23.2 I am here too -The multiform Balsite

30/06/10

For a few years now, CTS, besides the traditional stucco for wood, has promoted and distributed a two-component epoxy-based putty called Balsite, whose basic properties are: remarkable lightness; elasticity; low tenacity; and easy reversibility. These characteristics are closely linked to the particular structure made of micro spheres, as you can see in the picture besides (taken in R & C Art Lab). 

Two recent case studies have examined various properties of this substance and focused on the possibility to turn it into a fluid for injection applications.
This trick can be useful to consolidate fragile artifacts, damaged by Xylophagous insects or affected by microbiological attack. In fact, in some cases, a large part of the woody structure is ruined so much that it looses its functionality and a replacement with a new medium is required. When dealing with wood panels, the transfer of the layer of colors on a new substrate is a very demanding and risky operation. The new woody board and its seasoning state have to be checked because torsional stress can damage the paintings over time. 


In the first study, carried out by Ciocchetti and Munzi for their thesis at the Central Institute of Restoration, and published in the ICR Bulletin No. 15 [1], they focused on the use of Balsite for a specific purpose: making copies of artifacts by injecting the product into silicone resins molds. The outcomes revealed some strengths such as the ability of Balsite to get on well with the movements of wood under thermal hygrometric instability, and the possibility to make adjustments on the surface with watercolors or varnish colors, after a light rubbing with sandpaper. It was also noted a weak point: the resin tends to separate from the inert over time, and deposited on the bottom of the jar. This makes it necessary that you mix the product to homogenize the two phases.

During another case study [2], the restorer Michela Fasce worked out a methodology for the application of Balsite based on the use of the table at low pressure. That is similar to the procedure adopted for the application of consolidation agents in a solution: the object is wrapped in a plastic(for example polyester film) bubble and goes under vacuum treatment. The air is removed from gaps and galleries of xylophagous. Then, the operator perforates the plastic film with syringes and injects the fluid. The consolidant is "pushed" into the empty spaces, and the level of penetration depends on various parameters such as the viscosity of the fluid, the pressure and the type of the material. The results confirm that the Balsite can be used after thinning with solvents. The pressure required for the treatment is related to the thickness of the object; in fact, excellent results are obtained adopting a low pressure on thinner artifacts, while the pressure must be increased to reach the more internal galleries when dealing with thicker sections. It is important you make sure the pressure does not damage the film.

It is important to underline that the parts treated at different pressure conditions, while using the same mixture and the same percentage of solvent, show different arrangement of the resin along the cavities. The parts treated with pressure=120 Pa show that all the tunnels are filled all along the path till to the lower base of the sample, while those treated at 60 Pa have been clogged only in the upper sections. With regard to the solvents, it was noticed that the ethyl alcohol evaporates very quickly, so it can be certainly used for the thinner woody parts (less than 1 cm); this is the procedure adopted for the consolidation of a panel painted at the end of nineteenth century (thickness~ 0.5 cm), with breakthroughs due to the tunnels of xilofagous bugs. The table was kept under a slight vacuum (pressure of 60 Pa), to prevent from crushing of the slim table.

The Balsite seeps into the tunnels and in the areas where it is not visible
, it can be perceived at the touch and the breaches are completely filled in.
For greater thicknesses (where the quick evaporation of the ethyl alcohol increases the viscosity of the mixture and blocks the Balsite at the gates of tunnels), it is recommended to use petroleum oil (with a lower vapor pressure than alcohol) that enables better performances.

Although Balsite shows good 
reversibility, this can be improved with the application of a layer in between, in order to reduce the penetration of a part of the binder within the wood texture. In fact, the strong affinity between the stucco binder and the woody substrate is inherent to the mechanism of adhesion. Excessive penetration can make the putty less reversible, and that's why you can reduce the adhesion by saturating the porous material with a reversible agent, such as Paraloid B-72 or Klucel G, in order to facilitate the detachment of the stucco. A product of this type usually has a consolidating effect too, and this causes the adjacent area between the two phases to be more resistant to tension. With regard to the traditional gilding (' a guazzo'), the surface of the reconstruction is porous, after gently rubbing with sandpaper, and it becomes so simple to prepare the substrate with gypsum, bolus, and finally to gild and burnish with gold leaf. Moreover, the putty is not sensitive to water.

We are going to talk about three cases of great interest:

Plastering of cracked wooden statues [3] _ The operation was conducted by the restorer Gigliola Patrizi on three wooden works of the seventeenth and eighteenth centuries: a sculpture with the Immaculata, in carved wood, painted and gilded, and a pair of carved gilded columns, from South-America, maybe from Spanish areas. The sculptures, very damaged, were consolidated (both the paint film and the underlying support) with Regalrez 1126, diluted at 10% in white spirit (the formulation is now available with 25% of Regalrez 1126; the so called Rexil). Because of its mechanical strength and elasticity, Balsite was used for fillings of greater entity and for a relevant lack of material in one of the two columns. This enables the features to absorb the tensions that may arise in the object, thus preventing from new cracks.The Balsite was applied not only in its pure form but also in the form of fluid (thinned with ethyl alcohol at 5%) and injected into the fissures.
Restoration of a wooden sculpture [4] _ A complex Baroque sculpture with a cherub at the bottom, who originally showed his backside shameless to the viewer. The child had been 'punished' for his exhibitionism with the mutilation of the head and limbs, and then hidden under layers of paint and paper, till to be transformed into a cloud. Later the cherub was replaced by a chaste copy, made of papier-mâché.

The intervention led to the removal of the fake cherub, the 
papier mache and paintings retouchings. The missing parts were rebuilt with clay by copying the papier mache figure. Then they made a silicone rubber mould of the statue and cast the Balsite, taking advantage of the fact that product follows to the small details. Furthermore it is light and easy to be painted.
Creating a layer of interposition between a metallic structure and a polychrome terracotta [5] _ This type of intervention is different from those described so far, and exploits the elastic properties of the product. A terracotta statue representing a Madonna with child, from the church of San Francesco in Citerna (Arezzo), it was rebuilt as a result of the serious damage done in an earthquake. Inside it has been inserted a stainless steel frame, adjustable and removable, which has functions of connection and support.
The upper part of the skeleton steel was incorporated into a form of Balsite, on which rests the sculpture.
The upper internal part of the bust, which corresponds to the area between the neck and the shoulders, had been shaped by a cast made of silicone so that it could adhere perfectly to the surface. This kind of'cushion' acts as a support for the work which, in this way, transfers all his weight on the central body of the structure without stressing any section of the nape of the neck, or on the contact area between legs and torso. Balsite was also used for filling a large gap, and hooked to the structure by means of a magnet. This insert can be removed without exerting mechanical stress, and allowing access to the internal skeleton.

Balsite was also used for the restoration of the cracks of the polyptich by Palma il Vecchio from Peghera. The operations were carried out by Opificio delle Pietre Dure [6] on two panels of "Triptych of Benedetto Portinari" by Hans Memling, Uffizi [7], and the carved wooden polychromatic ceiling of the Church of Santa Maria degli Angeli in Caccamo (PA), fifteenth century [8]. And finally we should mention the consolidation and reconstruction of small fragments of a crucifix by 
Francesco da Sangallo [9].



References
  • Ciocchetti C., Munzi C.; “La Balsite: un nuovo materiale per il risanamento dei supporti lignei e per la realizzazione di parti mancanti” Bollettino ICR n.15, July-December 2007.
  • Fasce M., Borgioli L.;“Metodologia di iniezione di stucchi in opere lignee policrome”, Atti del Congresso “Lo stato dell’arte 7”, Napoli, October 8th-10th, 2009
  • Fasce M., Borgioli L.;“Metodologia di iniezione di stucchi in opere lignee policrome”, Atti del Congresso “Lo stato dell’arte 7”, Napoli, October 8th-10th, 2009
  • Patrizi M.G., Ridolfi S., Carocci I., Borgioli L.; “Tre sculture lignee dorate e policrome: indagini diagnostiche non distruttive ed utilizzo di metodologie e prodotti innovativi a minor impatto ambientale nel rispetto dell’opera, dell’operatore e dell’ambiente”, Atti del Congresso “Lo stato dell’arte 7”, Napoli, October 8th-10th, 2009.
  • Cassiano A., Minerva B., Guarini I., Martignano G.; “Il San Giovanni Evangelista del Monastero delle Benedettine di Lecce: un caso di reintegrazione plastica di una scultura lignea policroma”, Records of the Conference “Lo stato dell’arte 7”, Napoli, October 8th-10th, 2009
  • Shirin Afra “Una madonna con bambino dalla chiesa di S.Francesco a Citerna” Diploma dissertation at Opificio delle Pietre Dure, 2007
  • Castelli C., Cianfanelli M., Ciatti M., Daffra E., Innocenti F., Lallai C., Lanterna G, Moioli P., Parri M., Ramat A., Santacesaria A., Seccaroni G.; “Il restauro Polittico di Palma il Vecchio di Peghera”, OPD Restauro 21 (2009).
  • Buda R., Dori A., Dori L.; “Gli sportelli del Trittico di Benedetto Portinari”, Kermes n°72, 2009
  • Sebastianelli M., Palla F., Mancuso F.P., Rizzo G., Megna B., Di Natale M.C.; “Un soffitto ligneo intagliato e miniato del XV sec. in Sicilia. Studio ed indagini diagnostiche”, Records of XX Conference “Scienza e Beni Culturali”, Bressanone, 2009
  • Teodori B., Fulimeni A, Fioravanti M., Spampinato M.; “Il Crocifisso di Francesco da Sangallo dell’Ospedale di Santa Maria Nuova a Firenze”, Kermes 76, October-December 2009.
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