting with the presence of water, is also subject to progressive degradation caused by atmospheric agents; but it is precisely the water that makes it subject to a series of alteration phenomena characteristic of these environmental conditions.
The lack of periodic maintenance then contributes to accelerating its deterioration.

The materials themselves, used in the original construction, and worse still, the inadequate ones employed in subsequent interventions, had produced serious conservation problems.
Let us first examine the original materials: the metal elements inside the modelling, serving as supports for natural elements, had progressively deteriorated due to oxidation, and by deforming had caused fracturing or detachment of parts of the modelling, just as they had made the stability uncertain, when they had not also caused the fall of many elements of the natural cladding.
The presence of cement mortars, with particularly high quantities of soluble salts, used in nineteenth- and twentieth-century interventions, had caused the formation of extensive efflorescence that infested the surfaces, disintegrating them.
The numerous invasive shrubs, rooted beneath the plasters, were also a cause of further detachment of the surface mortar layers, just as the widespread presence of bacterial microflora, mosses and lichens caused erosion on the stone and stucco surfaces.
The continuous percolation of rainwater and water from the nymphaeum’s supply along the side walls of the lower grotto led to the formation of substantial limestone deposits.

The cleaning intervention began with careful and repeated washing with demineralised water, and then proceeded, following the removal of the incongruous reconstructions in cement mortars, by means of scalpel.
The fillings and sealings were carried out with mortar based on lime and marble dust, appropriately pigmented, and the entire surface was finally protected with an application of siloxane product.

INTERIOR ELEVATIONS

Observing the surface during the degradation state survey, the heterogeneity of the plaster was immediately noticed, much impoverished by atmospheric agents, except in areas protected by eaves and string courses, where the painted decoration was still present and well preserved; the substrate, as later confirmed by scientific analyses, was covered by a lime and sand mortar (with inclusions of various nature and granulometry), and by a thinner layer of cocciopesto.
The plaster, applied in day sections and scaffold stages, bore a residual pictorial film (fragments of decorations and colour present in areas protected from washing), very compact, with lime-based colours applied to a still fairly fresh substrate.
Numerous fillings and plugs in cement mortar were found, as well as replastering, sometimes of large dimensions, carried out at different periods in the life of the palazzo.

Evidence of one of these phases is certified by the date written on the sub-eaves cornice of the entrance façade (1868), on the band decorated with black and white stencil, covered by the yellow paint: evidently a ‘maintenance’ intervention commissioned by Podestà.
Due to exposure to atmospheric agents and the presence of improper reintegration elements, the substrate showed heterogeneity in application and thickness: the first operation was to remove all those parts reconstructed with unsuitable mortars, and to proceed with deep consolidation, with new integration using lime-based mortar for the lacunae, and with the execution of the cocciopesto finish coat where missing.
At the same time, in order to be able to fully recreate the highly scenic painted decorative scheme, a survey was carried out, first on site and then through graphic design, of all the incision lines present, which were moreover very evident upon close inspection or in raking light.
The entire decorative scheme, recreated by means of glazing with appropriately pigmented lime-based colours, was surface-treated for protective purposes with siloxane water repellent.
The same procedure was followed on the surfaces of the façade facing Palazzo Grimaldi (Tursi): here the decorative repertoire was entirely recreated, documented by the historical photograph found at the Photographic Cabinet of Palazzo Rosso, and fully surveyed from the signs incised on the plaster.