Consolidation and color fixing
The term “consolidation” refers to all those operations meant to re-establish an adequate level of cohesion in materials that have sustained damage at the microstructure level. In addition to interventions on the support (see the sections on lining and mending), consolidation includes the various methods for adhering flaking pictorial film, thereby improving cohesion. These latter operations are frequently referred to as color fixing and color consolidation.
As a protective intervention, the facing of a work often occurs before moving the painting to be treated. This blocks and protects the pictorial film avoiding flaking and loss of material during transportation and subsequent interventions. The facing of a painting involves in the application of an adhesive on the pictorial film protected by special paper that does not contract and is highly absorbent (for example, tissue paper and mulberry paper). Obviously, this adhesive penetrates into the pictorial layers in a non-homogenous manner and does not sufficiently guaranty stability and solidity over time.
Color fixing, adhesive
The loss of adhesion and the flaking off of portions of material from the support is a frequently occurring phenomenon. In general, this material consists of fragments and bits of pictorial film. For various reasons these fragments lose adhesion and flake off. It is therefore necessary to re-establish a stabile condition of the entire structure. Bringing the fragments in contact with the underlying layer or between themselves, an adhesive is employed that can insure stability and permanency.
Color fixing, application method
During the color fixing substances that are capable of creating attractive forces between the two surfaces in contact are used. The methods of application are varied and they depend primarily on the type of adhesives used. The adhesive is classified on the basis of the specific adhesion mechanism: solvent evaporation, chemical process, melting and re-solidification, pressure; or on the basis of its origin and chemical nature: animal, vegetable, synthesis, waxes; or on the basis of the application it is used for.
In the photo shown here a color our fixing treatment is done with the use of a hot spatula.
Color consolidation, consolidant
The need for color consolidation should be evaluated in relation to the cohesion loss in the material and the resulting increase in porosity. This type of intervention requires that the material to be treated be impregnated with a liquid consolidant that can, once penetrated, pass into a solid state and thereby re-establish cohesion.
Color consolidation, application method
Consolidants can be natural in origin (animal, vegetable) or substances resulting from synthesis. The large part of these substances are also adhesives; but consolidants have to satisfy even more requirements: in fact, they have to be able to impregnate the material; they require a slow drying-time; they should be compatible with the original materials, and be chemically and physically stable. They can not have any type of solvent action or reaction with the material being consolidated. Consolidants can be applied in solution, by melting, or they can be monomers capable of being polymerized.
The lack of clarity on the real differences between adhesive and consolidating substances, and consequently on the color fixing and color consolidation operations, has often led to misunderstandings and errors in the interventions. A detailed and clarifying examination of the problem was nevertheless conducted by the chemists Matteini and Moles, from whose text “The chemistry in the restoration” (La chimica nel restauro) the previous quotations are taken.
The conditions of the pictorial film are analyzed prior to applying the protective facing. From this analysis it can be decided if a surface treatment is required. This operation is aimed at aesthetically reducing the surface deformities that may be present due to hard cupping. This intervention can be done using a hand iron, or by means of a suction pump after having treated the pictorial layers.
Estratto da: Manfredi Faldi ,Claudio Paolini, Arte su arte. Una introduzione alle tecniche e al restauro dei dipinti su tavola e su tela, catalogo della mostra didattica itinerante, Firenze Istituto per l’Arte e il Restauro ‘Palazzo Spinelli’, Firenze 1996